Auto Racing: too much carburation?, mallory unilite, air jets

Question
I have a 61 Corvette with a 350 chevy with 8.5 to 1 compression.  I have performer rpm heads,headers,mallory unilite dist with a blaster coil,comp thumper flat tappet cam.This is a 4speed car.  I am running 2-500cfm carbs.  The car runs pretty good at cruisin speed and a wot but loads up at idle.  Do you think I have too much carb. I'm thinking about changing to a single four but sure like the looks of the 2 4's...Thanks for any help...Bruce

Answer
Hi Bruce

You don't tell me the lift and duration on your cam which would be a little help. But never mind that.

Most serious V-8 race cars are limited by rules to a single four barrel carb, and most of them use 750's .  Of course they also have camshafts that idle at 1800 RPM and take the motor to 83-8400 at WOT.

You need to check your plugs after a relatively long run, a hot lap or two at the local road race circuit would help. If you must, use a safe straight part of an Interstate, stay in third and run at maybe 90 MPH.  The drag strip is useless for this.  At the end of the longest straightaway, lift and shut the motor down at the same INSTANT, coast to a stop and pull the plugs. They should have a very light coating of milk chocolate colored stuff on the insulators, Look DEEP into the plug though, the stuff on the surface doesn't mean much. If it's dark or black, the arrangement is too rich, you must re-jet them to something smaller both fuel and air jets should be changed, maintaining the air size at about 130% of the fuel jet size.

Once you get the high speed mixture right, then you will have to reduce the size of your idle jets to get that mixture correct.  While you're at it, make sure your throttle plates are fully closed at idle. If the car won't idle, increase the size of your idle AIR jets first and then add larger idle fuel jets.

Now it may be that the two 500's are simply too much for your motor and cam. It's easy to over-carburate an engine for street use.  And it's hard to run highly modified motors on the street with any success.  In a case like that , there's a lot to be siad for turbos. Yeah, they're expensive, but you can run an 8.8:1 motor with one carb and make an easy 500 HP on a stock camshaft.

Good luck to you- - -and I would really like to hear about your results.

Thanks

Dan Liddy
Sarasota Florida