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Discussion Starter #1
How important is the end play on the HEI? I'm running an original dist with plenty of space between the driven gear and the thrust washer. Does this make any difference once the gear is turning? I imagine it holds the shaft in one position as long as it's spinning.

Thanks,
-Michael
 

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mhamilton said:
How important is the end play on the HEI? I'm running an original dist with plenty of space between the driven gear and the thrust washer. Does this make any difference once the gear is turning? I imagine it holds the shaft in one position as long as it's spinning.

Thanks,
-Michael
The gears will tend to climb up the teeth and that will alter the timing. I try to shim to about .030 ? (I think) vertical slop in the shaft, to give the aluminum housing room to grow when it gets hot.

Anybody else got a spec for this? I haven't done one in a long time. TOM?????
 

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mhamilton said:
Thanks for the quick reply--

I can't belive this... since I posted, the forum finds the info I'm looking for (down below) http://www.hotrodders.com/forum/hei-shaft-play-36106.html I had searched before posting, found nothing.

Are the mail order catalogs the only place to get the shims?

GSXMAN said .012-.020. !!!!!! Thanks for the refresher. :thumbup:

Maybe O'Reilly's or Auto Zone in their performance section. Call around local.
 

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Discussion Starter #6
Mr Gasket # 2820 is a dist gear shim set we stock/use
Sorry I missed your post... just an hour ago I put an order in to Jegs for the shims. Of course they took me to the cleaners on shipping for a $5 part.

Well, I have other cars that I need to check the HEI on, I'll pm you.
 

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I followed the advice of my buddy Steve and keep the endplay on my distributors to between .004-.008,and I too have used washers but could never find any the right size and had to drill/grind for a good fit.Last time I got a Moroso kit with different size shims.
 

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Discussion Starter #10
What causes all the slop in these distributors? Is it wear of the gear, or is there a bearing surface under the timer core?
 

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Alloy dissys wear faster than iron ones. I keep endfloat down to .012 inch, any less and they can bind when hot - over 120f ambient. Too much endfloat will create top end retard as the drive gear is repelled off the cam in an anticlockwise direction.
BTW, Pontiacs with an anticlockwise dist rotation (wrong side of the cam) get top end advance with too much endfloat.
 

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IanRiordan said:
Alloy dissys wear faster than iron ones. I keep endfloat down to .012 inch, any less and they can bind when hot - over 120f ambient. Too much endfloat will create top end retard as the drive gear is repelled off the cam in an anticlockwise direction.
BTW, Pontiacs with an anticlockwise dist rotation (wrong side of the cam) get top end advance with too much endfloat.
There's a good piece of information. Thanks..

I guess .020 is the consensus, right?
 

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Discussion Starter #15
Got my shims all installed this afternoon. My end play was enormous--something like +0.070 in. I used the 0.05" and the 0.020" shim to bring it to a clearance of ~0.018". Definitely accelerates smoother, and seems to be a bit smoother cruising at highway speeds.

Also re-cleaned the mechanical advance, that was getting a bit sticky again. I think it's time to give up this Chevy HEI and get a nice Eldorado with Electronic Spark Selection :D
 

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I'm glad I ran across this older thread. I recently replaced my factory (crate assembly) Chevy ZZ4's HEI distributor with an MSD unit. It took less than a thousand miles for me to notice a little tach bounce. The engine's been running great. Out of curiosity, I removed the cap and rotor and discovered the same vertical end play as the old distributor that had given me nothing but grief. At the time of the replacement, I had not heard of shims. Now, I can rescue this distributor before it's too late.
 

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The first thing I checked on my PerTronix Stock Look distributor was the thrust clearance (end play). The thrust clearance was .020” out of the box, so I did not have to shim the gear.

A new GM point type distributor cam be as much as .025” - .030” thrust clearance. That is due to the GM sloppy assembly line production standards.
 
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