Anyone Used a Nylon Cam Button?

[ChevroletR]

I'm doing a COMP Cams retrofit roller swap and I'm running the Edelbrock two-piece aluminum timing chain cover: http://store.summitracing.com/partdetail.asp?part=EDL%2D4242&autoview=sku

 

Edelbrock tells me to use a nylon cam buttom, which COMP happens to make:http://store.summitracing.com/partdetail.asp?part=CCA%2D202&autoview=sku

 

With my timing chain set, I had to grind down a good bit of this cam button to get it to fit under the cover. I was wondering how much clearance or endplay of the camshaft/cam button should I have? Thanks

[wallaby]

The Comp catalog says different buttons are available for different types of timing cover designs. (maybe why you had to shorten yours)...anyway I don't see that it would matter.

 

The Comp catalog says its roler cams should be set up with an endplay of .004 to .010

 

They also go into the fact that checking Chevrolet endplay is a pain because it needs to be done with the timing cover installed. Maybe the inside surface of your cover is flat and you can just use a straight-edge and feeler gauges? Comp wants you to use a dial indicator and put it through a hole in your cover to measure the endplay as you lever the cam back & forth from the lifter galley with a screwdriver. They suggest a pipe plug to fill the hole afer you're done.

The one thing they forgot to mention is that you wouldn't want to make the hole in your cover in the center! You wouldn't want your thrust button riding on the backside of the pipe plug.

 

I found this at the Comp Cams site under the heading of "Instalation instructions":

Checking Camshaft Endplay

Camshaft endplay refers to how much a roller cam is allowed to move back and forth in the engine.

.005” to .010” endplay is required to eliminate the possibility of wear occurring as a result of

interference between the cam and other engine components. Excessive endplay is detrimental as the

cam will be misaligned to the lifter bores, causing the roller wheels on the lifters to run off the edge of

the lobes instead of on the center. Another important effect of camshaft endplay is that as the cam

moves back and forth, it advances and retards the ignition timing at the distributor gear.

The proper amount of endplay is between .005” and .010.” This can be checked using a dial indicator

and magnetic base on the front of the engine. To do this, push the cam as far back in the engine as

possible, zero the indicator on the upper timing gear, and then pull the cam as far forward as it will go.

The indicator reading is the amount of endplay in the camshaft.

In Chevrolet engines, the front cover must be in place to check endplay because it is the front stop for a

roller cam. A cam button is used to take up the additional space between the timing gear and the front

cover. These are typically made of Teflon™/fiber or steel. The steel buttons have a miniature roller

bearing built in. All types are available from COMP Cams® in various lengths, depending on what

front cover you are using.

The Chevrolet front cover design makes using the dial indicator technique of determining endplay

difficult. Some of the front covers have an access hole with a pipe plug in it to allow a dial indicator

extension to go through the hole and contact the upper timing gear. The stamped covers have no such

provision. An alternate technique that can be used is to gently insert a long screwdriver in one of the

lifter bores and carefully pry the cam back and forth using the sides of the lobe in the bore. Do not use

excessive force to try and move the cam. Estimate how much endplay exists from the movement of

the lobe, and adjust accordingly. If the endplay is too much, install some suitable shim material behind

the cam button and recheck. If it is too small, carefully remove some material from the back of the

cam button, reinstall it in the timing gear, and recheck.

One final note of warning, stamped steel Chevrolet front covers are typically very flexible where the

cam button contacts them. This is detrimental to maintaining a consistent amount of endplay.

Washers are available to weld inside the cover to stiffen it. Also, the water pump fits tightly to some

front covers and can act as a support. For most race type roller cam applications the use of a cast or

billet aluminum front cover is strongly suggested to eliminate any front cover flex-induced change in

endplay. COMP Cams® offers two and three piece billet aluminum timing covers for big and small

block Chevrolet engines.

[ChevroletR]

Wow, thank you Wallaby...that's an interesting find. The only think I checked was by using Play-Doh and pushed my timing cover on until I knew I had ground my cam button down far enough where it wouldn't push the cam button out. I didn't check endplay or how far the cam would move though...

 

Also interesting about the cast or billet aluminum timing cover and the flex that a stamped cover can have. I for one am using that STAMPED aluminum Edelbrock cover and am wondering before I install this cam again, should I look into a beefier cover? I'm thinking so...

 

Thanks again!!

[ChevroletR]

When do I know if I need a steel roller, aluminum, or nylon cam button? My Edelbrock stamped steel timing cover calls for strictly ONLY a nylon cam button, but I was looking at cast aluminum covers and they don't specify. Wouldn't the nylon or aluminum cam button be best for an aluminum timing cover?

[wallaby]

You don't want to run aluminum against aluminum! That combination is probably the worst I can think of. When aluminum rubs against aluminum it just tears itself up. It galls and gouges and scores and rolls into little balls....(like the inside of a Vega engine. LOL)

 

As a general rule, you don't want to have similar materials rubbing together...ever.

 

I think I'd use the nylon button. It's a safe choice for whatever cover you decide to use, and it has no moving parts.

[ChevroletR]

Awesome, that's the reassurance I need to hear! lol thanks