So after Attempting to tune my car for a few years I decided to see if I could dial in my dizzy with a spring set.
The Thing has about 1/4 of shaft end-play. that actually explains some of the issues I've been dealing with.
(to much mechanical advance.. had to un hook the vacuum.. stil didn't run right............... on and on....with other attempts to dial it in including a carb change.... )

I have a New Pro Comp dist but after reading some horror stories I opted to just shelve it.

I planned on taking a run with the wife this weekend but I'd rather get this sorted out than cause damage or get stranded.

Should I try the Pro comp?
Is this much end-play able to be shimmed out?
Should I just say the heck with it and get another dist...
I really didn't plan on dumping cash into the thing but well ya' know how that is...

 

you have a new procomp, and you have one you cant get to work, why not put the procomp in and try it, most...but not all... horror stories are from folks who dont read the directions.
btw , read the directions

 

I've installed a few of the 40 dollar ebay cheapies for folks and have had no problems reported.
I wouldn't be shy.

 

HEIs are pretty simple,are you sure the reason the car is not running right is because of the distributor ?
Are you comfortable swapping a dist , some get them out and have trouble getting them back in and timed , read up first.

 

If you have a 1/4" of shaft end play on the HEI unit, there is something mechanically wrong with it. Until you figure out what that is and repair it, you should go with the ProComp unit. As mentioned, read the directions so that it will work properly with YOUR car.

 

I would take another look at your mechanical advance - tuning kits include a limit bushing if you're experiencing too much mechanical advance. End play wouldn't impact the advance curve, it just tends to show up in "jumpy" timing. Unhooking your vacuum advance is definitely a Bad Idea; an adjustable vacuum advance is also available, and also has a limit mechanism (that's kind of a pain to use) if needed.

It's not all that unusual to have a fair bit of end play in a stock HEI distributor. 1/4" is definitely more than average if it's really that big of a gap...a shim kit is not going to take out that much play. If it's less on another look, shim kits are cheap and shimming the shaft is simple - just drive out the drive pin, slide on the required shims and drive the pin back in.

I bought one of the Skip White distributors off eBay based on feedback from another site and it was a ProComp. I drove out the pin just to get a look inside and wasn't impressed. The external body machining looked good, but inside the bronze bushings were driven in cockeyed and there was a TON of machining debris inside the body. I expect it would work OK...but I would probably pass based on the bushing as I don't expect great longevity. The MSD StreetFire is a great investment - but otherwise any brand-name HEI is fine.

 

Here is another little bit of information that I found out that hard way about the ProComp distributor.
The pick up coil in the Procomp distributor has a smaller hole in it than the oem part.
If you ever have to replace the pick up coil with a parts store replacement hei part, it will fit sloppy loose in the Procomp housing.
As soon as I discovered that, my Procomp HEI became a spare part only to be used in case of emergencies.

 

I Bought a MSD Street fire and have a question.
If I set my base at around 10-11 and the centrifigal bring me to 31 (the msd doc states that the mechanical advance has 22 degrees) I'm already at 33... then If I use the limit plate on the vacuum advance that brings me to 38 degrees total.
Isn't that way to high?
So are these things sold with to much advance out of the box???/
What the hay..

 

I had the same end-play problem, but I didn't know it until I had my car on a dyno. With my dizzy, the end play was caused by a vertical shim problem. I bought a shim kit (Moroso, I think) and ended up putting almost all of the shims in. That fixed the problem.

 

The timing sticky is a good read, as is Lars' paper.

http://forums.corvetteforum.com/c3-t...long-post.html

The quick answer is no, that's not too much advance. As a general rule of thumb, you're looking for around 34-36 total advance in before 3,000 RPM. This is set with vacuum advance disconnected.

Vacuum advance is adjusted after inital + mechanical is done; vacuum will bring total advance to 50+ degrees during part-throttle operation. Sounds nuts, but there it is.

 

At WOT, engine vacuum is very low, so not vacuum advance is added to ignition timing. As rpm increases, vacuum also increases and timing advance increases. But, at higher rpms, that increased advance can be tolerated.

Just 'Google' "distributor timing advance" and read up on it.

 

I've read many things in the last week this summary above helps a ton..it explains the vacuum thing well.

 

If you e-mail me a request for my timing papers, I'll send you current versions that explain it all. The papers posted on this Forum are obsolete and outdated.

Lars
V8FastCars@msn.com

 

Email sent. Thanks Lars!

 

Lars, do you have a paypal to send you a beer?


I've dialed out any hesitation from my carb /Dist... (demon 750 vac secondary) and have my timing almost perfect. Again, no hesitation awesome startup and NO HESITATION.. but I need to get the timing in earlier with the spring kit to get abit more crist response (I bough it but have not had the chance to install it).


It's close and 100% better than EVER BEFORE.. .
I have a fairly decent understanding about setting timing for performance thanks to you guys!!!
By the way, I did limit the vacuum advance with the plate to 10*

***For the record and others..***

This is a 383, 010 block, scat forged crank & rods / stock vortec heads / L79 grind cam (old school wolverine 327/350hp) msd streetfire dizzy / BG speed demon 750 vs carb. Th350 tranny 2200 converter.

Initial ended at 10*, 22* for the mechanical and 10 for the vacuum advance.
brings me to 32* total no detonation. ( I did not try 34* total yet but could)

Again,

Thanks a ton guys!.