How have most of you done this? Dremel tool????? I would think that would work best....but how much do I grind out? I don't want to go too much. I figure that the best bet is to try to get 24 degrees of mechanical advance....I am assuming that my stock replacemnet distributor is giving me 20 degrees.

 

You're assuming a lot and, if it is 20degrees, it's just about right.
Don't need to modify it.

Set the timing for 12 to 16 initial and 32 to 36 total at high rpm.
About 3000rpm. (medium distributor springs)
+ an additional 10 to 15 deg vacuum advance during light throttle hiway cruise. This is a good street performance curve.
May be too aggressive if you run crappy gas.

The amount of total advance on an HEI is limited by the shape of the weights, not the slot.

What is the number stamped on the side of the distributor housing? I have some listings, can look it up.

 

Where is it exactly and what #'s do you have listings for? This is a remaned Cardone unit.

The mechanical advance is limited by the shape of the weights? Are you sure? The advance kit I have says that if I use the weights with the lightest springs I'll get 22 degrees.

 

Its a 7 didgit # stamped in the housing right near the cap.
like 1112684.
My listing are for stock GM distributors installed on different stock motors over the years.

A remanufactured distributor may be different.
You don't want the lightest springs, (too unstable at idle and low speed) the weights and center piece are all different on different distributors., giveng different results.
The aftermarket weights and springs are different again and use different weight bushings.

Use their recomendations as a guide only.
A advance timing light will tell the tale.
You do not want a real fast timing curve. A smooth moderate curve, all in by 3000/3200 is better overall on the street, combined with the right amount of ported vacuum advance.
20deg vac advance may be too much on a non egr setup.
get an adjustable vac canister, 10 to 15 deg is usually better.

 

Forget the whole idea- 99 times out of 100 the limiting factor is NOT the slot! GM HEI distributors the limit is when the advance weight "tails" lock against the centerplate. The slot won't limit either the bottom or the top end of the advance- it's ALL the interplay of the weights and centerplate.

Sorry, another "old wive's tale" exposed. Wish it was as simple as this but it usually isn't. I've done millions of 'em, too.

An alternate method to get you where you want to be:

Advance initial timing 4* to get to total advance where you want it and then limit centrifugal advance by the same 4* to stay out of low RPM/part throttle detonation.

See the article on HEI performance in the tech section of this site for some more details on getting the "curve" dialed in how you want it.

 

Which springs do you suggest? I have a kit with 3 different ones, like most kits.

 

get an advance timing light. Try the two medium ones.

 

is it just me or has anyone else heard that you want all off the advance IN as soon as possible....if you can get it all in before 3000 then you are better off????

 

I got some timing tape yesterday so that should tell the tale. Now I have to head over to the pick-a-part and get a couple vaccuum canisters to wotk with. I'll probably get a couple 12 and 14 degree ones to replace my 20 degree one, and have some extras for the future.

I took a 50 min. round trip to the spped shop and it was barely pinging on the highway at tip in with the motor at about 210 degrees and 87 octane. The intial advance is set at 16 degrees and I am guessing the total centrifugal is 20 and then another 20 for the vaccuum canister so I'm at 16+20+20=56 degrees, I need 50-52 degrees I think for the best combination of performance and economy.

What do you guys think?

 

Think youshould put some better gas in it.
Just isn't worth a broken ring land to save a few pennies at the pump. 50 deg sounds good.

 

Today I went to Kragen and AutoZone to try and find a vacuum canister that would give me 14-16 degrees advance.

Apparently cars without emissions had less advance than EGR setups. I used a 76' camaro ( non CA) for the part#'s and here's what I got:

Kragen: Total aftermarket dist. = 15 deg. stamped on canister
Canister for non CA car= Non- Gm stamp ( Niehoff Ar-23) the slot looked considerable smaller than the canister for the EGR car
Canister for CA egr car= 18 degrees

AutoZone= all Wells part#'s

I ended up buying one that had AR-10 stamped on it because I remember the canister in my 91' RS having the same #. I also looked at a whole replacement and had a Gm reference # on it that said 10 degrees.

I figure I have no need for an adjustable unit. 10 degrees should be fine and would give me a total of 46-48 degrees.

 

Sounds good to me.