Hi All I have finally got my hot rod back on the road wit mew paint,interior & engine. the problems ive got are:- Its very hard to start when its cold (starts first time after that). It pings at full throttle. If i hook the vacuum advance up it wont idle below 1000rpm. It runs on some times. The engine is a 350 chevy bored 30 thou with mildly domed SpeedPro pistons, 76cc heads with stainless valves & single layer metal head gasket. (should be 10.1 max) The cam is a Howards #112031 .480 in & ex 288 duration & 108 lobe seperation. Induction is a edelbrock c26 with two 600 edelbrock carbs. Spark is a new Mallory Unilite set at 8 deg static with 34 total (i have also tried it at 12 static) Ive tried lots of things I:E another dizzy, had the carbs to bits twice etc etc Any ideas ?
Did you degree the cam ? What octane is your fuel, funny that it would ping at high rpm with 8 degrees and 34 total ? Did you set timing with vacuum line off ?
Thanks for the reply the cam was set up on standard marks (as per the instuctions) but not degreed, the fuel here is 95 octane & yep timing set with vacuum advance off ....do you think it would pay to put a dial gauge on the cam and check if its ok ?
I'm wondering about that compression ratio. The combo of slightly domed pistons and a thin head gasket may be taking you higher than you think. I would try some octane booster and see if the problem with pinging goes away. But even at that, 10 to 1 can be touchy with today's gas. Don
Thanks Don I will try some 98 octane or maybe some avgas which is 100 octane & see if the pinging goes away Cheers Preston
I was going to say octane, as well. but if that doesn't do the trick, you might want to look for vacuum leaks, or check the damper to see if TDC is is the right spot. It might have shifted on the rubber, common on older Chevys. Or....there were some Chevys in the 80's that had the timing mark in a different location.
To get a baseline,take a compression test. Hold the throttle open and crank.this should be done with a known good gauge and the engine warm. Now things get interesting. There are many theroies and reasons for running and dynamic compression in engine building and volumes of books have been written on the subject. In general,180-190 psi is limit for pump gas. Yes there are examples of people who can tune higher cr on the street but a good tuner with racing experience is a must. If you fall in this range or lower,simple timing curves and jetting will get you where you want. Lets start here and post some results so we can help you out.
1. Verify TDC with piston stop test - 2 . Compression test ( you'll want to see about 170-180 if you think you are at 10:1) 3. Read this thread http://www.jalopyjournal.com/forum/showthread.php?t=750900 The engine run on, no idle below 1000 Rpms, and ping are all timing related issues. Without the piston stop test your light may be telling you stories.
Please list the piston part numbers and the cylinder head casting numbers. When you put the motor together, did you take "squish" into consideration or not? Did you actually measure and figure the static compression ratio?
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