The Stovebolt Site Forums The Shop Area Engine Shop 235 tune up

i been tuning my 235 in my 58 biscayne ,, i am real close , i am doing it by vacuum i have almost 20 on the gauge , i have the idle close to what i think and timing also , by the highest vacuum , but i still have a little popping in exhaust , just a little ,, whats the best way to adjust the carb , i have been screwing it in until it starts to mis and back it out a little ???

any input would be grateful
thanks

Presumably, you are using the mixture screw to adjust the carburetor (not the idle screw).

I turn the mixture screw in until the engine runs roughly/slower. Then, I turn out the screw until it reaches maximum vacuum.

I'm sure others will chime in, but I don't think 'popping' from the exhaust sounds like carb issues. Have you done a compression and/or leak down test?

Like I said, I'm sure others will have an opinion..

i am on a fresh rebuild , i have did the timing again doing it to get the highest vacuum , it starts great and when given gas it takes it well with no hesitation , the popping is very slight but enough to know its there , the head was redone also and valves
thanks

This is a hydraulic lifter engine, right? If not, how did you adjust the valve lash?

Also, is the carburetor recently rebuilt? The float adjustment might be a little off.

no carb work at all ,, yes hyd lifters ,, i did by adjusting them until0 lash and i give them 1 turn more

thanks

I'll bet your valves are too tight. I had the same problem on my truck. Ran good but popping noise from tailpipes, also was down on power. I found that you need to get engine to normal operating temp and THEN adjust the valves, solved my problem.
Good luck!
Darren

ok i might have to try that ,, i need to let weather warm up a tad bit ,, what is your oct setting on ( 1/2 nut at bottom of dizzy )

thanks

You set the octane selector to zero before adjusting the timing. The octane selector was useful when you bought different grades of gasoline and/or you were driving at different altitudes. You could fiddle with the octane selector and later set it back to 0 when you got home.

Great thanks