1973 Buick Apollo 350 Engine

[ljrsports]

Hello to all,

I'm new to the Forum World and hope someone can give me some good advice. I have a 1973 Buick Apollo with the original 350 Engine however , 10 years ago I rebuilt the Engine and installed hi compression Pistons and a Comp Cam. The problem I have is when I had installed a factory 4 barrel intake and 750 Q-Jet 4 barrell Carb the Engine felt like it was flooding out when the pedal was stomped to the floor. With the stock 2 barrel it runs good. But I really want to go to a 4 barrel Intake , 4 barrel Carb and some Headers for more Horses. Any suggestions?

Thank You

[raycow]

Does this problem occur at all engine speeds or do you see it only at low RPM?

Ray

[ljrsports]

Ray,

Thank You for responding. The problem only occurs when I stomp the pedal to the floor at any speed. I am real sure it flooded each time because I would have a hard time restarting it. I had tried an after market intake and a holly double pumper but the same thing would happen. I desided to go back to the factory 2 barrel and it runs great but I know I could get alot more Horses by adding to my Engine.

Leo

[raycow]

Will the engine stand full throttle if you floor the gas pedal slowly?
Also, what kind of transmission does the car have, and does it have a tach?

Ray

[ljrsports]

Ray, I have the original Hydro-matic transmission (rebuilt). No problems in park goosing the engine full open but not in drive. Tach not working. Lots of other posts recommend a 500cfm Carb but with the flat top pistons and the hot cam I figured it would have no problem with a big carb. Runs great with the original Rochester 2 barrel but I am at a point where I want to really beef it up to get the best Horses out of it.

Leo

[raycow]

Ok, just to make sure we are all on the same page here, I am talking about opening the throttle SLOWLY, not stomping it to the floor all at once. Can you do this without the engine dying? And of course I mean do it in drive, so there is a load on the engine.

If not, then put the transmlssion in 1 or L (I can't remember what a TH350 shift quadrant looks like) and take the car up to about 30 mph. Then, once again, push the throttle to the floor slowly, but you have to get it fully open before the engine runs out of revs. If the engine winds up too rapidly in L, shift to 2 and try it from about 50 mph this time - but remember, SLOWLY.

Basically, I am trying to find out if your accelerator pump isn't working, or your secondaries are opening too quickly, or if you are just plain running out of fuel. If the engine won't accept full throttle at any safe rpm, then the carb could very well be too big for the engine.

Even though you think you are flooding the engine, you aren't. What you actually have is a lean condition. You aren't getting enough air velocity through the carb (at full throttle) to pull fuel out of the bowl. Since you said you had the same problem with another carb, I think it is unlikely that you got two defective carbs in a row.

Ray

[ljrsports]

Ray, I have the original intake and 2 barrel carb back on the engine which I never have any issue like I had with the 4's so I'm sorry to say I can't do any of the tests you recommend. I was able to answer the earlier questions from memory. I guess what I need to know is, with the flat top pistons and the comp cam, what is your best advice as far as intake and carb size.


Thanks
Leo

[raycow]

Well, I'm sorry you can't run the tests just now, but I can certainly understand putting the 2 barrel back on so you can drive the car.

The calculation for carb size is fairly simple. Assuming 100% volumetric efficiency, which you won't get in real life, a 350 cube engine at 5000 rpm (I just picked that speed out of the air) will need about 506 cfm. Adjusting for VE will lower that figure, not raise it.

Here is an online calculator if you want to play around with the numbers. That's the first hit I got on Google. There are plenty of others. http://www.gtsparkplugs.com/CarbCFMCalc.html

Now I know you will say that people run larger carbs than that every day - and they do. The trick to this is to not allow everything to open up all at once. A carb intended to be driven on the street will have vacuum-operated secondaries which open slowly as the revs go up and the engine can use the additional air.

Ray

[ljrsports]

Ray, Thank You for all your advice. I think I'll go with the T/A Stage 1 Intake and maybe a Demon 600 cfm Carb and if I need to get more air flow threw that set up, I'll have to figure that out at that time. Thanks again Leo

[bob k. mando]

Here is an online calculator if you want to play around with the numbers. That's the first hit I got on Google. There are plenty of others. http://www.gtsparkplugs.com/CarbCFMCalc.html


bad cow. bad, bad moo cow.



we've got a CFM calculator right here along with a quick reference sheet.

http://www.teambuick.com/forums/view...cfm_calculator

it should be noted that Buicks seem to like big carbs, when set up right.