More power out of my 2bbl

Hello, I was wondering if there are any ways to get more power with my stock 2bbl carb on my 302. Its a stock 1972 302 with headers, dual exhaust, electronic ignition and an open element air cleaner. I already removed the plastic limiter caps on the mixture screws, and was going to remove the choke flap but I can't find a socket to fit it. Would there be any benefits of changing jets or different accelerator pump? And any tuning advice would be greatly appreciated.

Thanks,
Jon

 

Tuning Advice.... I Would Recommend A Good 4v Aluminum Intake And 600 Edelbrock Or Holley. The 2bbl's Are Decent Carbs But Not Intended For Performance, But If You Wanna Keep It A 2v Car, You Can Always Find A 2bbl Holley, They Work Pretty Good On A 302. Just My $0.02..

 

yeah I know a 4bbl is the way to go but, I just want to play with my 2bbl for a while because it runs pretty strong as is and its fun showing people my stock intake and carb after I beat them :evilsmile

 

Don't waste your time on a 2-barrel. The only thing you'll accomplish is poor fuel ecconomy. They have great low-end, but run out of "steam" in the mid and upper RPM range...

 

guess I'll just figure it out myself..

 

The stock 2bl is kind of limited to what will improve performance. Flows about 375 cfm if I remember right. Most you could do would be to remove the choke plate, try rejetting for your air density etc. and maybe do some blending and polishing in the air horn. Make sure the throttle plates are open fully and might even check the base gasket match to the throttle plate bores and intake. I think it is a neat idea to run like you say, but the engine is really an air pump and more is better up to the limits of the cam, heads, and compression ratio. Back when I ran them on circle track(60's) only other thing to help HP was to add a pint of Cox model airplane fuel in 5gal of gas. Had a lot of nitro in it, not too legal either. Gambling on keeping the engine intact too. JMO

 

Johnny Rebel,
the problem with your two barrel carb is it's size. It will only flow 300 -350 CFM and your engine needs about 500 cfm in stock form. Going up 2 or 3 jet sizes will give you a richer mixture and will make a little more power but when your engine gets to about 4000 rpm you will be sucking raw gas because you can't pull any more air through the carb. It will go rich, foul plugs, and wash the cylinders with raw fuel wearing your engine at a faster pace than it would with the stock jets. The air horn - even with the choke plate in place will flow more air than the venturis will removing those parts won't increase your performance at all. Cutting the airhorn off (its been done) actually hurts performance so don't do that.
To get the most from your 2bbl do away with the air cleaner snorkel and preheater for the incoming air. Tur the air cleaner top upside down and put it on that way. It will give you a gap all around the filter for an easier path for incoming air. Direct cold air to the cleaner opening from the front of the car. Cold air makes more hp than warm air. Make sure that your throttle is opening up completely - adjust the linkage to make sure it opens without going past wide open throttle. Put a spring kit in the distributor to make it advance as fast as possible, Limit your mechanical advance to 20 degrees by turning the advance plate so that the groove stamped "10L" is where the stop in the distributor is working. Set your timing at 3000 rpm for 32 to 34 degrees total timing with the vaccuum line off the distributor. That will give you about 12 to 14 degrees initial advance. Make sure your vacuum line to the distributor is supplied by the carburetor "timed vacuum port" and not into the manifold vacuum. You can tell the right port because it will not have any vacuum with the throttle closed but when the throttle is opened it will have full manifold vacuum. Run a 180 to 190 degree thermostat and one step colder plugs than stock. Beyond that you can increase your combustion ratio by planing the heads and running "shim" type head gaskets that are thinner than normal. Go to a good electronic ignition distributor and 8mm copper or steel core wires.
That will give you as much as you can get out of a carb that is just too small for the engine it is attached to.

 

There is nothing to figure out. The 2v is not big enough for any mods to really make a difference. I am not sure why you are ignoring the advice that you asked for.

 

Figure what out? You were given the best advice possible. Sheesh...

 

If you want to squeeze the last little bit out of it, you got some good leads from Old Guy.

Grind the choke horn totally off, then blend the remains into the top of the venturis.
Make sure to keep the air cleaner boss.
Get a K&N filter.
'Super tune' the accellerator pump circuit. (Don't ask me how on a Motorcraft! I can do it with my eyes closed on a Holley...)
Check your throttle stop, pedal, and all adjustments between to make sure your throttle plates open all the way when someone pushes the pedal to the floor.
Take your intake off and cover the exhaust crossover passages.
Put a phenolic spacer under the carb to reduce heat.
Use a high flow inline filter somewhere inline with the fuel system... Then take out the low flow factory style filter that screws into the front of the carb.
Wrap/insulate any and all fuel lines in the engine bay.

Don't change any jetting until you need to, although headers, HEI, and any serious modding to the choke horn will surely need more jetting.

When you check the fuel pump diaphram, make sure the carb body has an umbrella type check valve. The BB type is not nearly as responsive. Sometimes you can take the BB out and put the umbrella in, but not always.

All these mods I gave you here, even if done to perfection, would only gain you 10 hp best case. A small 4v, just thrown on without nearly as much care and attention would give you 15 hp easy. 20-25 hp if you did all the extras and super tuned it. However, for streetability, I don't recommend removing the choke and related stuff on a good 4v carb.

Good luck
Dave

Edit: I know you said you have an open air cleaner, however:
A true drop base, Moroso for example, will actually flow more air. The bottom is contoured to drive the air up into the lid of the cleaner. Then the lid is domed to use the velocity to push the air down into the carb. Flat top/bottom air cleaner assemblies are turbulent and therefore restrictive right over the venturis.

 

You can a performance Holley 2-bbl. It's 500 cfm used primarily on circle track racers. Bye-bye fuel economy, though.

 

oops, Sorry I din't mean to be a jerk there

Thanks, theres some really good info in here

Does anybody know what size those bolts are that hold on the choke flap? 3/32 is close but doesnt work.

 

If you pull the top off the carb then you can get down into the venturis better. Use a small round hobby file and remove all the casting flash around the venturis and the boosters. Then polish them up with some emory cloth. Don't try to hog out anything with the file, just polish it. It's not a kick in the pants type of improvement, but 2mph is half a lap at the end of a 25 lap feature race on the dirt track.

Cleaver