Does a vacuum leak affect timing?
Does a vacuum leak affect timing?
YES,……. if you have a vacuum advance, and / or retard timing, air leaks can effect the spark timing. some leaks more so than others, the closer the leak is to the sensor (distributor vacuum can) the more effect it will have on timing.
What should the ignition timing be on a 454?
So basically the initial timing of your 454 will depend alot on how much mechanical timing your particular distributor adds. I would shoot for something like what I have – about 10 initial and 22-24 mechanical for a total around 32-34 degrees. Also limit your vacuum advance to about 10 or 12 degrees and you’ll be one happy 454 owner!
What’s the correct timing for a vacuum advance?
Make sure the vacuum advance connection is removed, and now rev the engine up to around 2,500 to 2,800 rpm. Ideally, the timing now should be somewhere around 34 to 36 degrees to total advance. With 34 degrees of total mechanical advance and 14 degrees initial timing, you have 20 degrees of mechanical advance—14 + 20 = 34.
What should timing mark be on FMCA 454?
The hard part is to get a good look at the timing mark bracket mounted on the timing chain cover because of the shroud! The setting should be 4deg. before TDC. Forgot to mention that one needs to remove the Vacuum line going to the vacuum advance on the distributor or the timing will not set correctly.
What causes detonation on a Chevy 454?
Anything past about 34 degrees total timing results in detonation under heavy load, even on 98 octane unleaded fuel. This occurs with or without the vacuum advance connected so I know its a result of initial timing plus mechanical advance.
What are the timing instructions on a Chevy 454?
Chevy 454 Timing Instructions. The numbers to the left of the V, looking at the engine from the front, are degrees of advance or how many degrees before top dead center. The numbers to the right of the V are degrees after top dead center. You always want to have the timing advanced or before top dead center.
The hard part is to get a good look at the timing mark bracket mounted on the timing chain cover because of the shroud! The setting should be 4deg. before TDC. Forgot to mention that one needs to remove the Vacuum line going to the vacuum advance on the distributor or the timing will not set correctly.
What should the timing be on a vacuum advance?
The vacuum advance is now set for 10 degrees of advance at normal highway operating conditions. Remove the vacuum pump and timing light. Reconnect the vacuum-advance hose to the carburetor. A fender cover or old blanket will protect the finish of your car when working under the hood.
Do you need to run vacuum advance at idle?
Vacuum advance tuning is very combination-specific. If that big block is a low compression engine, you’ll probably want to run vacuum advance. Low cylinder pressure engines typically like lots of advance at idle and light throttle to make them responsive.
