Pontiac Tri-Power Carburetor Information
 

Some background information:

I worked for the Ford Motor Company, for 39 years, at their Research & Engineering Center in Dearborn Michigan.

Across the street, from the R&E Center is the HENRY FORD MUSEUM of AMERICAN INNOVATION. Inside the Museum is a 1965 Pontiac GTO with a Tri-Power Engine and the hood is open for all to see the special Tri-Power Engine.
A sign above the car says the car represents "POWER".

https://www.thehenryford.org/visit/henry-ford-museum/

I used to eat my lunch inside the Museum occasionally and sat close to the 1965 GTO.
I did not really pay much attention to the car as it was a 1965 GTO and I owned a 1964 GTO.

One day I actually LOOKED at the 1965 GTO engine and noticed that there were several GLARING ERRORS with the way that the 1965 Tri-Power Intake and Carbs were assembled and mounted on the engine.

I spoke with the Curator (manager) of the 'Automotive Displayed' vehicles and told him there were some things wrong with his 1965 GTO.

So we went to look at the car and I showed him each one of the mistakes on the engine.
He was not happy (as they had paid a bunch of money for this 'restored" 1965 GTO.) I will not mention the amount.

So I offered to correct the mistakes on the Engine Tri-Power System.
I would do this for free but I would try to get donations of parts and information from Pontiac people
and from GM Rochester Products Engineering that might be available.

I will not add any thing else to that story except to say that Rochester Products was one of the companies who offered to help with the restoration of the carburetors as well as carb rebuild/ CALIBRATION information.

Pontiac Engineering no longer exists and neither does the Rochester Products carburetor Division,
they disappeared during the GM bankruptcy.

The other thing is Rochester Products Sent Me The Information vs someone stealing the information from a GM location. This was so I could make sure the Carburetor calibrations were "Spot On" for the Museum car and the
1965 Tri-Power system. My daughter, the Lawyer, says I have no issues with providing this info to Pontiac members.

So who would like to know what the real Tri-Power Carb calibrations looked like?
I provided a lot of the Holley Carb Info on the Holley Carbs in another thread.
I worked for Holley and they gave me the "BOOKS" with the info.
This thread would be a similar format.

Once we got past the "interested or not interested posts" I would start the
passing on of the carb info for the 1964, 1965, and 1966 Tri-Power Carb systems.

Post up your thoughts.

Tom Vaught

Start with 66 info!
If I ever have a tripower on a Pontiac engine it will be a 66 setup, mostly because of it highest TP cfm, and being able to use on 65 and newer heads...

One Vote "YES" and a very good suggestion.

Get enough Votes "YES" and B-Man can make the thread a "STICKY" like the Holley Thread.
Then I will just provide the info (with limited posting by others, primarily requests or suggestions like yours).

Tom V.

For sure Yes!

That bankruptcy deal cannabilized a lot of good GM divisions and quite a few good people. Delphi Energy Engine Management Systems is but one example.

Thank you for offering Tom.

Would like to see this, Thanks Tom.

Friend of mine worked for the largest carb rebuilder in the US for GM & was given very large books with all info on every carb listing every spec & Carburetor calibration so that they could build them proper . These are GM master books 10" thick & list every detail on every carb from 1960- 1978 if you may need any info.

Sounds great...would love to see the info on the 65 & 66 Tripower setups.

tr-power
 

sounds great Tom,... Im in.. I hope to use mine on a strong street build one day...

Thanks..

A request has been made to start with the 1966 Tri-Power information, so here it is,
beginning with the Carburetor Part Numbers. Similar info has been posted in bits and pieces in the past so this is a attempt to consolidate some of the information.

1966 389 engines:

Front Carb: 7024178
Front Carb: 7025178

Center A/T Carb: 7026074
Center M/T Carb: 7026075
Center M/T Carb: 7036175* * is A.I.R. Carb - AIR INJECTION REACTOR Carb (Calif.)

Rear Carb: 7024179
Rear Carb: 7025179

1966 421 engines:

Front Carb: 7024078
Front Carb: 7025078

Center A/T Carb: 7026074
Center M/T Carb: 7026075

Rear Carb: 7024079
Rear Carb: 7025079

1) The part numbers for the Rear End Carbs vs the Front End Carbs is 1 number higher.

2) For 1966, the 1966 Tri-Power Carbs basically used the same castings as the 1964 and 1965 castings
as Rochester Products knew that the Pontiac Tri-Power Carb Systems were being discontinued.

3) The Delco/Rochester Products Engineers sent me a 1967 Bulletin 9C-621 (Date May 1967) that replaced 1963 Bulletin 9C-631 (date Oct 1963).

A "handwritten note" note says: "Original Pages from old AC/Delco Carburetor Catalog.
Most Parts are no longer available".
The sheets are labeled:
Delco Rochester Model 2GC Carburetors
There are 3 groups of pages: (1964, 1965, 1966).
Example:

"1966 Pontiac, "V-8"
Triple Two-Barrel Carburetor Installation
389 Cubic Inch Engine

The one I have for the 1966 engine is Bulletin 9C-627
Date May 1967, Replaces 9C-640, April 1966
(For Specifications, see Bulletin 9 PO-1.)
(For Adjustments, see Bulletin 9 PO-3.)

The Delco Information specifically does give you carb rebuild information:

Example (for 1966 carbs)

Front Auto:
Carb Number: 7024178
Replacement PKG No: 22-655A
Overhaul Kit: 7031480
OK Kit: VTR-617
Gasket Set: 40-338
Altitude Kit: 7033029

The information also gives you a Part Number for Every part listed in the kits:
Air Horn Parts, Choke Parts, Float Bowl Parts, Throttle Body Parts, Vacuum Control Parts, and Linkage Parts.

Example: The Link for the long rod that connects the front carb to the rear carb is part Number 7015362. The Rear Clip is number 7011249, and the Front Clip is 554285.
The Water Controlled Vacuum Valve is called a "Thermo Vacuum Lockout Valve" and is part number 7026096.

As Dick B posted, there are literally hundreds of parts and part numbers for the different Tri-Power Systems for just the 1964 to 1966 systems.

Tom Vaught

Do not know what I would ever do with info from 1960 to 1978 on all carbs GM offered. The Tri-Power Systems info will be hard enough to pass on if I leave the Part Number Stuff to builders like Dick B. The Rochester people, as mentioned above, said many of the parts have been discontinued as early as the mid 1970s. I hope to focus on CALIBRATION information.

Tom V.

Now if someone like Dick B or Mike W says, IF I provide the "Carb Calibration" info, it will harm their businesses then I will have to think again about posting up the information.

I would love to see this info So YES

I do not think for a minute that it will hurt Dick or Mike's business. Both gentlemen have already offered up better info for guys engine specs.

Tom - the tripower specifications have been available in the master books as mentioned by chrisp for years. The books were available by subscription to mechanics attending GM schools.

While I cannot speak for either Dick or Mike, I can state publishing these will certainly not harm my business.

An ongoing issue on these (on any other car parts) are supersessions. Rochester would replace a part with a different part, and the new part would show up in the revised specification page. There was a thread on throttle body gaskets with this issue on these forums a few years ago.

I believe you are aware that I posted carb id numbers and casting numbers for the tripower on my website years ago. You are welcome to that information.

For me, the biggest challenge when I was still doing carbs on the tripowers were the various special fittings. We reproduced several of those with more common usage, and even had tooling produced so I could machine inverted flare fittings for those with insufficient usage for mass reproduction.

If your information can provide usage, and especially pictures, of the special fittings, it would be a boon to anyone playing with these.

Jon.

Hello Jon, question for you.
Did the Master books give the exact orifice dimensions for each orifice in the Tri-Power carbs. Holley had calibration Sheets that specified exact calibration orifice numbers for the way the carbs were built. This was for Plant and Engineering use only.

Are we talking about the same information? I have not seen the information you describe in the Master Books for the Tri-Power Stuff. Some say that BG was using the calibration sheets from Holley to build his old stuff. No knowledge of that being true, not my business. But the word was Holley waited until he had built a lot of carbs and then went after the company for each infringement of Holleys info in $$$$.00

Tom V.

From where I am, it would be really nice to have the orifice sizes for the simple fact that over the years these things have been parts swapped, modified, and well meaning “tuners” drilling on stuff.

Would be really nice to be able to quantify what you’re looking at with a specific factory reference to go by to see just where you are with what you have to work with.

Just to be able to return the thing back to original would be wonderful. Performance tuning from that point would be a whole seperate idea, that would take a good portion of a lifetime to teach in and of itself.

An example would be a sizeable box of carbs I “inherited” from a closed tube up shop called “carburetor clinic “ which was a chain in memphis back in the 80’s... they were all disassembled and no telling what was where originally or what had been modified without a good reference.

So they still set in the box waiting some attention.

Tom - not after 1959. Up to 1959, there were additional sheets included that gave this information. And some of the orifice information is contained in the 6B section of the Pontiac shop manuals.

I have seen some of the Rochester plant sheets as you describe on some of the Q-Jets, but not on the 2-G series carbs.

Same is true for other carburetor manufacturers.

Carter probably offered the most complete information to the general public, followed by Stromberg. Autolite probably offered the least information, followed by Rochester (after 1959). Holley and Zenith are in the middle.

You will remember I sent you copies of the Holley 1957 2x4 and supercharged plant sheets, which are the only Holley sheets I have been able to acquire.

Of course, I have all of the Stromberg sheets.

Publishing the plant sheets is a horse of a different color than publishing the MPL sheets. (See PM).

Jon.

I received the "Plant Sheets" from Rochester Products Division on March 5, 1985 in a Rochester Products Division Envelope. There is no doubt in my mind that these are Plant Build Sheets for the Tri-Power Carbs.

Rochester Products Division was sold to Delphi in 1995. That was 25 years ago. A SEPARATE COMPANY, located on the Rochester Products Division property was created to build Fuel Injection Components.

That deal is similar to Borg Warner buying the OEM side of the Holley Carburetor Company that made Air Pumps, EGR Valves, Throttle Bodies, etc.

Holley Performance has/had no control of the Borg Warner owned Holley OEM Production side of the business either.

So I personally believe that I have two legal rights to post the information.
1) Rochester Products Division "Gave Me The Information" (I have that in writing)

and

2) Rochester Products Division has disappeared as far as making any OEM Carburetor Parts just like Autolite disappeared on the Ford Side of the carburetor business.

BUT GM may still own the Copy Right Information still. So I cannot post copies/prints of the sheets but do believe that I might be able to post information on Carburetor "C-1 and C-2" first and then maybe info on Carburetor "A-1 and A-2" and B-1 and B-2".

Tom Vaught

Are we talking about the Delco carb manual; a gigantic "ring binder" with sections for all the various GM carbs? I can't tell, the manuals I have were updated into the 1980s, and go back before 1960.

Far as I know, there was a three-binder set from Delco. If there were other binders covering different subjects, I don't know about them.
1. The Delco "1.2" manual for electrical systems--generators, alternators, batteries, relays, regulators, etc. This was a required text-book for the Auto-Electrical section of my trade school.
2. The Delco "9" Carburetion manual
3. The Delco Brake manual

http://hbassociates.us/Delco_Manuals_01.jpg

http://hbassociates.us/Delco_Manuals_02.jpg

http://hbassociates.us/Delco_Manuals_03.jpg
All the item numbers pictured were referenced to part numbers on the bottom half of the page, and on the back side of the page, for all three carbs. There's a page for every carb, every year, every GM division, plus some non-GM applications, plus Throttle Body Injection. There's sections on the various designs of carbs--Dual Jet, Quadrajet, 2G, etc.

At some point--about 1988, I think--the yearly updates (and perhaps the manuals themselves) were discontinued. Nobody at my local Delco outlet knows anything about these manuals.

At one time I had the folder from when the museum acquired that car.

Like so many things now - I'm not sure what I did with it.

K

No Schurkey, that is a Parts Book not a Calibration Sheet.

Tom V.

In todays world on the internet, copyrights almost seem anachronistic, but corporate attorneys have no sense of humor, and forgiveness is not in their DNA.

For those that may be unaware, copyrights extend for 75 years, and may be renewed by the copyright holder.

Jon.

I have no desire to get into a Copyright War with GM Attorneys, Delphi Attorneys, etc.

I might see if I could get a Disclosure Agreement with the GM Attorneys, Rochester/Delphi Attorneys to post the information.
But that would be down the road or not at all.

Tom V.

For those who have not seen a calibration sheet, information on a specific 4-barrel used on a 421 engine.

Idle circuit:

Jet 0.038
Bypass 0.0595
Economiser 0.055
Bleed 0.0492
Port 0.200 x 0.030

Similar figures were also given for the primary metering circuit, the secondary metering circuit, and the pump circuit.

The bill-of-materials simply gives part numbers for the cluster, the jets/metering rods, and the pump/jet with no dimensions.

Jon.

Agree, Jon, what you posted is a specific idle calibration circuit for a given carburetor part Number.

Tom V.

Schurkey,
Those are what they used to refer to as “Line Manuals”

They have general info such as you give a carb number and they list the jets, metering rods, power piston spring, secondary rods, and any other ancillary numbers such as choke pull off numbers etc.

They do list baseplate numbers, main body numbers, Venturi cluster numbers etc, but no calibration info as was stated above earlier.

Jon Hardgrove created the manifold/carb part number document--I've had it for 35 years or more. It should help people who need info on which manifold is for which year. The carb numbers will help only if the carbs have tags on them, and, even then, there's no assurance that they are the correct tags for the carb they're on. What matters for "correctness" is the casting numbers, which I explain below.

The second document is an exploded view of a '64 Pontiac Tripower with vacuum linkage. Note that the '65 center carb lever extension for mechanical linkage is shown on the bottom right of the page.

I find it interesting that there were only two years where the Tripower intakes had the same casting number--1961 and 1962. Even with the same casting number, some '62's were different in that they had a cast area to install PCV nipples for an "F" fitting.

Also note that the airhorn used on the end carbs is the same casting from 1959 to 1966, casting number 7013206. The float bowls were the same from 1959 to 1963 with casting number 7011997 and from 1964 to 1966 with casting number 7029683. They have slight differences in appearance, but are functionally identical. The 1959 to 1963 throttle bases limited the throttle opening to about 80%, due to the way the throttle stop was machined, whereas the 1964 to 1966 bases allowed full throttle opening. There was a new casting number for the throttle bases sometime in 1966, but I can't see any difference between it and the earlier bases.

I hope this helps you identify parts when you're building a Tripower.

For many years, I never looked at the Spec Cards that closely because the information I was after was for the 1964 Tri-Power System I had. I checked the carbs on the 1965 GTO but did not look closely at the calibrations.

On that page, the people at Rochester Products used a Black "Magic Marker" to cover over the typed statement at the top of the page. I looked at all the documents today and see that the other sheets clearly state:
"THIS SPECIFICATION CARD IS RESTRICTED TO RPD PERSONAL ONLY"
I found a "Cover Letter" from the same people addressed to me, dated March 5, 1985, that gives ME access to the information for use in restoring the 1965 Tri-Power GTO in the Henry Ford Museum. It does not, obviously, say that I am allowed to pass on this same information to others, even 35 years later.

So thinks Jon for getting me to look much closer at the info they sent me.

Looks to me though that the 389 carbs for all 3 years had similar calibrations for ALL of the 49 state vehicles of a given trans type.
The California Vehicles has a very small difference in some cases and that was on UNIQUE Carb Part Number units built with the California required components.

Same trend applies for all of the 421 engines but did not see any 421 California Tri-Power Carb Sheets.

Tom V.

Off the subject...

In all your fact finding information. Do you have much info about the tri power setups that had the single base plate for all 3 carbs? Might be a subject for another thread. I remember Mr McLeller’s OHC cam 421 that WAS in his Gran Prix, had such a carb...

I also read somewhere that Pontiac May have been thinking about trying to use such a unit in 67 to get by with the “One” cab rule.
Thanks for your efforts!!!

The Intake and single carb base for the Tri-Power system you mention, was actually designed by "Mac" and his team several years earlier for his Cammer Engines".

So the "Single Base" system actually "pre-dates" the mentioned "GM Management "One Carb" rule for Pontiac. And yet, the Chevrolet Guys were allowed to continue to offer the HOLLEY "Tri-Power" on that vehicle.

Someone could very well have said, how about we make a single base "Tri-Power" system like "Mac" did on the "Cammers" but that suggestion probably was swept under the rug quickly. Rochester was gearing up for the Quadrajet Carbs for production and would not want that distraction. They were actually getting rid of Tri-power castings, using 64 and 65 end carb parts on 66 systems.

Tom V.


.

Back on the "Calibration" Holes for the Pontiac Tri-Power Carbs.

My opinion after doing the Holley Sticky and having to post a lot of information on what each of the carbs settings did on the Holley Basic Carb: Throttle Plate Position, Transfer Slot Position, Accelerator Pump adjustments, Pump Squirter Sizes, Float Level and Drop settings, jetting, Primary vs Secondary Air Bleed adjustments, etc when you get to the Pontiac Tri-Power stuff, the End Carb calibration is basically the Carb Jetting.

That is unless you are trying to modify Non Tri-Power Rochester 2 BBL Clusters to act like Tri-Power Clusters. Dick B and a couple of other carb Guys already know how to do those mods and have posted info on what they did. The Carb Clone deal I will not go into.

Tom V.

Law also provides a provision for "Fair Use" of copyright material.

Fair Use of Copyrighted Material

Fair use is the right to use a copyrighted work under certain conditions without permission of the copyright owner. The doctrine helps prevent a rigid application of copyright law that would stifle the very creativity the law is designed to foster.

The fair use defense is now codified in Section 107 of the Copyright Act. The statutory formulation is intended to carry forward the fair use doctrine long recognized by the courts. The statute provides that fair use of a work “for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use, scholarship, or research)” is not an infringement of copyright.

One important consideration is whether the use in question advances a socially beneficial activity like those listed in the statute: criticism, comment, news reporting, teaching, scholarship, or research. Other important considerations are whether the use is commercial or noncommercial and whether the use is “transformative.” Noncommercial use is more likely to be deemed fair use than commercial use.

I think you're covered by the Fair Use Clause. :thumbup:

My intent is: Not to make money off the TEACHING/ "Passing On" of Historical Information.

If the Information, Sent to me legally by Rochester Products, (to allow me to configure a Historical vehicle for the Henry Ford Museum to make it correct) then based off of the Fair Use Statute of the law I would assume that means I could Teach other people in the Pontiac Tri-Power Community how to identify
if they have a properly calibrated set of carburetors on their vehicle.

That was the intent, just like in the Holley Thread.

Tom V.

The 1966 Pontiac Tri-Power Carburetors information, as requested.
(For verification of the Carburetor Calibrations that you have on your 1966 Engines.

"A request has been made to start with the 1966 Tri-Power information, so here it is,
beginning with the Carburetor Part Numbers. Similar info has been posted in bits and pieces in the past so this is a attempt to consolidate some of the information.

1966 389 engines:

Front Carb: 7024178
Front Carb: 7025178

Center A/T Carb: 7026074
Center M/T Carb: 7026075
Center M/T Carb: 7036175* * is A.I.R. Carb - AIR INJECTION REACTOR Carb (Calif.)

Rear Carb: 7024179
Rear Carb: 7025179

1966 421 engines:

Front Carb: 7024078
Front Carb: 7025078

Center A/T Carb: 7026074
Center M/T Carb: 7026075

Rear Carb: 7024079
Rear Carb: 7025079

1) The part numbers for the Rear End Carbs vs the Front End Carbs is 1 number higher.

2) For 1966, the 1966 Tri-Power Carbs basically used the same castings as the 1964 and 1965 castings
as Rochester Products knew that the Pontiac Tri-Power Carb Systems were being discontinued."

I will start with the Front Carb: 7024178 I will follow the same format at the Rochester Products People in the way the
information is presented.

Air Horn Number: 7013884 (1)
Venting: Internal 3/16" dia in scoop
External Venting: None
Support: None
Needle Seat: 7027846 Size: .086:
Float Valve: 7022782 Pull Clip: None
Float Assembly: 7012028 Spring: None
Fuel Level: .750" at 6.0 psi
Mech. Setting: .640" Drop: 1.97"
(to sharp edge of seam at toe of float)
Pump Assem: 7020584 (synthetic)
RET Spring: 7004597 Size: .025"
DUR Spring: 7011385 Size: .045"
Pump Rod: 7013276 Length 2-3/4"
Pump Jet: drill (2) Size: .030"
Jet Location: In Cluster
CAP cc/10 strokes: 15.0 - 18.0
Rod Set: .600 from air cleaner flange surface to top of pump rod
Power Piston Assy: None
act spring (blank) Oz Color (blank)
Power Valve Assy: None
Power Rest: None Size: (blank)
Metering Rod: (blank) Spring: (blank)
Rod Size, Power (blank) Econ: (blank)
Cut-In down at: (blank) "Up" at: (blank)

MM. Jets: 390 cc, 60 degree, 7008668 "C"

Choke Housing: None (The next 14 lines available for the Choke Description are blank)

Float Bowl (Finish) Float Bowl and Body Number: 7013258
Venturi Size: 1-5/16"
Cluster: 7016687 Boost Size: 1/8
Nozzle: 7015151 rel zero
Idle Tube: None Size: (blank)
Channel Rest: None Size: (blank)
Hi-Speed Bleed: drill (2) Size: .034
L.I.A.B: None
Idle Bleed: None
Top Bleed: None
Side Bleed: None
Insert: (2) 7008866 (trumpet)
Radial Tubes: (blank) Size: (blank)
Crossover Chan: None Main Well Chan: None

Throttle Body Assem: 7027776 (2*)
Body & Bowl Assem: (blank)
Thr Body No: 7013262 Bore: 1-11/16
Thr Valve: 7027791 Angle 15 degrees
Idle Needle: None
Idle Needle Orifice:
All drilling info is blank

I will finish the document later

Tom Vaught

So here is the last part of the document (mostly just final Info)
Other: 7013264 thr shaft & lever assy
7015106 throttle body gasket

thr shaft offset .027 - .033

no spark port info

Test Specification 7022221

Min Air .95/ lbs min max
Box Balance 18" Hg - 3" Hg
(Note all 2 BBL carbs are tested at 3" of mercury (TV)

Remarks: (1*) 7013249 needle seat screen
7013250 pump shaft & lever assy cast baffle in air horn 7021007 air horn

(2*) 7013783 throttle lever return spring "dag" treatment on throttle valves.
throttle valves in vertical position at wot.

(3*) 7024953 pump squirter deflector installed over cluster

date 9-3-1963
Customer 1964 2G Pontiac 389 cu in A/T & Syn (Front)
Pow. Pak for Pow Pak assys 7024172 & 7024174
Model 7024178 Similar to 7024078

Tom V.

If you copy the info in a Excel or Word Spreadsheet you can combine the info on one page.

This is the info for the Front Carb on a 1966 Tri-Power System from Rochester Products.
Basically, they gave you part numbers and "additions to the basic 2 G carb as well as Flow Test set points.
No different from what Holley did years ago. No magic here.




Spec No 1 (as released)

Info on the 1966 Rear Carb Calibration: 7024179

The 1966 Pontiac Tri-Power Carburetors information, as requested.
(For verification of the Carburetor Calibrations that you have on your 1966 Engines.

I will post the Rear Carb: 7024179 info now. Same format, again, from the Rochester Products People
in the way the information is presented by them.

Air Horn Number: 7013885 (1)
Venting: Internal 3/16" dia in scoop
External Venting: None
Support: None
Needle Seat: 7027846 Size: .086:
Float Valve: 7022782 Pull Clip: None
Float Assembly: 7012028 Spring: None
Fuel Level: .720" at 6.0 psi
Mech. Setting: .640" Drop: 1.97"
(to sharp edge of seam at toe of float)
Pump Assem: 7020584 (synthetic)
RET Spring: 7004597 Size: .025"
DUR Spring: 7011385 Size: .045"
Pump Rod: 7013276 Length 2-3/4"
Pump Jet: drill (2) Size: .030"
Jet Location: In Cluster
CAP cc/10 strokes: 15.0 - 18.0
Rod Set: .600 from air cleaner flange surface to top of pump rod
Power Piston Assy: None
act spring (blank) Oz Color (blank)
Power Valve Assy: None
Power Rest: None Size: (blank)
Metering Rod: (blank) Spring: (blank)
Rod Size, Power (blank) Econ: (blank)
Cut-In down at: (blank) "Up" at: (blank)

MM. Jets: 390 cc, 60 degree, 7008668 "C"

Choke Housing: None (The next 14 lines available for the Choke Description are blank)

Float Bowl (Finish) Float Bowl and Body Number: 7013258
Venturi Size: 1-5/16"
Cluster: 7016687 Boost Size: 1/8
Nozzle: 7015151 rel zero
Idle Tube: None Size: (blank)
Channel Rest: None Size: (blank)
Hi-Speed Bleed: drill (2) Size: .034
L.I.A.B: None
Idle Bleed: None
Top Bleed: None
Side Bleed: None
Insert: (2) 7008866 (trumpet)
Radial Tubes: (blank) Size: (blank)
Crossover Chan: None Main Well Chan: None

Throttle Body Assem: 7027768 (2*)
Body & Bowl Assem: (blank)
Thr Body No: 7025611 Bore: 1-11/16
Thr Valve: 7027791 Angle 15 degrees
Idle Needle: None
Idle Needle Orifice:
All drilling info is blank

So here is the last part of the document (mostly just final Info)
Other: 7013264 thr shaft & lever assy
7015106 throttle body gasket

thr shaft offset .027 - .033

no spark port info

Test Specification 7022221

Min Air .95/ lbs min max
Box Balance 18" Hg - 3" Hg
(Note all 2 BBL carbs are tested at 3" of mercury (TV)

Remarks: (1*) 7013249 needle seat screen
7013250 pump shaft & lever assy cast baffle in air horn 7021007 air horn

(2*) 7013783 throttle lever return spring "dag" treatment on throttle valves.
throttle valves in vertical position at wot.

(3*) 7024953 pump squirter deflector installed over cluster

date 9-3-1963
Customer 1964 2G Pontiac 389 cu in A/T & Syn (Front)
Pow. Pak for Pow Pak assys 7024172 & 7024174
Model 7024179 Similar to 7024079

IT IS INTERESTING THAT THERE IS NO MENTION OF THE MECHANICAL LINKAGE TRI-POWER PARTS ON THIS 1966 APPLICATION


Tom V.

Thank´s for sharing you info Tom V!
In Delco Rochester Bulletin 9C-640 Date December, 1965 #7015106 throttle body gasket (vented) is used for the outer carbs as well as the center cab.
But, in Delco Rochester Bulletin 9C-627 Date May, 1967 (Replaces 9C-640, April, 1966) throttle body gasket #7015345 (not vented) is used.

I have found my 1966 Tripower GTO starts easier hot with the vented 7015106 gasket, but i´m currently using the closed throttle body gasket per the manual.
What was the reason for the change over to the closed gasket?

And, i have not found info for the direct reason on the .030" drilled holes in 1964-66 outer carbs throttle blades, other than keeping the throttle bore clean from "gumming up"?

Looking forward for your info on the center carbs!

1) The "Vented Gasket" works well in warmer climates as when you shut off the engine fresh air fromt the vented gasket has a "Fireplace/Chimney" effect that lets fresh air come into the center venturi section of the carb, pass upward to the air filter, and then disperse thru the air filter to the engine compartment when the engine is shut off after running. Heat and vapors rise.

With the California Emissions Standards, back in the early 60s, the California Carbs went to the closed crankcase system which basically trapped the fumes from the carbs until a restart and then the fumes were burned. The PCV system also allowed burning off the crankcase fumes. Later they used Carbon canisters to trap the excess fumes.

2) Most times when you add a bleed hole in a throttle blade you are adding a place for additional idle air to get into the carb with the throttle blades in the correct relationship to the transfer holes or the transfer slots.
Sometimes you do this is the engine has a larger camshaft and needs more airflow to idle with the extra charge contamination from the extra overlap.

If you just crank up the throttle blade then you screw up the primary blade/ or carb idle function. 4 tiny .030" holes can add a bit more idle air flow even with the throttle blades 'Dagged" so no leakage around the blades.

I personally think they did it because they "dagged" the blades.

Tom V.

That being said, on the rising fumes, if you have a nozzle drip due to a incorrect fuel level in the bowl then the drops of fuel hit the blades. The fumes, then, sometimes exit the same vented cut-outs in the carb gasket.

Tom V.

Kenth - none of the Rochester material I have gives a reason for changing from the vented gaskets to the solid gaskets on the outer carbs.

I will hazzard a guess!

Since the reason for the vented gaskets was to alleviate throttle area pressure blowing additional fuel into the intake past the slightly open throttle plates during hot idle conditions; if one looks at the outer carbs, the throttle plates are tightly closed at idle and off idle. Therefore, there would be no benefit in using the vented gaskets on the outer carbs.

If you remember, you corrected me on these gaskets in these forums a few years ago. I was using the early listing for the bill-of-materials. After our post conversation, I have switched to the solid gaskets on these carbs.

There were never any complaints about using the vented gaskets other than why; to which I then responded with the 1957 Rochester/Pontiac bulletin explaining their use.

Personally, I don't believe there would be any different in driveability with either the vented gaskets or the solid gaskets on the end carbs; but that is conjecture, as all of my GTO's were 1964.

If I still had my 1964, I would convert it back to the single 4-barrel it had originally. I foolishly choose "eye candy" over performance when I converted from the single 4 to the tripower.

Jon.

CENTER CARB 1966 421 engine

The 1966 Pontiac Tri-Power Carburetors information, as requested.
(For verification of the Carburetor Calibrations that you have on your 1966 Engines.


I will post the Center Carb: 7026074 info now. Same format, again, from the Rochester Products People
in the way the information is presented by them.

Air Horn Number: 7031588 (1)
Venting: Internal 7007199 Vent Tube
External Venting: Idle Vent
Support: None
Needle Seat: 7026305 Size: .120
Float Valve: 7022779 Pull Clip: 7006474
Float Assembly: 7012028 Spring: None
Fuel Level: .625" at 6.0 psi
Mech. Setting: .594" Drop: 1.97"
(to sharp edge of seam at toe of float)
Pump Assem: 7032280 (synthetic)
RET Spring: 7004597 Size: .025"
DUR Spring: 7011385 Size: .045"
Pump Rod: 7025575 Length 3.06"
Pump Jet: drill (2) Size: .026"
Jet Location: In Cluster
CAP cc/10 strokes: 18.0 - 21.0
Rod Set: .952 from air cleaner flange surface to top of pump rod
Power Piston Assy: 7012266
act spring 7012265 Oz 8 Color (green)
Power Valve Assy: 7011989
Power Rest: 7010144 Size: (.044)
Metering Rod: (blank) Spring: (blank)
Rod Size, Power (blank) Econ: (blank)
Cut-In down at: 11 "Up" at: 8 all in at 6" hg

MM. Jets: 299 cc, 60 degree, 7008660 "B"
7013333 Idle Compensator Assy:
(140 degree (+ - 10 F) Opening Temp

Choke Housing: (2*) (Some of the next 14 lines available for the Choke Description are blank)
Here are the ones with Info:
Valve No: 7033443 Angle: 20 degrees
Cam No: 7020541
Choke Link: 7019524 Length: 2.671"
wo Kick: .143 - .183 Second Step: .090 .100
Vacuum Break: 25 degrees + - 1.5 degrees (.168 - .192)

Float Bowl (Finish) Float Bowl and Body Number: 7031576
Venturi Size: 1-3/16"
Cluster: 7032380 (4*) Boost Size: 1/8
Nozzle: 7020753 rel .014 - .026
Idle Tube: 7011030 "C" Size: .030
Channel Rest: 7009437 Size: .045
Hi-Speed Bleed: drill (2) Size: .028
L.I.A.B: None
Idle Bleed: None
Top Bleed: .039 over idle tube
Side Bleed: .033
Insert: (2) 7008866 (trumpet)
Radial Tubes: (blank) Size: (blank)
Crossover Chan: .125 Main Well Chan: None

Throttle Body Assem: 7031595
Body & Bowl Assem: (blank)
Thr Body No: 7031597 Bore: 1-11/16
Thr Valve: 7025509 Angle 10 degrees
Idle Needle: 7029605 angle: 20 degrees

All drilling info is blank

Port Punch Length: .250 Width: .030
Port Punch Loc: .233 Top Valve Top Slot
Other: 7032290 throttle body gasket
7020778 thr shaft lever assy
7024885 throttle lever
.055 dia hole in thr valve
thr shaft offset .017 - .023

no spark port info

Test Specification 7022221

Min Air: .65/ lbs min Idle Air rate: .95 lbs min
Box Balance 18" Hg - 3" Hg
(Note all 2 BBL carbs are tested at 3" of mercury (TV)

Remarks: 7013333 idle comp assy
140 degrees F + - 10 degrees F opening temp

(1*) 7021007 air horn gasket 7031590 nut - fuel inlet bend pump lever tang to open idle vent
with .020 gage between thr valve & bore on side opposite idle needle.
(2*) 7026095 vacuum break control assy 7026098 remote choke coil assy
(3*) Service Pump Setting 1-21/64 + - 1/64 from top of die cast air horn ring to top of pump rod
(4*) .026 dia hole aspirator to main well bleed
Note: 7031598 vacuum switch assy

date 3-9-1966
Customer 1966 2G Pontiac (Auto) 421 engine A/C Center

I may do the 1966 Manual Center Carb later but the basic info from Rochester and how they reported the information is there.

If I find significant differences between the Manual and Auto carbs I will post it.

Tom V.

TURNS OUT THERE ARE SOME DIFFERENCES BETWEEN THE PREVIOUS CARB POSTED
and the one I am posting now.

CENTER CARB 1966 421 engine Syn Trans

The 1966 Pontiac Tri-Power Carburetors information, as requested.
(For verification of the Carburetor Calibrations that you have on your 1966 Engines.


I will post the Center Carb: 7026074 info now. Same format, again, from the Rochester Products People
in the way the information is presented by them.

Air Horn Number: 7031588 (1)
Venting: Internal 7007199 Vent Tube
External Venting: Idle Vent
Support: None
Needle Seat: 7026305 Size: .120
Float Valve: 7022779 Pull Clip: 7006474
Float Assembly: 7012028 Spring: None
Fuel Level: .625" at 6.0 psi
Mech. Setting: .594" Drop: 1.97"
(to sharp edge of seam at toe of float)
Pump Assem: 7032280 (synthetic)
RET Spring: 7004597 Size: .025"
DUR Spring: 7011385 Size: .045"
Pump Rod: 7025575 Length 3.06"
Pump Jet: drill (2) Size: .026"
Jet Location: In Cluster
CAP cc/10 strokes: 18.0 - 21.0
Rod Set: .952 from air cleaner flange surface to top of pump rod
Power Piston Assy: 7012266
act spring 7012265 Oz 8 Color (green)
Power Valve Assy: 7011989
Power Rest: 7010148 Size: (.048)
Metering Rod: (blank) Spring: (blank)
Rod Size, Power (blank) Econ: (blank)
Cut-In down at: 11 "Up" at: 8 all in at 6" hg

MM. Jets: 322 cc, 60 degree, 7008662 "C"
7013333 Idle Compensator Assy:
(140 degree (+ - 10 F) Opening Temp

Choke Housing: (2*) (Some of the next 14 lines available for the Choke Description are blank)
Here are the ones with Info:
Valve No: 7033443 Angle: 20 degrees
Cam No: 7020541
Choke Link: 7019524 Length: 2.671"
wo Kick: .143 - .183 Second Step: .090 .100
Vacuum Break: 25 degrees + - 1.5 degrees (.168 - .192)

Float Bowl (Finish) Float Bowl and Body Number: 7031576
Venturi Size: 1-3/16"
Cluster: 7032380 (4*) Boost Size: 1/8
Nozzle: 7012877 rel .049 - .061
Idle Tube: 7011031 "C" Size: .031
Channel Rest: 7011523 Size: .046
Hi-Speed Bleed: drill (2) Size: .028
L.I.A.B: None
Idle Bleed: None
Top Bleed: .039 over idle tube
Side Bleed: .033
Insert: (2) 7008866 (trumpet)
Radial Tubes: (blank) Size: (blank)
Crossover Chan: .125 Main Well Chan: None

Throttle Body Assem: 7031569
Body & Bowl Assem: (blank)
Thr Body No: 7031597 Bore: 1-11/16
Thr Valve: 7008903 Angle 10 degrees
Idle Needle: 7029605 angle: 20 degrees
Idle Needle Orifice: .074 - .078
All drilling info is blank

Port Punch Length: .187 Width: .030
Port Punch Loc: .177 Top Valve Top Slot
Other: 7032290 throttle body gasket
7020778 thr shaft lever assy
7024885 throttle lever
No Hole in thr valve
thr shaft offset .017 - .023

no spark port info

Test Specification 7022221

Min Air: .45/ lbs min Idle Air rate: .55 lbs min
Box Balance 17" Hg - 3" Hg
(Note all 2 BBL carbs are tested at 3" of mercury (TV)

Remarks: 7013333 idle comp assy
140 degrees F + - 10 degrees F opening temp

(1*) 7021007 air horn gasket 7031590 nut - fuel inlet bend pump lever tang to open idle vent
with .020 gage between thr valve & bore on side opposite idle needle.
(2*) 7026097 vacuum break control assy 7026098 remote choke coil assy
(3*) Service Pump Setting 1-21/64 + - 1/64 from top of die cast air horn ring to top of pump rod
(4*) .026 dia hole aspirator to main well bleed


date 3-19-1966 (notice the date change TV)
Customer 1966 2G Pontiac (SYN) 421 engine A/C -NON A/C Center

Tom V.

7024078 Front Carb very similar to 7024178 Front Carb

FRONT CARB 1966 421 engine (A/T & Syn Trans)

The 1966 Pontiac Tri-Power Carburetors information, as requested.
(For verification of the Carburetor Calibrations that you have on your 1966 Engines.

The Front Carb: 7024078 I will follow the same format as the Rochester Products People
in the way the information is presented.

Air Horn Number: 7013884 (1)
Venting: Internal 3/16" dia in scoop
External Venting: None
Support: None
Needle Seat: 7027846 Size: .086:
Float Valve: 7022782 Pull Clip: None
Float Assembly: 7012028 Spring: None
Fuel Level: .750" at 6.0 psi
Mech. Setting: .640" Drop: 1.97"
(to sharp edge of seam at toe of float)
Pump Assem: 7020584 (synthetic)
RET Spring: 7004597 Size: .025"
DUR Spring: 7011385 Size: .045"
Pump Rod: 7013276 Length 2-3/4"
Pump Jet: drill (2) Size: .030"
Jet Location: In Cluster
CAP cc/10 strokes: 15.0 - 18.0
Rod Set: .600 from air cleaner flange surface to top of pump rod
Power Piston Assy: None
act spring (blank) Oz Color (blank)
Power Valve Assy: None
Power Rest: None Size: (blank)
Metering Rod: (blank) Spring: (blank)
Rod Size, Power (blank) Econ: (blank)
Cut-In down at: (blank) "Up" at: (blank)

MM. Jets: 426 cc, 60 degree, 7008671 "C"

Choke Housing: None (The next 14 lines available for the Choke Description are blank)

Float Bowl (Finish) Float Bowl and Body Number: 7013258
Venturi Size: 1-5/16"
Cluster: 7016687 (3*) Boost Size: 1/8
Nozzle: 7015151 rel zero
Idle Tube: None Size: (blank)
Channel Rest: None Size: (blank)
Hi-Speed Bleed: drill (2) Size: .034
L.I.A.B: None
Idle Bleed: None
Top Bleed: None
Side Bleed: None
Insert: (2) 7008866 (trumpet)
Radial Tubes: (blank) Size: (blank)
Crossover Chan: None Main Well Chan: None

Throttle Body Assem: 7027776 (2*)
Body & Bowl Assem: (blank)
Thr Body No: 7013262 Bore: 1-11/16
Thr Valve: 7027791 Angle 15 degrees

Idle Needle Orifice:
All drilling info is blank

So here is the last part of the document (mostly just final Info)
Other: 7013264 thr shaft & lever assy
7015106 throttle body gasket

thr shaft offset .027 - .033

no spark port info

Test Specification 7022221

Min Air .95/ lbs min max
Box Balance 18" Hg - 3" Hg
(Note all 2 BBL carbs are tested at 3" of mercury (TV)

Remarks: (1*) 7013249 needle seat screen
7013250 pump shaft & lever assy cast baffle in air horn 7021007 air horn

(2*) 7013783 throttle lever return spring "dag" treatment on throttle valves.
throttle valves in vertical position at wot.

(3*) 7024953 pump squirter deflector installed over cluster

date 9-3-1963
Customer 1964 2G Pontiac 421 cu in A/T & Syn (Front)
Pow. Pak for Pow Pak assys 7024172 & 7024174
Model 7024078 Similar to 7023078

Tom V.

Lots of differences with this 1965-66 GTO Carb


REAR CARB

The 1966 Pontiac Tri-Power Carburetors information, as requested.
(For verification of the Carburetor Calibrations that you have on your 1966 Engines.


I will post the Rear Carb: 7025179 info now. Same format, again, from the Rochester Products People
in the way the information is presented by them.

Air Horn Number: 7013885 (1)
Venting: Internal 3/16" dia hole in scoop
External Venting: None
Support: None
Needle Seat: 7027846 Size: .086:
Float Valve: 7022782 Pull Clip: 7006474
Float Assembly: 7012028 Spring: None
Fuel Level: .730" at 6.0 psi
Mech. Setting: .640" Drop: 1.97"
(to sharp edge of seam at toe of float)
Pump Assem: 7032280 (synthetic)
RET Spring: 7004597 Size: .025"
DUR Spring: 7011385 Size: .045"
Pump Rod: 7028763 Length 2-3/4"
Pump Jet: drill (2) Size: .030"
Jet Location: In Cluster
CAP cc/10 strokes: 16.5 - 19.5
Rod Set: .600 from air cleaner flange surface to top of pump rod
Power Piston Assy: None
act spring (blank) Oz Color (blank)
Power Valve Assy: None
Power Rest: None Size: (blank)
Metering Rod: (blank) Spring: (blank)
Rod Size, Power (blank) Econ: (blank)
Cut-In down at: (blank) "Up" at: (blank)

MM. Jets: 390 cc, 60 degree, 7008668 "C"



Choke Housing: None (The next 14 lines available for the Choke Description are blank)








Float Bowl (Finish) Float Bowl and Body Number: 7029684
Venturi Size: 1-5/16"
Cluster: 7016687 Boost Size: 1/8
Nozzle: 7015151 rel zero
Idle Tube: None Size: (blank)
Channel Rest: None Size: (blank)
Hi-Speed Bleed: drill (2) Size: .034
L.I.A.B: None
Idle Bleed: None
Top Bleed: None
Side Bleed: None
Insert: (2) 7008866 (trumpet)
Radial Tubes: (blank) Size: (blank)
Crossover Chan: None Main Well Chan: None

Throttle Body Assem: 7029685 (2*)
Body & Bowl Assem: (blank)
Thr Body No: 7025611 Bore: 1-11/16
Thr Valve: 7027791 Angle 15 degrees

Idle Needle Orifice:
All drilling info is blank

So here is the last part of the document (mostly just final Info)
Other: 7029686 thr shaft & lever assy
7015345 throttle body gasket
7029688 Thr Lever
thr shaft offset .027 - .033

no spark port info

Test Specification 7022221

Min Air .95/ lbs min max
Box Balance 18" Hg - 3" Hg
(Note all 2 BBL carbs are tested at 3" of mercury (TV)

Remarks: (1*) pump shaft & lever assy, cast baffle in air horn, 7021007 air horn
Remarks: (2*) 7013249 needle seat screen

(3*) 7029689 throttle lever return spring "dag" treatment on throttle valves.
throttle valves in vertical position at wot.



date 3-26-1966
Customer 1965-6 2G Pontiac GTO 389 cu in A/T & Syn (Front)
Pow. Pak for Pow Pak assys 7024172 & 7024174
Model 7025179 Similar to 7024174

lots of changes on this one TV GTO listed for the first time in the sheets I am posting


Tom V.

I'd like to see the 1965 Calibrations as well. Thank you

We still have several of the 1966 sheets to post and then the 1965 info will be next.
More than a few 65 sheets also. I hope the Pontiac Guys are learning from this exercise.

Tom V.

Is the needle/seat on the 1965 rear carbs the same as 1966 that you have posted ?

The Rear Carb uses the same calibration (same needle and seat, as well as other parts) on the 389 1965 engine and the 389 1966 engine. Carb number 3025179 (Manual Trans Engines).

Tom V.

Tom: Thanks for the quick response. Is the needle/seat available as a nos part, or from parts stores made by other manufacturers?

At one time, the Needle and Seat was available as part of the Rochester Tri-Power Kits
from NAPA. I have not followed those parts for many years. I do not rebuild carbs for people. Dick B, John Hargrove, and others do a fine job with that task.

Being a Holley Guy, I have lots of rebuild parts for the popular Holley High Performance Carbs I own. Somewhere in the shop is ONE SET of NAPA carb kits for my 64 GTO if I ever put the original carbs back on the car. Not likely in the near future.

So maybe too much info vs just saying talk to Dick B, Jon H, and the carb builder in Ohio.

Not my deal. Rochester carbs even though I probably have 100 cores in bins I have collected over the years. I will have to go thru my lists and make a search for correct Air Horns, Main Bodies, and Throttle Bodies for the Tri-Power Systems and put them up for sale.

Tom V.

Perhapes Dick Boneske and John H. might respond to my question !