Auto Racing: missfire@high rpm, holly carbs, camshaft timing

Question
I have a 302 ci ford w/ 471 lift cam,tunnel ram w/2 450 holly carbs,accell points style distributer.engine starts and idles fine but starts to misfire when i step on the gas.I can only turn the dist. so far because of the tunnel ram intake.What should I do to correct this problem?

Answer
Hey Henry

Geesh- - -I have the same trouble with my Datsun race car- - - I even called a real guru the other day myself.  Here's what I learned.

Your 471 cam is mild, your carbs are a LOT- - -it may be the two 450's are simply too much carburetor for that size engine and that cam. 2 450's equal a 900 CFM set up.  The 358 Sprint Cup motors use 750's I think- - - ONE of them.  Borryw if you can a single carb manifold and try that before proceeding

How much timing (total advance) are you using. With pump gas and about a 10:1 compression ratio (I'm guessing) that could be the trouble too. I doubt it. You should run abaout 32-34 Deg. total advance.

Now , I'd start buy getting rid of the points and condensor. Get some sort of CD ignition, there's plenty of stuff available for the 302 distributors. While you have the distributor out, make sure the shaft bushings are ok, there should be no side play in the shaft, and no more than about .002" of end play. Check the cap for crossfire tracks. Check the rotor too !

If you have questions about which ignition system is right for you , call Summit Racing on their tech line 1-330-630-3030 it's a toll call so use your cell phone. They will help you find what you need for your system.  Once you've decided, they're a good place to buy that stuff too. Big company that really tries to give good serviice.

Next, check your cam timing with the manufacturer's recommendation.  Also , remove the air filters, containters and all, and run the engine at about 4500 RPM for a minute. Hold your hand about 2" over each carb and see if you feel suction or if you feel some pressure against your hand. If you do, you have reversion. Your camshaft timing is a bit too far advanced. This can cause all sorts of strange things to happen. You may also see a very light fog above the carbs, this also indicates reversion.

Finally , if the intake manifold interferes with correct ignition timing , something will have to be done. Ignition timing , CORRECT ignition timing is vital to good engine performance, and wrong timing can cause engine failure. You may have to grind a relief in that pretty manifold.

Good luck, If you find the answer somewhere , please let me know. I keep a library of solutions like this and would like to include yours

Thanks for writing !

Dan Liddy
Sarasota Florida