Okay, so i got my engine back and I am trying to tune it. I have two questions.

I have a question about how to set initial timing and how much is too much. I use the advance and retard method using a vacuum guage. It produces the most vaccuum at 24 degrees advance at idle in nuetral according to the timing light. Is this too much? It doesnt seem to ping under hard accelleration. how obvious would a ping be?

My other question is about the vacuume advance. at tidle I iave no vaccume at the vacuum port on the carb. the hose is not blocked becase I blew into it and the arit flowed through it. is this normal or is something wrong?

 

You won't get any vacuum at a ported source until you open the throttle because it is above the throttle plate. Initial timing requirementvaries with the dist curve, but stock 6-10 degrees on the crank should be plenty. Years ago when drag racing the engines idled so high some guys just locked the weights and ran the total lead on the crank. In that situation 32 degrees would probably be close for a small block.

 

You should not set timing with a vacuum gauge. Tuning the carb with a vacuum gauge is great, but setting timing with one will give you waaaaaaay too much advance, because the engine runs better under no load with LOTS of advance.

If you have a stock cam, 8-10* of advance at idle with the vacuum advance hose disconnected and plugged should be about right. Basically as high as you can get it without getting pinging while climbing a steep hill in high gear while lightly accelerating. If you've swapped to a more aggressive cam, you may need up to 14* of advance at idle depending on the grind (the manufacturer's tech line will tell you the proper advance curve).

As 67 coupe said, there should be no vacuum at the ported vacuum port on the carb at idle. The idea is that you get extra advance only when you're cruising at part throttle for better economy.

In addition to setting the static timing (at idle), it's a good idea to check the dynamic timing as well. Once you've got the static timing set, rev the engine to 2500, 2800, and 3000 rpm and check the advance at each point. Most sbf's like 28-32* of total advance by ~2800 rpm. It's common for original distributors to have worn out springs and bushings that will alter this timing curve and reduce performance.

 

i've always heard 36 total and about 12 idle is best