After getting my stock distributor rebuilt by Lars (thanks again Lars) and reading his install/timing instructions, I see it should be set at 12 degrees, but I was sure that my manual said 8 degrees. Anyway, since I cannot tell by listening whether I am pinging or not, I guess knowing 8 or 12 would help me if someone knows. This would be at idle, vacuum advance unhooked and plugged (to the carb). thanks, I am just not sure..

 

8* is the setting according to the service manuals, and it will work, but it is based on getting lowest emissions best mileage mix. 12* is more optimized for a performance type tune, with an expectation to have all the timing in in the right RPM range in general terms. it also depends on the motor and all its particulars. Set it a 12 to start and if you have a dial back timing light you can tweak it form there

 

If Lars set it up to run 12 degrees initial that is what you should set your timing at. Optimum timing occurs at 34 ~36 full mechanical advance including the idle setting. That is probably what Lars set your distributor for. So if you set your initial timing to 8 degrees your max will probably be in the 30 ~ 32 degree range which is too low for optimum performance. Go with what Lars said.

 

Disconnect and plug the vaccum advance. Use a dialback light and set the timimg so that it is at 36* at 2500-3000 rpm (wherever the mechanical advance stops). Then reconnect the vacuum advance (ported vacuum for emissions, manifold vacuum for a slightly smoother idle). This should give you the best performance

After all, how often do you drive at idle?

 

 

All my engines never ran good on 8, I had to use 12 to get them to idle good, but they were tuned with a higher CR (10/1)

 

the only thing he could change is the vac. advance can. other than that your timing is up to you. not some dude who rebuilt it in 10 mins

 

What?

He can set the timing curve and how much or little centrifical advance. If you are talking about Lars being the dude that set it up in 10 minutes you are sadly mistaken.

 

I say "Amen" to Gordonm's statement.

Ralph.

 

Many performance distributors are set up to run with 12 degrees of initial lead as the distributor has 24. Simple math 12 + 24 = 36. If you were told to run it there, do so. A engine runs crisp and cleaner with more lead. Usually a good grade of fuel will also help.

 

Quote:
Originally Posted by rebc3
the only thing he could change is the vac. advance can. other than that your timing is up to you. not some dude who rebuilt it in 10 mins

What?

He can set the timing curve and how much or little centrifical advance. If you are talking about Lars being the dude that set it up in 10 minutes you are sadly mistaken.



Yo, what's up with that rebc dude....go away...........

 

OLD SKOOL inch it up until it pings under load and then back off 2 degrees

 

Rookie.
For real. Lars does great work and takes much more than 10 minutes to set up the distro. Heck, it takes 10 minutes to get through the first beer.

 

OK, put down the moonshine and pay attention, you might learn something. I'll talk slow so you can keep up.

There are two curves in the distributor that can be adjusted. The first is the centrifugal advance. This amount of advance can be altered by the length of the limiting slot or by the size of the limiter bushing that's installed on the pin. The slot can be made shorter by brazing it or a larger bushing can be put on the pin to accomplish the same thing. For a performance curve the advance is adjusted so that at idle the timing is 12 degrees with the slot allowing an additional 24 degrees of advance giving a total of 36 degrees at wide open throttle. At wide open throttle there is no vacuum in the engine so the 36 degrees is not effected by the vacuum canister. The other adjustment that can be made to the centrifugal advance is the speed at which the distributor advances the timing. This is done by changing to lighter or heavier springs which causes the advance to come in faster or slower. A heavier spring will cause the advance to come fully in slower and at a higher rpm. A lighter spring will cause the advance to come in sooner and at a lower rpm.

The other adjustment to the distributor that can be made is the amount of advance controlled by the vacuum canister. GM has many different vacuum canisters but the one that works best with a performance curve allows approximately 10 degrees of advance. This advance supplements the centrifugal advance at low engine speeds during high vacuum. As the engine speeds up and vacuum drops the cannister has less effect until zero vacuum is reached which then allows no effect due to no vacuum. Adjustable vacuum cannisters do not work because they routinely allow only adjustment to the speed at which advance occurs, not the amount of advance. So stay away from adjustable units. Lars has a spec sheet in the Tech Tips sections that gives part numbers for the various vacuum cannisters.

A well set up distributor curve will allow maximum advance throughout the rpm range without pinging.

Let me know if I went too fast for you.

 

I have found some non-performance distibutors allow 28 degrees of mechanical advance.