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64Joker
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324 Posts
Discussion Starter · #1 ·
I'm interested in just "checking" my timing mark on my 64 Chevy smallblock, do I still need to plug the distributor vacuum hose? I don't plan on adjusting at this time!
 

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Hot Rod Has Been
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I believe it would be "total timing"!?
Check the "static' timing by setting the idle RPM's to specs (about 550 RPM's) then disconnect the vacuum hose from the dizzy.

If you want to check the "total advance" leave the vacuum hose connected and rev the engine to about 3,000 RPM's and either read the timing light gauge OR what's on the timing tape/marks on the balancer (if so equipped).

Check the mechanical advance by disconnecting the vacuum and reving to 3K and reading the light or the timing tape.
 

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WFO
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I'm interested in just "checking" my timing mark on my 64 Chevy smallblock, do I still need to plug the distributor vacuum hose? I don't plan on adjusting at this time!
Disconnect and plug it to check the initial advance (initial advance is the timing at idle). But the initial advance is not all of it- you really need to know what the total timing is (total timing = initial plus mechanical)- or else the engine can be damaged or have poor performance from detonation or insufficient advance at higher RPM.

To check the mechanical advance, use a timing tape or a dial back timing light and accelerate the engine until the mechanical advance quits advancing. The reading there is the total timing. The total timing for most SBC engines should be around 36 degrees, less for Vortec or 'fast burn'-type heads.

If you want to know how much the vacuum advance adds, attach the vacuum line to the vacuum advance and at idle take a reading. Disconnect it and take another reading. The difference between the two is the vacuum advance. Usually you need about 10-12 degrees from the vacuum advance. Stock vacuum advance cans often add more than that.

The combined advance (mechanical plus initial plus vacuum) should fall somewhere around 50 degrees under light throttle cruise conditions (engine vacuum high, throttle setting relatively low).

More on timing here, including how to make a timing tape and how to tell if the timing marks are accurate.
 
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