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Posted: Sun 16 Aug 2009, 08:16
Can anyone of you knowledgable gents advise me on my engine timing? especially at altitude.
350 chevy , HEI Dizzy, what are the specs?
Re: 350 timing
Posted: Sun 16 Aug 2009, 20:20
Timing depends on combination , heads, cam, exhaust.
Somewhere between 12 and 20 static. Total timing better done on dyno , just before detonation/ Best power.
Easiest way. Rev your engine up to 3000RPM. Hold it there, advance your dizzy by hand untill the engine starts shaking, back it off untill engine smooths out, lock it in place.
Re: 350 timing
Posted: Mon 17 Aug 2009, 07:20
Before we start , there are 2 types of advance , vacuum and centrifugal. You are not concerned with vacuum when you set your timing..ONLY centrifugal
The timing should be 36-38 degrees all in by 3000-3500 rpm ... preferably all in by 3000 rpm.
Most distributors have 24 degrees of centrifugal advance so if yours is like that , 12-14 degrees at idle WITHOUT vacuum advance connected is ok.
The real way to do this is use a dial back timing light , disconnect vac advance, rev the engine to a rpm where there is no more centrifugal advance and set it to 36-38 degrees.
Then reconnect vac advance to FULL MANIFOLD (not ported) vacuum. Ported vacuum is an emmisions band aid , do NOT use it.
You can fine tune the car by advancing and testing for detonation by going up a hill in top gear and booting it , once you hear pinging , retard 2 degrees or so till the pinging stops.
NEVER set timing , apart from the hill test , with vacuum advance conected.
Some dizzys have very slow mechanical (centrifugal) advance and often wont be all in till 5000 rpm , this is not what you want for a performance car .. you need to change the springs of the mechanical advance to lighter ones , you might also have too little or too much mechanical advance in the distributor itself and thus have to modify the stops of the weights.
Its not just the amount of advance that is important , its the advance curve that is too , to get best performance.