69 Z28 Timing

[L78steve]

[ QUOTE ]
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

[Steve Shauger]

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If jerry set the distributor up he curved it. There should be a paper that came with it telling where to set the distributor up at idle and where it should be at around 2800 rpm's. probably 12-14 degrees at idle. No vacuum advance is necessary with jerry's set-up.

[/ QUOTE ]

The main function of vacuum advance is during lean conditions, such as highway driving, fuel takes longer to burn, and by starting the burn cycle earlier (via vacuum advance) you get a more complete burn and increase effiency. Its probably a good idea to use on street engines.

[Salvatore]

Hey Steve, You and Paul (both of ya old timers) have a point. I am going to re-asses my set up for the street. Thanks!

[Plowman]

[ QUOTE ]
[ QUOTE ]
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 ?

[/ QUOTE ]

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.

[Salvatore]

I have a buddy that lives in Clovis. He loves the weather. A little nicer than chilly Philly where he is from!

[Gary L]

[ QUOTE ]
I have a buddy that lives in Clovis. He loves the weather. A little nicer than chilly Philly where he is from!

[/ QUOTE ]

Is he into the Camaro/Classic car thing? Does he have a car he takes to shows?

[L78steve]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
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 .

[Salvatore]

[ QUOTE ]
[ QUOTE ]
I have a buddy that lives in Clovis. He loves the weather. A little nicer than chilly Philly where he is from!

[/ QUOTE ]

Is he into the Camaro/Classic car thing? Does he have a car he takes to shows?

[/ QUOTE ] Nope, Not a car guy. He is from lansdale, Pa. and moved out there after he retired. he loves it there. His kids also live there. Its easy to live on the west coast when you spent 50 years in the east here.