[62olds]

Hello everyone, I'm new to Pontiacs, recently purchased a 1970 Lemans Sport. I plan on using it to drive to work on nice days. It's 350 2 bbl auto A/C, 129,000 . This is not going to be at full restoration at least of now. I was given a 4bbl intake with a Carter AFB from a 1966 Bonneville. Will it fit on the 70 350 and second is it worth the trouble or should I just pass it on to someone with a 66 fullsize? It will most likely need to be rebuilt as it has been sitting about ten years.
I would like to keep the 350 in the car, just wake it up a little with a cam or head change, thanks for any tips and suggestions.

[ponyakr]

There are guys here who like the AFB. I'm not one of 'em.

I'd go with a Q-jet and either an iron intake or a Performer.

I assume that the 1st 350's to use a Q-jet were the 350HO engines. Last ones were the '77 350's. Those last ones were 800cfm. The early ones were 750cfm.

Those late 800cfm models are considered very good for high performance street carbs. They have the APT feature and can easily be changed over to an elec choke, which many prefer.


"...I would like to keep the 350 in the car, just wake it up a little with a cam or head change, thanks for any tips and suggestions..."

If the rings will maintain a good seal, with a little more cyl pressure, a small Voodoo cam, such as a 250 or 256 should perk it up a bit. But with 129k miles, the extra pressure might be too much for ring seal.

http://www.lunatipower.com/Product.aspx?id=1773&gid=287

http://www.lunatipower.com/Product.aspx?id=1774

Would probably need stronger springs, such as the CC 988-16, assuming a 1.60 installed height.

https://www.ebay.com/itm/Comp-Cams-9...38.m2548.l4275

Cheapest cam is probably the Summit 2800

https://www.summitracing.com/parts/s...RoCijAQAvD_BwE

Obviously, more compression would help. But a cam change is easier/cheaper, than a head change.

Considering the high mileage, it might be best to just try the Q-jet/intake upgrade. At least you can use both on a 400, when the 350 gives up.

Very few decide to rebuild a 350, since it is usually cheaper to build a nice forged piston 400, than a 350 with equal parts. And the 400 will have more low end torque.

Not saying a strong 350 can't be built. It just requires more expensive parts.

http://www.hotrod.com/articles/hppp-...-engine-build/

[tom s]

You already have the intake and carb.NO reason to not use it.AFBs are one of the easiest carbs to tune.You will like it.If you did not already have the setup then the QJ could be a good choice.Pontiac used AFBs from about 1959 to 1967 as I remember.There are people on this board that are experts at tuning AFBs,you will get lots of help.Tom

[62olds]

Thank you, I would like to stay with factory parts.

[62olds]

Yes, eventually it will have be rebuilt or replaced with a 400. My hope was to keep the 350 together as long as possible. The present performance is more than adequate for normal street driving. If costs start to snowball , it makes sense just to find and build the 400. Thanks for pointing out the Lunati cams.

[ponyakr]

Originally Posted by 62olds

Thank you, I would like to stay with factory parts.

Well, I suppose the closest to a factory cam that might work in a low compression 350 might be an 066 clone. I think a Melling SPC-4 fits this description.

https://www.ebay.com/itm/Melling-SPC...pXZx6n&vxp=mtr

https://www.amazon.com/Melling-SPC-4.../dp/B000C4KLKI

Will probably have to use aftermarket lifters.

https://www.ebay.com/itm/New-Hydraul...xZODlz&vxp=mtr

If you go Q-jet, any '68-'72 model Pontiac Q-jet intake will work. My preference would be a '72 model, because it will also work with the '72-up heads, should you use those on a later engine,later on. thepontiacman, on this forum sells lots of Q-jet intakes.

http://forums.maxperformanceinc.com/...d.php?t=808483

I like the '69-'70 Pontiac Q-jets. But, a good clean core can be hard to find & expensive nowadays, especially if it has a number that came on a high performance GTO or Firebird. The early '70's Buick Q-jets seem to be a little cheaper & easier to find. The throttle lever is a bit different, but not a big problem to rig up.

If you go with a '71-'79 or '70 CA model Pontiac Q-jet, it will have a big "smokestack" vent, requiring a hole for it in the air cleaner base. For this reason, some go with an Olds or Buick model, such as a 403 Olds or 455 Buick.

http://everyday-performance.com/test/store.htm

http://quadrajetpower.com/quadrajets...ready-to-ship/

https://www.smicarburetor.com/produc...D2/9/sfID3/100

Most all Q-jet guys recommend avoiding all 1975 model Q-jets.

[Formulas]

That intake and carb should run fine on your 350.
A 350 with 8.8 advertised compression and a stock 254 cam doesnt need any more carb.
At one time i had the same exact motor

[Squidward]

Summit 2800 is a great cam for a street cruising 350. It won't overstress the valve train, sounds good, and will make great vacuum. And it can put your car in the 14's, too.

Cost to build a 350 vs. a 400 is the same, except for the cost to go buy a 400, and THEN start the build. In fact, a 350 might be cheaper since there are cast pistons available that aren't total POS's with 8 valve reliefs...
https://www.summitracing.com/parts/s...w/make/pontiac

It just depends on what your aspirations might be for the 350. Many people tend to overbuild for their intended usage, and the mild Dairy Queen cruiser ends up with forged spendyourmonium everything making 600hp.

I've never played with an AFB. I would default to qjet or Holley style as my first instinct. I like both of those for different reasons.

I'm an FiTech guy now. I am enjoying modern tech and convenience now that the price point is so awesome.

[Tom Vaught]

AFBs with a PONTIAC CALIBRATION are some of the nicest driving carbs on the street. The Rochester Products people really have good carbs but I personally also like the CARTER "Pontiac" FACTORY AFBS. Very easy to tune as was said, and will work fine for your application.

Leave the Q-Jet and Holley off of this one.

Tom V.

[steve25]

Just note that since that Carb came off a motor that is 7% smaller it may need to be jetted different on the secondary side, and if your A body has true duel Exh then you will without question want to richen up the secondary jetting!

Most of those AFB Carbs seen to like 3 to 3 1/2 turns out on that big center air mixture screw, as sometimes previous owners have set them way off!

[Tom Vaught]

Believe only air goes thru that Air By-pass passage past the screw Steve. No Mixture.

It is kind of like the "Grandfather Carter" of the later Barry Grant "Idle- Eze" system which also supplies only air to the engine.

Tom V.

[steve25]

True, but that it does pass idle air if I recall right and I have come across some of these Carbs on motors where the owner adjusted them way out because it seemed to be the thing to do since it raised the idle speed .

[61-63]

Since the cubic inches are less he will need to install larger metering rods to reduce the flow slightly through the primary jets. He can leave the secondary jetting as is. Initial setting on the big bypass screw can be all the way in and then 1 1/4 turns back out and then on the idle mixture screws all the way in and then 2 turns back out and if it won't idle smoothly turn the idle mixture screws out some more 1/2 turn at a time. To increase idle rpm back the big screw out and to reduce idle rpm turn it in.

With the same jetting in the secondaries he may be a tad rich when his foot is all the way in it but as we all know rich is better than lean.

[carbking]

I would suggest three modifications when rebuilding the AFB:

(1) The original specs for the AFB for 389 idle tubes were 0.035 and for the 326 0.038 (smaller engine, less venturi velocity, MORE fuel required). Drill the idle tubes 0.038 inch.
(2) Look at another AFB with the conventional idle circuit (no idle air mixture screw). The boss for the throttle positioner screw is present, just not drilled. Drill and tap for a number 10 x 32 machine screw, and install a throttle positioner screw. Then, when adjusting, turn the air screw all the way in and leave it, and adjust the idle with the throttle positioner screw. The air screw worked very well with real gasoline. It can be a bear on a stock engine and modern fuel. VERY useful tool, however, with a big cam and the throttle positioner screw.
(3) John (61-63) is right-on about the rods; but the necessary rods are unique to the 326 HO carb, and fairly scarce. Unless you have a lathe that will cut metering rods, as I do, much cheaper and almost as good to compensate with slightly oversize primary jets. Originals were 0.0935. 0.095's are fairly common, and should be very close to the 326 calibration when used with the original rods.

As John mentioned, secondaries should be fine.

If a high mileage carb, make sure you replace the vacuum pistons (they come in the good carb rebuilding kits).

Jon.

[PunchT37]

Originally Posted by Tom Vaught

AFBs with a PONTIAC CALIBRATION are some of the nicest driving carbs on the street. The Rochester Products people really have good carbs but I personally also like the CARTER "Pontiac" FACTORY AFBS. Very easy to tune as was said, and will work fine for your application.

Leave the Q-Jet and Holley off of this one.

Tom V.

I agree with Tom. It`s not a Edelbrock copy with a chevy tune.

Throw it on as is and see how it runs. It might run fine with the "389 tune". If it doesn`t, then follow the advice of the others with carb experience in this thread.

[62olds]

Originally Posted by Formulas

That intake and carb should run fine on your 350.
A 350 with 8.8 advertised compression and a stock 254 cam doesnt need any more carb.
At one time i had the same exact motor

I will try this setup and see what happens, I can always reinstall the 2bbl. Any recommendations for intake gaskets? Should I use the heat block offs?

[tom s]

for your street car and where you live I would say dont use the block offs.Pretty much any make gasket should be fine.Tom

[carbking]

Originally Posted by 62olds

I will try this setup and see what happens, I can always reinstall the 2bbl. Any recommendations for intake gaskets? Should I use the heat block offs?

The second worst mistake I have ever made in over 55 years of working on automobiles was blocking the heat cross-over on my Pontiac 350!

Jon.

[Tom Vaught]

Tri-Power Manifolds were cheap and farmers could weld cast iron very well in those day.

So I removed the Exhaust Manifolds and put on Headers. Then I had the Local Welder make a couple of plugs and we welded the plugs permanently into the Tri-Power intake flanges.

Then, when it got cold, I plumbed the heater circuit, thru the intake cross-over, (that was plugged) and on to the heater core.

Finally I bought a Radiator Hose Heater, that you plugged in the wall plug, that kept the water in the engine warm so now the engine started easier (no choke), the heater worked quicker, and the intake stayed warmer, and I had all of that power from the Headers. LOL!

Boy, was I dumb, should have left everything stock.

Tom V.

[62olds]

Thanks to everyone who took the time to reply. I apologize in advance if some future questions seem fairly basic?