setting initial timing with manifold vacuum [Archive] - Team Camaro Tech

: setting initial timing with manifold vacuum

May 7th, 03, 09:03 AM

when setting initial timing, i always plug the vac advance canister, but should i also plug the manifold vacuum port on the intake? if i dont, will i still be able to set timing correctly?

also, the weights control how much advance, the springs when it comes in, right?

some say that i should run the lightest springs possible.

the lighter the springs, the later the advance comes in, right?

so would advance that comes in later (3000+) be better for performance than advance that is all in by 2700-3000?

thanks guys

May 7th, 03, 10:07 PM
The lighter the spring the faster the advance and I think you want all your advance in by 2700-3000 rpm.

May 8th, 03, 06:38 AM
Jeff - Plug the source of the vacuum (at the manifold or carb) or you have a vacuum leak and will get bad readings... Springs control how fast or slow your timing comes on...

May 8th, 03, 07:23 AM
thanks guys,


ive since learn that i had this bass ackwards... the lighter the springs, the sooner timing comes on.

and i realize that i dont want the timing coming on too soon cause if im idling at 1000 and my advance comes on at 900 cause of light springs, then my mark will bounce around like a grasshopper ...ring a bell ? smile.gif smile.gif

when we put those heavier springs on there, that was to keep the advance from coming on at the 1200 that the car was idling at.

Since then, we got the car to idle at 800. and the timing is steady as a rock.

So once i get my split mono leafs, konis, poly bushings and cal tracs on (this weekend), i figured id play with the springs a little.

The instructions on that adjustable canister said to run the lightest spring combo possible without pinging and without the timing coming on too soon.

but what im trying to figure out is if a car whose advance is all in sooner (ie 2700 rpm) will perform better than an equal car that has advance all in at 3000.

i know that spring force is linear and that because a lighter spring bring advance on sooner (off idle), the lighter spring will also make total advance come in sooner.

im thinking that i should make all the advance come in as soon as i can (2700 or sooner) rather than later (3000) think of drag cars that lock out their timing... its all in at idle, right?

But if all that is true, is it better to run a little more advance and have it all in later or run a little less advance and have it all in sooner?

ie: more initial/mechanical and heavier springs or less initial/mechanical and lighter springs...

quantity vs rate...


Z28 Mark
May 8th, 03, 05:22 PM
WOW Jeff…. Do you have a PhD or something?
P.S. Your parts are finished being blasted….
Mark (A.K.A. Z28 Mark) or “180* OUT”

May 9th, 03, 05:26 AM
hey mark,

i dont have a Ph D yet, but my dad has a few and my grandpa had a couple.

i guess they are a handy thing to have, but i dont understand why people spend so much time getting one...

whenever my family needed a PhD, we just went to the hardware store and got one in about 10 minutes...

a good Post Hole Digger runs about 50 bucks smile.gif

thanks for the parts buddy!