I have a question about timing here. searched and didn;t quite find a good source.

I will be running nearly 10-1(maybe 9.9)CR on a NA 350. Iron heads.

The shop seems to want me to get an adjustable vacuum can, and run full timing like stock but limited. so 6 at idle and what not.

I've heard of so many other ways to get better responce by locking it out, limiting timing travel.

In my situation, i have access to 93 octane all day long.

What timing would anyone here recomend for a street strip car, mostly driven around town, but i want it to kick but when i want it to.

 

On a street car? Don't lock out any timing.

 

ok, i've heard of raising the base timing, and just limiting the mount of timing that can be added.

How does this sound?

More advance at idle is a good thing right? but at higher rpm, with stock mechanical advance, if your idle was at say 18 idle, high rpm would be another 10, so in eccense, too much.

 

The car wants to have around 34 degrees of timing all in by about 2500 RPM. Change the weights and springs until the timing is all in by then, and set the timing to 34 degrees and don't worry much about what it is at idle. If it knocks at WOT, you can take a couple degrees out. If it doesn't, you can maybe add a couple degrees until just before it does.

 

ok so more timing at adle isn't a good thing?

what about the whole vacuum advance thing. I'd love to be able to remove that sucker, what benefit if any will i achieve by remove it entirely?

I dont see the need for it, if the 34* is aquired by 2500rpm.

thanks so far...

 

Removing the vacuum timing on the street is an excellent idea if your mileage is too good and your plugs last too long.

Get an adjustable can and set it up the way the car likes. It will probably be less than 16 degrees at 10 or 12 inHg.

 

i noticed that at low rpms under load (like cruisin' up the highway) with the vacuum advance hooked up, i'd run into detonation issues. took the vacuum advance off and the detonation went away. i'm running 18* initial timing at idle with 36* total by 2500rpms.

what is the cam you'll be running?

 

On a stock advance can?

 

cam is a custom grind from comp,

.520/.544, 234/244 duration @.050, 114lsa

kinda large, but it needed it. lots of duration! lots of overlap!

 

i think so, are you talking about the vacuum advance can on the side of the dizzy? if so, yes, it's stock for a 1979 chevy monza with a 305. but i have some lightweight springs in it now.
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i've got a little more duration with 238*/248* @.050 and i was told by f-bird '88 to run 18* initial timing, and the car picked up enormously off the line. it also helps keep the motor from loading up with fuel (carbed car)

 

Some stock vacuum advance cans have something like 20 or 24 degrees in them, it's way too much when you've got the mechanical advance set up to come in faster.

 

oh, yeah, i know that. it had something like 54* total timing or something retarded like that, which is why i took it off. my car runs great though without it, still knocks down 16mpg in town and 21+highway. i'm stoked about it...oh yeah, and should run 11.8's once i get it all squared around at the track (rearend stuff, not motor related)

 

Is the car street driven?

before i was having problems with it loading up with fuel as well, the longer it idled, the worse things got.

18* doesn't seem like it would cause much of a problem with the starter either. would it?

 

i drive it everyday, it's my only car! i never have problems with the starter due to too much initial timing...

 

18* initial, with what setup?

how much total timing?

you said you had the vacuum taken off right?

 

he said 36* total so hes running 18* of mech. advance and 18* initial, no vacuum advance.

 

i'm blind, so the stock mechanical advance gives 18* right?

so the 18* intial, plus the 18* mechnaical, will mean 36* at throttle.

i'll have to try that when the new engine goes in...

 

Unless you change the weights and springs, you won't be getting that 36 degrees until about 5000 RPM, which is a little late.

 

yeah, i have the lightweight springs in mine, and it's all in pretty early...like 2500 rpms or so.