For those with decent sized roller cammed small blocks, what are you running your base timing at?

For reference, my cam is a hydraulic roller with 234/238 @ .050 on a 108 LSA in a 10.3 to 1 383. It has 1.6 rockers on I/E.

I'm having a situation where I cannot get my 750HP carb to idle without fouling plugs. Right now the motor has around 21* of timing at the 1150ish RPM idle, and no amount of carb tuning can get it to idle clean. Turning in the idle mixture screws enough to clean it out ends up with the car not restarting without pumping the gas, and surging during light acceleration.

Fattening up the idle mixture enough to get it to restart *better*, ends up with fouled plugs and poor drivability in town from being overly rich. WOT action is great, as even from a sub 1000 RPM idle I can pin the car with no hesitation at all.

The carb just came back from a very reputable shop, and he walked me through all the common problems to check for. All was well. The carb has holes drilled in the primary throttle blades, and it also has the secondary throttle plates easily adjustable from the top. That said, I can get a ton of idle air without uncovering too much of the transfer slots.

I dont really want to lock out my distributor on a street car, as I dont feel that should be necessary. The only problem is that my distributor doesnt have a vacuum advance, but none of my others did either with bigger cams than the one I have now. Any bits of advice? Specs can be provided if needed. This problem has kept me from going to the track for the last three weekends.

TIA for any thoughts.

 

You are gonna need a vac. adv. dist. to be able to get it to run right.

I have one from an 86 Z28. It's from a Canadian car which were factory equipped with vac. adv. dist. Shoot me a PM if you want it. I am on vacation for 2 weeks starting monday so we have to do this quick if you want it.

 

Yes...if it had a quadra-junk installed on it before it came with a computer controlled timing system...in order to switch to a manual carb from the q-junk you must have vacuum advance or you will be throwings rods and pistons and crap around. Good luck...I did it on my 86 z28 and it was worth it.