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Discussion Starter · #1 ·
I finally got my new motor in my S10 but noticed the timing was jumping around @ 3000 rpm and above. I considered two possible reasons for this happening.
1. Cam walk
2. Distributor gear end play.

So I pulled the distributor out at about 300 miles and noticed a lot of wear. :nono:



It had a good amount of end play on the gear shaft so I locked out the distributor (MSD 85551) and shimmed the gear. Slapped her back in and was happy to see rock solid timing and the motor just ran better.

I am hoping this solves the problem if not what are some other things to consider if the gear keeps wearing down fast?

I almost want to get a belt drive for my timing to ensure my cam is not walking If the problem keeps happening.
 

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Install a Comp Cams Ultra Poly composite gear for extended distributor driven gear life. Use CC-12140 for a .500" shaft or a CC-12200 for a .491" shaft.

Bronze driven gears like you have are sacrificial and are designed to wear rather that wearing out the non-hardened steel billet camshaft drive gear. Since steel billet camshafts are designed for drag race only, the bronze distributor gears often used with those camshafts are routinely inspected and replaced.
 

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I see that distributer has an o ring on it. I cut a very small groove in that bottom cast part to add some oiling on that gear. Maybe remove that o ring and add a groove (on the camshaft side of the distributer)

Maybe just me, but I don't think I ever saw a Chevrolet distributer with an o ring there.
 

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Discussion Starter · #6 ·
Thanks for the replies everyone, I ordered another bronze gear before I was introduced to composits. But if its still a problem I will try the composite gear next.

What about a belt drive to cut down on cam endplay? And how safe is that for street use?
 

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What about a belt drive to cut down on cam endplay? And how safe is that for street use?
You should have between .001 - .005" end play with a roller cam, you don't say what you cam or how much end play you have. Any more than that you need the correct thrust button to control end play, either a roller with shims you can remove or different size teflon buttons.
 

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Discussion Starter · #8 ·
I have no idea what the cam end play is. The motor was built by a highly respected engine builder in our area. He assured me the end play was correct. The only end play I could measure without pulling a lot off was the distributor and it was .067
 

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I would get rid of that O-ring as well. The o-rings are only supposedd to be used in SBC's if the oiling has been modified, no mods, no O-rings.

If O-rings are usd on the distributer, you MUST chamfer the top of the distributer hole, as well as the top and bottom edges of the oil gallery down inside the oil. So 3 chamfers total are needed to run o-ringed distributers.
Using o-rings improves oil control through the engine, not using O-rings gives you normal oil pressure
There is a 0.030" hole at the bottom of the distributer that sprays oil onto the distribter and cam gear assembly.

I just read this info in GM's "Chevrolet Power" book p/n 24502488 on page 90.

On the 86+ roller cammed engines, used roller camshafts used high carbon steel instead of cast iron, in order to stand up to the smaller contact area of teh roller lifters. This high carbon steeel bar stock was induction hardened to Rockwell C-60 hardness. There for a softer ditributer gear MUST be used. GM used a melonized distributer gear on production roller cammed engines, bronze will work, but will limit durability.
There is a 0.500" 0.491" and the weirdo 0.427" Vortec(flat cap crab cap 96-2002 305/350 Vortec) distributer shaft sizes.
The composite gears work also,but are expensive.

peace
Hog
 

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Discussion Starter · #10 ·
Yep the o rings need to go like suggested. Plus Comp Cams highly recommended that I go to a composite gear like MouseFink pointed out for street use.



She is getting there but man still a lot to sort out. 2nd fuel cell/ pump for N20 rerun the fuel lines and so on.

Thanks for the help I will update everyone with the progress :D
 
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