How to limit full advance on HEI distributor?

I heard about thst this can be achived by blocking, placing a pin? I need information on this..

Thanx in advance!

You can weld up one of the slots on the advance plate. You'll have to disassemble the distributor by driving the pin out of the gear on the end of the shaft. (Don't lose the shims.) There's an article with pictures in an old issue of Chevy High Performance magazine. It's in the "Agent 87" article-several years old. You can find it by using the search function on their website. Ultimately you'll still have to reassemble & check it with the engine running to see if you have the timing limited like you want. Or if you're lucky, you can find a shop with one of the Sun distributor machines that were around back in the 60's-70's. Good luck. Dave

I think that thid kit will help http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3085&prmenbr=361

Thanx!

There are other ways to do it also(including welding). The pin is already there and it basically rides in that slot that you would weld up(if you choose to weld it). Well, another way to do it is with a larger bushing. I didnt look at that kit in the link, but your typical advance curve kit does usually have a different bushing in it. The thicker bushing will effectively limit mechanical advance just like making the slot smaller(by welding) will do. There are a few good kits out there and Id get one cause they are cheap, and at the very least you will make use of the springs that come in the kit. And, try out the bushings first. IF they work, good, than you dont have to make any real mods. But if you dont quite get it right with the bushing(s) provided in the kit, than a little welding is in order. You can use JB weld.

Oh yeah, once you actually look underneath the advance weight mechanism it will be pretty self explanatory as to whats going on. So, you will find that it isnt that big of a deal to do either way once you look at it.

Try this out too.. Thanx!

The kit in that link is for MSD distributors only. Their distributors are set up differently than GM HEI's.

you can press a 3/16" spring pin in 1 of the holes in the advance plate to acheive what you want to do.

Awesome! Thanx.

Usually GM HEI's have just the opposite problem, not enough mech advance. Most have about 14 or 15 crankshaft degrees of mech advance from the factory. Keep in mind this was in the primitive smog emissions era. On the ones I've seen and set up, the pin and bushing never reach the end of the slot. The amount of mech advance is governed solely by the weights, weight cam, and springs. The aftermarket advance kits are only good for the springs and plastic weight bushings. The weights don't fit most GM HEI's. I suppose if you want even less mech advance than original you could weld the slot.

Nice info.

My HEI is Summit HEI distributor. I hope that this distributor have been refined and re-done to perform better that the stock "smog" time built ones. Like what it says that it has a 50,000v coil, blue printed, and a better module on it....

Update.

I have modified the distributor's mechanical advance. Limited the full advance, reading and adjusted and set the base at 16 deg and stop at 36 ~ 38 at full advance on wot. Performed excellent. My set up (2800 stall, TH350, 12.5:1 comp, prepped camel hump head, 286 .486 .486 106LSA Isky cams, & 2.73 open diff) achieved constant low 13s on G-Tech.

I will try better coils (currently stock due to burned 50,000 coil..) and module, better gears and a posi and see what happens.

The plate under the weights has a small hole on either side,I put a small zip tie through each hole to stop advance,had about 14* mechanical that way if I remember right.I use Mallory Unilites now though.

I used a tie wire. Sure worked.

Yep, the Unilite. I have that on the 68 383 camaro. Its a nice distributor combined with 6AL box.