[jonmachota78]

http://forums.maxperformanceinc.com/...ng+plate+screw

See attached thread ^^^^^^ has anyone done this with an HEI?
Im going to give it a shot. I'd like to hear of some accounts/successes/failures/issues/tips etc if there are any that may save time in my efforts. Ill post pics of my mess afterwards.

[Formulajones]

There is a much much easier way.

Tap an existing hole in the HEI cam plate that isn't used. It's already perfectly sized for a 10-32 tap. Just tap it and install a screw. This limits total advance to 18 degrees. Works slick and takes 3 minutes. Here's an old pic, I've been doing HEI's this way for years.

[jonmachota78]

That looks like an excellent idea, formulajones. Thanks for sharing, I'll consider the option

[frankyboy455]

do you mean 18 degrees of "travel" ?

[Sun Tuned]

Now do it with the head of a fillister head screw with the head of the screw on the topside....

File a flat on one side that touches the plate when it rotates over and contacts the screwhead. File to fit.

Haven't figured out why no one thought of this any sooner.

Take it one step further and cut different sizes (diameters) of the heads on a lathe and have different degree screws....

This is too easy.

[Sun Tuned]

Been doing this since 1977 on circletrack cars.

[Sun Tuned]

And before anyone asks yes each center cam results in different numbers with each lathe it screw.

And yes, I made a chart as such many years ago with 63 center cam numbers and the corresponding screw head diameters used to give "X" degrees.

[Formulajones]

Frank, by 18 degrees I was referring to centrifical advance. Using the 10-32 screw upside down like this has always yielded me ~18 degrees. Which happens to be right where I like to start when tuning a car. I dial in 14 degrees of initial and have 32 total to start Work my way up.

If I want more centrifical with less initial, I'll simply file that screw, as you can see in the pic I've done this already on this example. Doesn't take much.

Very simple mod. Every car with HEI I've tuned has over advance issues and pinging (cheap plastic limiter bushing always falls out) I'd have this trick done in a few minutes, and once finished you don't have to fool with it anymore. Apparently Sun Tuned has been aware of this as well

[zeebo]

Originally Posted by Sun Tuned

Now do it with the head of a fillister head screw with the head of the screw on the topside....

File a flat on one side that touches the plate when it rotates over and contacts the screwhead. File to fit.

Haven't figured out why no one thought of this any sooner.

Take it one step further and cut different sizes (diameters) of the heads on a lathe and have different degree screws....

This is too easy.

fillister screw?

[grandville455]

Here ya go

[jonmachota78]

Wow im sure glad I axt! Thanks guys, it looks like I'll be taking that route instead, it looks like way to go. Jon

[Sun Tuned]

Well as fjones said it's fairly easy. Quick, and no power tools. Easily reversible.

Closer to the 18 degree mark it does work better like he has it as you'll likely remove most of the head the other way any way.

Lil blue loctite for the nervous ones of the bunch, and a few extra for the cut to the chase ideas and your good to go.

[Cliff R]

Certainly LOTS of ways to skin this cat.

Here is what I do with them here, takes seconds if have a good MIG welder and round file.

We don't consider a "positive stop" optional on the HEI's, especially if you are going to lighten things up and use aftermarket springs on it. They can, and will allow the weights to "roll out" on the tips where they contact the center cam, and add a LOT of timing at really high rpm's.

I've observed this on the dyno, and why we provide the "positive stop" for them with zero exceptions.......Cliff

[Sun Tuned]

There are at least 5 other ways that haven't been mentioned....

We probably will need another cat to proceed with those methods though, we don't have enough skin left on the one we workin on.

Anyway you guys look like you're headed in the right direction... Carry on.

[john65ss]

I've seen other self-0proclaimed ignition experts say that a positive stop is all wrong for HEI, and that you MUST limit advance by selecting the proper centerplate and weights. Never made much sense to me. What do you guys think?

[Sun Tuned]

I prefer to use a specially designed plate we have made here and then have heat treated.

No worries here with that deal at least till 9-10,000 rpm.

As cliff will agree , almost any center cam that is used with a super light set of springs will allow extra advance, even mine, but I don't like light springs anyway.
They're not needed if you got the right parts to begin with.

If you want 100% dependability that you can stake your life on, then a mechanical stop should be in your future, whether you weld it, epoxy it, screw it, or whatever.
There is cut and try with all of it, you just have to deal with it as such. I dislike the mechanical means on a circletrack car for a couple of various reasons but there are ways around that deal although nothing too cumbersome if implemented.

Still for what I do here the properly shaped/engineered center cam is the way we do it here, the folks over at Performance Distributors are in complete agreement on this also.

I never proclaimed anything.

[Cliff R]

Correct, light springs can and will allow the weights to "roll out" on their tips past the "flats" on the center cam. The cam and weights used play a role here, but it NEVER hurts to add a positive stop at the exact location to make sure this NEVER happens.

It has no negative effects anywhere else as it only makes sure the pin in the advance slot hits the stop at the same moment that the weights reach their correct position on the center cam being used.

I've done enough distributors in the last three decades to fill up the bed of a full size pick-up truck, and never once has adding a positive stop caused any issues with the advance curve or correct distributor function.

I have seen all other sorts of lesser methods used, and I'm really not very fond of any of them.

Not fond of really light springs on HEI's either, and ALL of the generic aftermarket weight/spring kits are complete JUNK from what I've seen here.

The factory used really nice and correct hardened internal components in the HEI's. The down side is that the weights will often eat up the softer pins in long term use. The pin holes get "egged" out some as well. Neither of these deals is a showstopper, as we can replace the pins and braze up the weight holes and re-drill them (now they have a nice brass bearing surface).

I also see a LOT of damaged shafts and worn lower bushings. In most cases we can install a new bushing and clean up the shaft to get the side play reduced, but in many cases the shaft is worn undersized and damaged bad enough it needs replaced.

I'm currently very low on used cores to steal shafts from, and completely out of lower bushings, and really not doing too many HEI's these days anyhow. I have too much work in other areas, and I'd rather folks sent them to Sun Tuned instead......Cliff

[Sun Tuned]

Thanks Cliff! That previous post wasn't a poke at you or anyone ,just in a hurry and on my phone when I sent it.

I'm getting pretty behind on just those myself... Middle of racing season ya know.

Not much money in repairing shafts and pins, least not "as much as carbs anyways" ��

Seriously you gotta work really hard on those little areas and there is very small gain but then such is life. However worn shafts and pins can cause serious tuning problems if left unattended. The pin deal I got covered, and recently just been playing with the worn shaft deal over the winter. Pretty sure I got that one solved too.

At least sure enough I think I'll start offering a small bounty on original GM shafts. Not as high tech as the bearing deal you guys did but oem spec at least and way better than worn out.

Anybody got an abundance of them lemme know I could use a bunch of Pontiac shafts....

It's all good people, no worries.

[455Darren]

Thanks for this post! Was checking timing on my car and noticed a big increase in timing after 2800 RPM. Looks like I have some work to do on 3 distributors now......

[GOLDOHC]

Years ago I worked at a GM dealership, we installed distributors kits. The kit had plastic bushings that slid over the worn pins, then we drilled out the weights to fit over the bushings. I think the kit came with new springs. I don't know how long that fix worked or if that kit is still available.