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Old 08-16-2022, 06:54 PM
tom s tom s is offline
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As your going to be driving this engine I would be concerned on what the shear plated would do to street manner.As its made it has great street manners.If you have them to be able to be put in a taken out with removing the carbs it might show you something.I DONT drive mine on solid linkage.Tom

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Old 08-16-2022, 07:13 PM
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As your going to be driving this engine I would be concerned on what the shear plated would do to street manner.As its made it has great street manners.If you have them to be able to be put in a taken out with removing the carbs it might show you something.I DONT drive mine on solid linkage.Tom
As it sits on the dyno, it has 1:1 linkage. It seems very smooth and snappy on the primaries but in the car it could be different of course. The in the car linkage will have the ability to run 1:1 or progressive by changing 1 link. So I can play with it. I am impressed with the stable, idle at 900 RPM with a pretty big camshaft. It's 251, 259 @ .050, solid flat tappet. Idles within a 25 RPM range as long as you want it to.

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  #43  
Old 08-16-2022, 09:28 PM
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I ran a 255/260 Solid Flat Tappet for years on the street, Obvious Noticeable Idle but never had any hesitation with the vehicle on the street or the road.

IT WAS NOT A TAKE A TRIP camshaft though.

Drove 150 miles from Kalamazoo Michigan to Grosse Pointe Michigan and almost ran out of gas.
Oh! What fun, running along at 3000+ rpm with Wangers 4.33 rear gear under the car at 55-60 mph.

The NASH TRANS (5 speed) and the proper Ford Gear in the 9" really helped that deal.

So as you know Mike, drive-line match will be worth investigating if you take the car on trips.

Have a great evening!

Tom V.

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Old 08-17-2022, 08:05 AM
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It has a 3.42:1 gear now and runs 2800 @ around 70 MPH Would like to change to a TKX 5-speed, will have to wait for some more $$$. Also would like to drive the Power Tour long haul route with it possibly next year. Confirmed next dyno session will be Thursday afternoon/evening.

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Old 08-18-2022, 08:10 PM
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Unfortunately, no results to report. Had to cancel due to parts issues. The two strip kits I ordered from Summit that had the rich jets and metering rods in them had been opened. The exact metering rods I needed had been stolen from both kits and then the kits returned. The tamper resistant tape was missing from one and torn on the other. So someone took what they needed, and returned the kits to Summit. Shame on them for just re-boxing them and selling them again! No more kits available in the US. But I have the rods I want to try coming from Memphis. They were shipped today. Have the spacers installed. This thing is fighting me every step of the way. Sorry for the delay.

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Old 08-30-2022, 10:18 AM
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I have some results to share concerning multiple dyno sessions I have had to squeeze in between classes and all kinds of other problems and distractions over the past couple weeks. Between parts getting lost by USPS for 2 weeks, endless problems with the dyno, printers specifically, and other distractions too numerous to list. I have been able to get 26 power pulls on the engine and get it tuned decently for now. I will consolidate the useful information, try to get it in a format I can post and put it up in the next week. These are my broad takeaways for what it's worth. 1. My overall engine package had too many compromises that were made necessary by not wanting to wait for years for the proper parts to be available. 2. This package needed more compression, round port exhaust and better exhaust manifolds/headers. 3. The bathtub intake wants lots and lots of fuel. 4. AFB carburetors are very, very sensitive to what is happening above the airhorn. Will flat out not run properly with an air hat on the top. I have seen this with some Q-jets as well. 5. Long branch, D-port, iron manifolds are crap on a serious performance engine with large displacement. They are just too small.

Now for some numbers: Best with exhaust manifolds, 464.6 Ft. Lbs @ 4700 rpm Peak HP 442.2 @ 5900 rpm. With borrowed 1 3/4 headers from a 74 GTO NHRA stocker: 18" long 3" collector, 481.6 ft. lbs torque @ 4800 rpm. 20-28 more ft. lbs. of torque everywhere. 448.4 HP @ 5800 rpm. Was not tuned to the headers, so 10-15 HP more on top could be expected. No reason to tune to headers because they are not going to be used.

So I have presented the basic results. Since I have no ego to care about, it is what it is. Overall a frustrating, humbling experience. Sometimes, you just get a reality check when having to make so many compromises for the lousy pump gas, the fitment in the chassis, (exhaust manifiolds), and the super cool looks, bathtub intake and original looking AFB carbs with tiny air filters.
On the plus side, excellent idle quality, starts quick and easy, snappy throttle response, seems like it will have excellent street manners. Anticipate using lots of gas. It runs best at 12.4-12.7 AFR everywhere. Starts to run lousy leaner than 13.2-13.4 AFR. It loves fuel.

Going to put it in the car and drive it around through the fall here in Ohio. We have a chassis dyno at the school, so in the spring, I may try to do some tuning on the chassis dyno. That's more real world and the AFB carburetors can operate in their real world environment. That will be chapter 2. We will see how it runs on the street next.


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Old 08-30-2022, 11:57 AM
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Good info Mike, thanks for sharing. You might consider the Hooker headers that are are on super sale right now. As far as I know, they “should” fit a ‘62 full size as well as 1st generation Firebirds. At the price, it’s worth a shot. I have a nice set of original IA headers for my ‘63 that fit great.
Looking forward to hearing how it drives in the real world.

https://www.holley.com/products/exha...arts/4107-1HKR

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Old 08-30-2022, 12:52 PM
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Good info Mike, thanks for sharing. You might consider the Hooker headers that are are on super sale right now. As far as I know, they “should” fit a ‘62 full size as well as 1st generation Firebirds. At the price, it’s worth a shot. I have a nice set of original IA headers for my ‘63 that fit great.
Looking forward to hearing how it drives in the real world.

https://www.holley.com/products/exha...arts/4107-1HKR
Thanks for the info. Those headers are a smoking deal. I saw you had nice custom headers on your car in another thread. I am married to these boat anchor iron manifolds for now at least. I have a grand in them not counting the rest of the exhaust system. My goal was to have the car be pretty quiet, so I have only a 2 1/2" system all the way back with the largest case performance mufflers I could find. While the F body headers would be a bolt-in on the right side, the big cars have the steering box in quite a different location from the F body. Also clutch linkage would be in the way probably, not sure. Just not willing to go there right now. Also, to really be optimized using my current heads and cam, I think I need 1 7/8 or 2" primary tubes. The Hookers are 1 3/4". What size is your engine and the primary pipes for reference? Also approximate cam specs. of you will share. Thanks for posting.

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Old 08-30-2022, 01:05 PM
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Early firebirds are rear steer, same as early full size. The long branch fit both cars so I don’t think the headers could be that far off. My headers are 2” with 3 1/2” collectors. Have not measured the length. I don’t want to clutter this thread with other info, just sharing header info. BTW, I committed to a 671 way before this intake was in the works so my intake is for a possible future build.

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Old 08-30-2022, 03:16 PM
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I don’t know if you folks have ever seen this guide chart for exh header tube size, but I have found it extremely accurate!

The only tempering I add to this is if I need more exh flow then the port is providing in order to get the exh to intake ratio better .

Any exh port I have ever worked with of any make on my flow bench ( and even long ones like Pontiacs ) will pick up 3 to 5 percent more cfm above .350” lift if the header tube that bolts to the exh flange is 1/8” larger in it’s perimeter.

This why especially with a race motor that the exh side is flow tested with at least a 6” long tube in place.
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Old 08-31-2022, 09:12 AM
mgarblik mgarblik is offline
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I don’t know if you folks have ever seen this guide chart for exh header tube size, but I have found it extremely accurate!

The only tempering I add to this is if I need more exh flow then the port is providing in order to get the exh to intake ratio better .

Any exh port I have ever worked with of any make on my flow bench ( and even long ones like Pontiacs ) will pick up 3 to 5 percent more cfm above .350” lift if the header tube that bolts to the exh flange is 1/8” larger in it’s perimeter.

This why especially with a race motor that the exh side is flow tested with at least a 6” long tube in place.
That chart is proof positive that the long branch exhaust manifolds are not up to the task on a good flowing head. I did not have a chance to flow the CNC ported E-heads on the engine, but I would feel safe saying the exhaust flow around 240 + CFM max and 225 + at my max valve lift. That puts me at around 2" primary tubes as stated in an earlier post. The long branch manifold on the left side that jogs around the starter has areas where I bet the passage is 1" to 1.25" maximum. Unfortunate, but the ease of packaging a manifold vs tube headers is a compromise each user needs to assess for themselves I guess.

I made final pulls last night with manifolds in place again. No changes in set-up. Started pull at 180 degrees and the engine repeated within 1% of best previous pull last week. Don't remember the exact numbers but torque approx. 468 ft Lbs +- @ 4800 rpm and HP 446 @ 5900 rpm. Pulling it off in a few days and getting it ready to install. Once I can get the files off the computer or actually get a printer to work, I will post more details for anyone interested. The ancient computer that runs the dyno has a broken CD drive and no working USB for a flash drive. It's always something.


Last edited by mgarblik; 08-31-2022 at 09:23 AM.
  #52  
Old 09-01-2022, 12:24 PM
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I hope you don't mind me jumping in here with what I think are questions related to the subject being discussed. I do not have a bathtub intake, but I am building a pair of SD clone carbs from a pair of 2840S AFB's ('59 Buick 401). My biggest concern is regarding the weight of the secondary air flapper valves. Seems to me that with half the volume of air passing through each carb at any given RPM (compared to a single carb), it's going to require considerably more RPM (twice?) to fully open the air valves.

Any thoughts on how to go about scientifically and methodically fine-tuning the air valves? Is the shape of them all the same and the only changes are to the counter-weights? Perhaps you do indeed want to delay the secondary air valve opening somewhat in a dual carb setup to avoid low velocities and poor atomization?

The jetting can be worked out in a straight-forward conventional manner, but the transition of the primary circuit enrichment for decent street manners is another matter. I think getting the spring just right is going to be hard.

I'd appreciate any and all thoughts and comments.

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  #53  
Old 09-01-2022, 01:45 PM
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61-63 61-63 is offline
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FYI as you may know I've done a number of those carbs for people over the years, over ?? eighty sets at this point. For 389 through 535 cubic inch engines using the 2840 carbs you have as well as '59 Buick 2982s as well as 3221 and 3012 Chevy 348 carbs and one set using 2955 Crusader marine carbs. On the vast majority of these sets I installed the secondary air valves that originally came with the carbs back in both carbs. On a few sets I installed a lighter (in weight) valve in the front carb, under the theory that it would observe a weaker signal when it began to open than did the primary carb which opened up first. Most of the 3221 and 3012 (and the 2955s) had the same valves as do the 3010, 3266, and 3433 and 3435 SD carbs which by the way have the same weight valves in both carbs. I have NEVER gotten a comment from any customer re problems with valves opening up as they stabbed the gas pedals. Most of the sets I've done are on show or cruise in cars but at least four sets are on Nostalgia Super Stock cars and no comments from them either. More than one of the 389 engine owners I did the above sets for told me they could get rubber in third gear with their new dual quad setup and they were never able to do this with the tripower set they had before they installed the dual quads. My recommendation to you would thus be to put the original secondary valves back in both carbs and see what happens. If you see a bog, not a hesitation but a kind of ?? dull momentary pause where the engine seems to dag on at one rpm before going on up higher, then take the front valve out and drill a hole at the front edge of both weights and try again and see what happens.

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Old 09-01-2022, 01:46 PM
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Quote:
Originally Posted by 25stevem View Post
I don’t know if you folks have ever seen this guide chart for exh header tube size, but I have found it extremely accurate!

The only tempering I add to this is if I need more exh flow then the port is providing in order to get the exh to intake ratio better .

Any exh port I have ever worked with of any make on my flow bench ( and even long ones like Pontiacs ) will pick up 3 to 5 percent more cfm above .350” lift if the header tube that bolts to the exh flange is 1/8” larger in it’s perimeter.

This why especially with a race motor that the exh side is flow tested with at least a 6” long tube in place.
Haven gotten flow number from people like Darin Morgan I have found that they do not flow the exhaust with a pipe.

While I don't know how well that formula works. He does state there is a range for FD of from 80 to 90. The Graph uses 80 which produces a larger pipe size than 90 will.

We can see at 160 cfm the difference is a little over 0.09" in diameter
► cfm=160
► ((cfm*1.27)/80)^.5
1.59374
► ((cfm*1.27)/90)^.5
1.50259

Stan

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  #55  
Old 09-01-2022, 02:01 PM
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Originally Posted by 61-63 View Post
FYI as you may know I've done a number of those carbs for people over the years, over ?? eighty sets at this point. For 389 through 535 cubic inch engines using the 2840 carbs you have as well as '59 Buick 2982s as well as 3221 and 3012 Chevy 348 carbs and one set using 2955 Crusader marine carbs. On the vast majority of these sets I installed the secondary air valves that originally came with the carbs back in both carbs. On a few sets I installed a lighter (in weight) valve in the front carb, under the theory that it would observe a weaker signal when it began to open than did the primary carb which opened up first. Most of the 3221 and 3012 (and the 2955s) had the same valves as do the 3010, 3266, and 3433 and 3435 SD carbs which by the way have the same weight valves in both carbs. I have NEVER gotten a comment from any customer re problems with valves opening up as they stabbed the gas pedals. Most of the sets I've done are on show or cruise in cars but at least four sets are on Nostalgia Super Stock cars and no comments from them either. More than one of the 389 engine owners I did the above sets for told me they could get rubber in third gear with their new dual quad setup and they were never able to do this with the tripower set they had before they installed the dual quads. My recommendation to you would thus be to put the original secondary valves back in both carbs and see what happens. If you see a bog, not a hesitation but a kind of ?? dull momentary pause where the engine seems to dag on at one rpm before going on up higher, then take the front valve out and drill a hole at the front edge of both weights and try again and see what happens.
Great information. Thanks, John!

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  #56  
Old 09-01-2022, 02:17 PM
mgarblik mgarblik is offline
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Originally Posted by tekuhn View Post
I hope you don't mind me jumping in here with what I think are questions related to the subject being discussed. I do not have a bathtub intake, but I am building a pair of SD clone carbs from a pair of 2840S AFB's ('59 Buick 401). My biggest concern is regarding the weight of the secondary air flapper valves. Seems to me that with half the volume of air passing through each carb at any given RPM (compared to a single carb), it's going to require considerably more RPM (twice?) to fully open the air valves.

Any thoughts on how to go about scientifically and methodically fine-tuning the air valves? Is the shape of them all the same and the only changes are to the counter-weights? Perhaps you do indeed want to delay the secondary air valve opening somewhat in a dual carb setup to avoid low velocities and poor atomization?

The jetting can be worked out in a straight-forward conventional manner, but the transition of the primary circuit enrichment for decent street manners is another matter. I think getting the spring just right is going to be hard.

I'd appreciate any and all thoughts and comments.
I can address your question slightly. I ran all my dyno pulls with the supplied air valve. There is no spring involved with the air valve on an AFB. Just the valve, shaft and the two counterweights. My original plan was to mount a GoPro camera above the carbs and take some video of a pull. With all the Chaos I had with the dyno, air hat, tuning, O2 sensors, and printers, it just never happened. I thought about just using my phone and filming holding the camera. As much as I trust my ability to put an engine together, standing right next to it holding a camera at 100% load at 6000 RPM's didn't seem smart. I am confident in my case, the air valves open completely and quickly when the throttle is opened. You can see it by a dip and recovery in the torque curve. I can also say now that AFB's are the most sensitive carburetor I have ever worked with concerning the air flow through the carburetor. My AFB clone SD carbs are not identical. The rear carb has the choke shaft and butterfly. The front, no choke. The front carb flows about 8-10% more air than the rear. I found that interesting. So I swapped the air horns front to rear. Then the rear carb flowed 8-10% more air than the front. The choke shaft which is right above the primary venturi cluster, blocks 10% of the air flow through the primary along with the butterfly. Much more than I expected. A real learning experience. I think anyone able to extract maximum performance from them in a nostalgia super stock car is some kind of magician. I talked to so many people over the last several months about tuning dual AFB's for racing, Mopar, Chevy and Pontiac. Every single person I talked to said it took a ton of work and many, many runs on the drag strip to optimize them. Dyno tuning would only get you in the ballpark. Tuning for the street was pretty straightforward. For the street, they would set them up a little rich and enjoy them.

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Old 09-01-2022, 03:21 PM
tekuhn tekuhn is offline
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Originally Posted by mgarblik View Post
I can address your question slightly. I ran all my dyno pulls with the supplied air valve. There is no spring involved with the air valve on an AFB. Just the valve, shaft and the two counterweights. My original plan was to mount a GoPro camera above the carbs and take some video of a pull. With all the Chaos I had with the dyno, air hat, tuning, O2 sensors, and printers, it just never happened. I thought about just using my phone and filming holding the camera. As much as I trust my ability to put an engine together, standing right next to it holding a camera at 100% load at 6000 RPM's didn't seem smart. I am confident in my case, the air valves open completely and quickly when the throttle is opened. You can see it by a dip and recovery in the torque curve. I can also say now that AFB's are the most sensitive carburetor I have ever worked with concerning the air flow through the carburetor. My AFB clone SD carbs are not identical. The rear carb has the choke shaft and butterfly. The front, no choke. The front carb flows about 8-10% more air than the rear. I found that interesting. So I swapped the air horns front to rear. Then the rear carb flowed 8-10% more air than the front. The choke shaft which is right above the primary venturi cluster, blocks 10% of the air flow through the primary along with the butterfly. Much more than I expected. A real learning experience. I think anyone able to extract maximum performance from them in a nostalgia super stock car is some kind of magician. I talked to so many people over the last several months about tuning dual AFB's for racing, Mopar, Chevy and Pontiac. Every single person I talked to said it took a ton of work and many, many runs on the drag strip to optimize them. Dyno tuning would only get you in the ballpark. Tuning for the street was pretty straightforward. For the street, they would set them up a little rich and enjoy them.
It's very possible the counter-weights on the air valve influences the SPEED of the valve opening much more than they set the air flow at which it opens. I'm convinced at this point to just start with what I have and see how well it works. Thank you for the information.

BTW, the spring I was referring to is the one under the metering rod piston that determines the vacuum level required to transition from the richer to leaner primary mixture.

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  #58  
Old 09-01-2022, 03:38 PM
mgarblik mgarblik is offline
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Originally Posted by tekuhn View Post
It's very possible the counter-weights on the air valve influences the SPEED of the valve opening much more than they set the air flow at which it opens. I'm convinced at this point to just start with what I have and see how well it works. Thank you for the information.

BTW, the spring I was referring to is the one under the metering rod piston that determines the vacuum level required to transition from the richer to leaner primary mixture.
Ah, yes. I played with this a little on the dyno. My goal was to make sure I was on the fat area of the rod, ie, rod down, while cruising at light highway speed. Had to just guestimate the load. I was able to get low 13-13.2 to 1 AFR at 20% load and 3000 RPM's. Car runs 3000 @ 70 mph. They are so easy to change , I will tune once in the car. I love that feature. Primary metering rod and spring change in 5 minutes on 2 carburetors. Now that is a very smart design.

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Old 09-01-2022, 03:53 PM
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Ah, yes. I played with this a little on the dyno. My goal was to make sure I was on the fat area of the rod, ie, rod down, while cruising at light highway speed. Had to just guestimate the load. I was able to get low 13-13.2 to 1 AFR at 20% load and 3000 RPM's. Car runs 3000 @ 70 mph. They are so easy to change , I will tune once in the car. I love that feature. Primary metering rod and spring change in 5 minutes on 2 carburetors. Now that is a very smart design.
Yes indeed. I really like AFB's. Only one I've ever owned before now was on a '67 Buick 340 that I pulled from a salvage yard Gran Sport and transplanted into my '64 LeSabre in place of the worn-out 300 2-bbl. A direct bolt-in. That was in 1976.

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  #60  
Old 09-02-2022, 10:11 AM
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The jets in my carbs do not follow the standard naming convention with the last 2 digits being the opening size. Does anyone know where to find a chart showing the size of these jets?

#120-166 Primary
#120-222 Secondary

The metering rods are #16-82X and measure .060 and .067, although there is some variation in them.

Thank you!

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