383 Build Won't Idle And Run Correctly

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
last summer I had a 383 long block made for me. yes its stroked .030, clearenced pistons for yhe valves, 202 aluminum heads 64cc chambers, roller rockers and normal timing on the chain currently set at 6 degrees with a comp cam 12*210*2 and its all hooked up to a stock and brand new th350 with a stock converter. dont think I missed anything. summit 750 carb electronic ignition. highest octane I can find. other then the timing and other minor things I have yet to adjust anything ( carb idle adjust only). I cant get it to idle properly and still run when its in any gear for some reason. I checked for vaccum leaks and found nothing obvoius. I can only get it to not die at a higher rpm like 1200 but then it just slams into gear and Im sure it will tear up my clutchs. since this is a new build and first stroker I dont want to go fiddling with things till I at least try to find other problems I might have missed. thanks for help.


obviously you'll need to check your ignition advance curve and carb tuning,
check fuel delivery system, volume and pressure, at the carb inlet port, verify the engines
ignition timing, and advance curve, verify you're firing order, and check for vacuum leaks ,
and make sure you properly dialed in the cam,
and not simply use the dot-to-dot timing set install

if after you verify timing and carb settings jetting, power valves accelerator cam, and properly adjust the valves,
and the car still runs badly,

Id say from the symptoms you list, chances are very good your running a stock stall speed torque converter, and its not going to run correctly with that cam.
simply swapping to a 2500rpm stall converter will solve the issue


just as a bit of info
Ive frequently recommended a crane 114132 flat tap hydraulic cam as a good upgrade in a 10:1 compression, 383 TPI corvette engine build, if you want a fairly inexpensive power upgrade in a 1985-1986 corvette,
and like clock work someone will ask why not a step up to the crane 114142?
the answer is that the stock stall converter, and power brakes work just fine with the 114132 but are marginal at best and act like you describe with the larger duration cam, its just a bit too large in duration to work well with the OEM converter speed.
https://www.summitracing.com/parts/crn-114142?utm_source=bing&utm_medium=cpc&utm_term=+crane++114142&utm_content=Crane+Cams&utm_campaign=Part+Number+Ad+Groups

with that cam, the engine should easily idle at less than 900-1000 rpm
but even then it will provide a noticeable jolt as the auto trans,
is put into gear and you'll need to keep your foot on the brake,
to keep the car from constantly crawling forward in gear if the stock stall converters used
 
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