69 Z28 Timing

[Denis]

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-------Where do you 69 Z guys like to set your timing??? Car Im finishing up is bone stock in all ways.......Bill S

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Disconnect vacuum advance and rev the engine until the centrifugal advance is pegged out (i.e. with Macneish distributor, should be all in by 2500-2800 rpm). Adjust for 36 degrees total. Don't worry about initial timing setting. Reconnect vacuum advance. If road testing causes knocking, retard the timing in 2-degree increments until knock stops.

[olredalert]

-----Thank you, one and all!!!!!!! Its been so long since I had it done that I had forgotten (just another senior moment).........Bill S

[Chevy454]

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Where do you 69 Z guys like to set your timing???

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From a technical stand point, your timing is determined by a few things, namely cylinder pressure & fuel...timing up to the point of detonation is not always the optimum point...most folks would be surprised at how *low* some engines like their total timing to achieve optimum HP.

[Plowman]

Vacuum advaance should be no more than 10 degrees. Paul

[L78steve]

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Vacuum advaance should be no more than 10 degrees. Paul

[/ QUOTE ]I'm not saying you are wrong but how did you come up with the 10 deg.figure for a max ?

[Plowman]

Got it from school

[Plowman]

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Vacuum advaance should be no more than 10 degrees. Paul

[/ QUOTE ]I'm not saying you are wrong but how did you come up with the 10 deg.figure for a max ?

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I learned it at school 40 years ago, but I have found it to be true throughout the years.

Some vacuum advance units pull 20 degrees. You have to check it out with a timing light. Each engine has varying vacuum at idle depending on the engine, cam shaft, etc. 10 degrees is what I found to be a good idle. Any more than that and you get really rough idle from over timing. 10 degrees of VA at idle means you can adjust the idle mixture screws to run idle leaner so you don’t load up or get puddling of fuel at idle.

VA for street use is for fuel economy. So, as you hit the accelerator you lose vacuum. When you are off the accelerator you have vacuum advance.

[Gary L]

I have a stock built 302. The mech advance is 18* and the initial is 18* all in by 2800 RPM. I also have 15* of full vacuum advance. This is on 92 octane. The 30-30 cam needs alot of timing to run best. I also have the primary jets at #72 with headers. Plowman is correct. I have a Crane cam that limits the vacuum advance. Full vacuum advance allows leam mixtures (at idle and cruise) time to ignite and lets the engine run cooler.

[L78steve]

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Vacuum advance should be no more than 10 degrees. Paul

[/ QUOTE ]I'm not saying you are wrong but how did you come up with the 10 deg.figure for a max ?

[/ QUOTE ]I've been experimenting with timing and I too found that the 18/18/10 works the best .At first I used the 355 can that gives 15 degrees and the drivability at low speed was horrible .Tried a 10 degree can and all was good .All vac. advance in at 8 inches of Hg .

[396L35]

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-------Where do you 69 Z guys like to set your timing??? Car Im finishing up is bone stock in all ways.......Bill S

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Disconnect vacuum advance and rev the engine until the centrifugal advance is pegged out (i.e. with Macneish distributor, should be all in by 2500-2800 rpm). Adjust for 36 degrees total. Don't worry about initial timing setting. Reconnect vacuum advance. If road testing causes knocking, retard the timing in 2-degree increments until knock stops.

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Thats how I set my Z28 up and it purrs like a kitten, pulls hard up to 7000-7500 range on regular pump gas no additives. Good luck and have fun Bill. Mark