I have a good question for you tech heads with big cam strokers. I have been working on my engine tune for a while and just aggrivated at it!! My question is this this my 347 has a roller cam thats about 256@.50 11.0 comp. with a victor intake and its really cold natured is this baceuse of the lack of vaccume? Or poor tune?
Have you adjusted the idle mixture screws properly (i.e. with a vacuum gauge)? If not, proper adjustment can make all the difference in the world with cold idle quality. My last motor had a 272/276 @ .050 in it and I just had to keep the RPM up for a few seconds before it would idle on its own. When stone cold it would only idle on its own at about 800 but would not die either.
I think your problem is a little of both......for every increase in performance you have to sacrifice economy and vise-a-versa....
I havent used a vaccume guage on it yet. i will have to drill and tap a spacer plate first but, the mixture screws are very sensative 1/2 turn either way and it wont idle in gear at all. But i did win the drag for toys brakette race at my local track this weekend!!
That single plane intake is the problem you have with warmup and low speed operation. You should use a dual plane intake like the performer that has faster airflow rates as well as heats faster. It will provde you with more torque as well. The single plane is a race intake meant for the upper rpm ranges.. We use one on a 351w race motor and it's cold blooded until the coolant temp get up to abut 150. The single plane runners sit above the lifter cover and never get much heat. Now maybe I am misunderstanding your problem but this is the differences with the use of these two intake designs.
sounds possible but with a smaller cam it worked fine but,that was a different combination. I suppose i will just have to live with it if thats the case,i cant use anymore torque and my rpm range is out of site for a dual plane.
Are you sure that it does not have a vacuum leak somewhere? maybe your ignition isnt hot enough to fire the compression you gained from the stroker,,,, How many miles/hours does the engine have on it? if its still fresh, you may be fighting the cyl pressures, all 8 pistons not fully seated in, and causing cyl pressure fluctuations, or if you have not retorqued all the bolts down again, that warm up and cool down can create vacuum leaks very quick from the start and run erratic. Id run a compression test, make sure all the cyl pressures are close to each other, retorque all the intake bolts again, carb mounts and hoses for vacuum. When engines dont seal, they dont idle, they will run high rpm because the vacuum pressures drop and they even out the pressure and run,, To me, it sounds like a vacuum leak, vaccum pressure is highest at idle so if its sucking air in somewhere and idling erraticly, starts hard,,, runs rough, thats where I start to look,,,, JMHO,,, or 2 cents worth,,, Chad
I have a solid tappet cam slightly larger than yours and run a weiand accelerator manifold (single plane) with a demon 650 (no choke) I can blip the accelerator pump (no hood yet) reach in the window and fire it up first thing in the morning no problem. After about 30 seconds (end of the street) it runs very well. I agree with the mixture post above.
Actually, there's not enough info to make a diagnosis. Sounds like a mixture tuning problem but we don't know what carburetor you have. Please list the engine's components, jetting, and timing.
