Pilot Dan

I currently have the distributor out of the 64 to inspect and address the centrifugal advance which was coming in way too early and have another question.

I've read everything I could find, but the end play measurement still puzzles me. Everything I read says .012-.017 is safe, Lars says .005-.007. Well If I am checking this correctly I get .050 and this is with approximately a .030 shim in place already. So for arguments sake, lets say I was looking for .010 (just as an example) would that mean I need to add .040 more shims thickness??

Now here is where I am really confused, I checked 3 other Chevy distributors I have (non Corvette) and they all had about the same spacing as this one pictured. I have also read others with this initial spacing who claimed it was correct for clearance.

Is the tighter clearance a Corvette tuning thing or was it made like that originally and this is just the result of wear??

I know there are some experienced guys on here who have written some great posts, please weigh in if you can to clarify this. Pilot Dan



Feeler gage spacing is .050 with a .030 spacer here.

Bluestripe67

I have mine set at .015. Is it right or wrong, I don't know, but it's been set like this for over 15 years and about 40k miles. Dennis

Powershift

I would shim it to around 0.010 to 0.015 inch, as Bluestripe recommends. Having said that, it will run okay as it is. You know that. But reducing the end play should/will reduce spark scatter and make for a better distributor.

Years ago, I shimmed my distributors as Lars suggests, and had no issues. However, a few "thousands" more will also be okay.

Not a Corvette thing..........Chevrolet and others provided plenty of gap/clearance from the factory. The racers liked to improve on what the factory provided and "make it better".

Larry

SupremeDeluxe

I always set them at 0.005-0.010. Easier to measure accurately with a dial indicator than feeler gages.

LI Corvette Supply used to sell a convenient kit with multiple shims of differing stock for this purpose. Not sure if it is still available.

DansYellow66

I would check free play installed in the motor with a gasket just in case it bottoms out on the oil pump drive when installed and tightened down. This is probably only an issue on motors that have had a lot of machine work done on them - but with 50 year old motors that could be most of them. At least make sure it has a slight amount of play and isn't binding. A few thousands clearance additional play isn't going to make any noticeable difference in engine performance.

Powershift

Supreme:

I KNOW that you do good work.................but you don't need a Starrett dial indicator to set the distributor end play.

A feeler gage is plenty accurate.

Larry

Pilot Dan

End play is the same installed as measured .

Pilot Dan

So a combination using multiple shims to take up the slack is the correct way to achieve that ?

Bluestripe67

Yes! I don't remember where I got my shims. Check on line or at a good engine shop. Dennis

Randy G.

Mine was .045. Why they are this much is beyond me. I dropped it to .015.

Powershift

LICS sells them. Part Number 48-26 A/B/C (depending on thickness). Years ago we just bought them over the counter at the Chevrolet Dealer. Try that now and see the parts guy's look when you ask for distributor shims..........

Larry

claysmoker

Summit and Jegs also sell the shims.

mhanley

Any local Speed shop should have the shims as well. I have mine set at .015.

Mike

redvetracr

Moroso shim kit #26140

VITIV Coupe

When I got my car last year, the distributor is the first thing I removed from the car to check. I had .045 end play, dropped it down to .010, and yes it should get rid of any spark scatter also.

Avispa

This is much more important than end play in the distributor shaft. There may be some spark scatter if the end play is too large, but it's negligible. The distributor shaft is pushed in one direction along its axis of rotation because of the tooth shape of the distributor gears, so the distributor shaft is not going to move up and down much when the engine is running. Bottoming the distributor shaft in the oil pump drive extension, on the other hand, is almost certainly going to result in something breaking along the oil pump drive extension or the oil pump drive gear. I had to put .130" worth of nylon washers under my distributor to keep it raised off the oil pump drive extension because of all the machine work on my block.

MikeM

Something I never see mentioned, that large end play in the specification could be to allow more oil to work it's way up into the shaft/bushing.

I think the Delco spec on the later aluminum distributors called for a range from about .030 to .080+ end play. Most of these had just one anti-rotation shim which took the end play to a nominal .060.

I'm of the same opinion as some others. Once the engine is fired, the drag of the oil pump will force the helical gear upwards and it will stay there as long as the engine is running.

If your timing happens to be more stable AFTER you shim it, it's because you just moved the shaft up higher on an unworn place and that effectively tightens things up. Short term improvement as that spot will wear quickly.

DansYellow66

Thank you - sometimes hard to cut through the everyone's tunnel vision.

Pilot Dan

I found some additional information which seems to confirm that the spacing I have is right in the middle of the GM manufacturing spec for a non fuel injected engine (.060). Now if you look at the 63 Corvette service manual (6Y-29), it states the end play spec as .002-.007 for distributor set up.

I don't think it has ever been explained with certainty why GM did not in production manufacture these distributors to the same specs that they state in the service guide.

Thanks to all who have replied.

MikeM

The cast iron (Corvette/pass car) used a different, much wider end play spec than the aluminum bodied distributor which wasn't used in C2 Corvettes.

There's other exceptions and confusion but I'm not going there today.