dmfinley posted:i have a 351 with the Yates heads and Ford high rise. Solid flat lifters. I do not know what the cam is. Guy I bought it from had engine built but couldn’t find cam info. Ran about three thousand miles and ran fine. Summit 750 carb. Idled decent and had brakes all the time. Didn’t put a vacuum gauge on it. First mistake. Noticed the other day valve train was pretty noisy. Pulled covers. Lash cold was about .029-.030. Not knowing cam specs did a lot of research and guessed on .022 hot. Everyone said to subtract .006 for cold so .016 it was.
Started up and when warm sounded like the “sewing machine” But the idle was rough and adjusting screws little effect. Bought a vacuum gauge. Idle at 700 is 7 inches! Thought I had a vacuum leak but I checked everything no leaks. Runs great down road but idle quality way worse than before. Can tightening the lash .013-014 make that much difference?
I even pulled the power valves which were 9.5 and put in 3.5. I see no difference. Idle screws still make almost no difference.
What am I missing?
Thanks
David Finley #3659
You might find out that you are going to be cutting out sometimes by using a 3.5 power valve. If you have about seven inches of vacuum at warm idle, it may take too long for the 3.5 power valve to open. It might not happen all of the time and altitude and air temperature could be a factor. Perhaps a 5.5 power valve would work better for you.