I was wondering what you guys set your ignition tmiing too, i'll be tuning my friends car ('79 z)for him tomarrow, this is wha he's got:

79 350, dart s/r's (reworked), performer intake (not RPM-ported/polished, 600 CFM holly (single feed), crane blueracer cam (.490I, 510E), 1.5 rockers.
i have the total advance at about 28-30 degrees

was also wondering what jet's he should be using..i have 67's in there now...any other advice or tips?...thanks

Tony

 

Well, I dont know if this helps, but I have a 79 Z28, 350 with all the usual goodies for the street. My timing is set but I have no idea what it is set to. My timing line points right up to my hood but it runs perfectly fine. You may adjust the timing to where your burn sounds even coming through the exaust, then drive it and see if its nudging (too fast) or slacking. Also, as with all hp goodies, if your timing is to slow it may make the motor run a little hot. Hope this helps. Good luck!

 

First off, let me say that these numbers will get you in the "ball park",
but don't take them as written in stone for your motor. Each engine
is going to require different timing and advance curves.

The motor will let you know what timing it likes best, but off hand
I would imagine your total timing is a little low.

The best method to set timing is to use a dyno of course; even
a 1/4 mile test will get you the best MPH for the optimal timing.

My base timing is set to 23 degress @ 1200 RPM (before mechanical kicks in).

I have no vacuum advance.

My total is 37 degrees.

Click the "POST YOUR SMALL BLOCK COMBO" link to see all my mods.

 

By "total" advance I assume you mean initial plus maximum centrifugal advance. If so, you'll want to shoot for about 34-36* total advance for best power on a typical natrully aspirated small block Chevy. Shoot for the right total advance number and let the initial advance fall where it may. If you've got, say 20* of centrifugal advance and go for 34* totoal advance you will end up at about 14* intial advance (34 - 20 = 14* initial)

Deal with vacuum advance AFTER you get the initial, centrifugal and total advance worked out. Usually you will find that a stock vacuum advance canister supplies FAR too much advance. you'll be getting significant part throttle detonation once you have the total timing set for best power. I highly recommend a Crane adjustable vacuum advance canister (if you are using an HEI distributor, common to these cars in stock form). It is adjustable for both rate of advance as well as maximum centrifugal advance. A good starting point would be to use the supplied advance limiting cam to lock out as much vacuum advance as possible. This will leave you with about 12* of vacuum advance- which is a good starting point for a performance-oriented motor (stock cans usually supply about twice that- which is way way too much for a typical performance application).

 

Damon,

Not sure if you're referring to my post, but yes...by total I mean
wide open throttle, mechanical advance plus base timing.

That's the recommended method to set timing as you mentioned.
Total timing is where it's at...unless you know how much mechanical advance (and vacuum advance if applicable) the
distributor will provide, you must use total advance to set timing.

 

No, just repying to the original post. I think we're in what I like to call "violent agreement."