camshaft gear 73 L-82 Plastic?

[Russ S.]

Gentlemen, Was the camshaft gear on 1973 L-82 of the plastic variety? My L-82 hasn't been opened up at all and it was suggested to me that I need to replace the "plastic" cam gear. After all these years that seems like a very good suggestion as I know they come apart. Thanks

[Joe L.]

Re: camshaft gear 73 L-82 Plastic?

Gentlemen, Was the camshaft gear on 1973 L-82 of the plastic variety? My L-82 hasn't been opened up at all and it was suggested to me that I need to replace the "plastic" cam gear. After all these years that seems like a very good suggestion as I know they come apart. Thanks

Russ------


The original camshaft sprocket for your L-82 application was an aluminum core with nylon (plastic) teeth. You can no longer obtain this type sprocket from GM and you will even have difficulty finding one in the aftermarket these days. I don't recommend them, anyway.

My preference is a Cloyes True Roller timing set.

[Dan D.]

Re: camshaft gear 73 L-82 Plastic?

We used one of those aluminum/plastic sprockets briefly in our stock car back in the days (late 60s). Didn't last long. Broke all to hell in no time flat. Don't use it. -Dan-

[Russ S.]

Re: camshaft gear 73 L-82 Plastic?

We used one of those aluminum/plastic sprockets briefly in our stock car back in the days (late 60s). Didn't last long. Broke all to hell in no time flat. Don't use it. -Dan-

I agree Dan. I never had any intention of replacing it with another plastic one. My question was does it have one? If it does then I do need to replace it with a better one.

[Joe L.]

Re: camshaft gear 73 L-82 Plastic?

I agree Dan. I never had any intention of replacing it with another plastic one. My question was does it have one? If it does then I do need to replace it with a better one.

Russ------


Your application was definitely originally equipped with the nylon-toothed sprocket. However, if you find anything else in there, it means that someone was in there before you and replaced it. The gear available from GM for many years has been cast iron and the one commonly available in the aftermarket is cast iron. The cast iron sprockets are a direct replacement for the aluminum/nylon and can be used with the same chain. Whenever any of the three components of the cam drive needs to be replaced, though, it's foolish not to replace the complete set.

The main purpose for the early link, otherwise known as a Morse, type chain and sprockets is QUIET OPERATION. To help achieve this, the camshaft sprocket is nylon toothed and the crankshaft sprocket is powder metal. In addition to the well-known problems associated with the nylon-toothed cam sprocket, tooth loss is also a problem for the crank sprocket (see attached photo of an original GM sprocket removed from an engine). The early link type chain is also highly susceptible to "stretch". Ever notice a timing mark "jumping around", even slightly, when you have a timing light on an engine? Chain "stretch" is usually the cause.

A Cloyes True Roller timing set 9-3100 solves all of the above and there is absolutely no discernable difference in the noise level over the stock-type chain. This set uses a case hardened nodular iron camshaft sprocket balanced to 10,000 RPM, a steel crankhaft sprocket, and a VERY HIGH QUALITY Renolds true roller chain.

Also attached is a photo of a new aluminum/nylon camshaft sprocket. Pay no attention to the 340235 part number seen on this sprocket. That's actually the GM part number for the CAST IRON sprocket. How it ended up on this sprocket I have no idea. The original GM nylon sprocket used for 1967-82 small blocks was GM #3896960. It was discontinued from SERVICE in February, 1975 and replaced by the cast iron 340235. However, the 3896960 continued to be used in PRODUCTION for a LONG TIME after it was replaced for SERVICE. You see, the cast iron camshaft sprocket with an early link-type system is a little noisier than the aluminum/nylon and GM wanted PRODUCTION engines to be as quiet as possible. For SERVICE, quiet operation is not so important (after all, they've already sold the car by that time) and nobody really wanted a nylon toothed sprocket, anyway (after they saw the one they removed from their engine).

[Russ S.]

Re: camshaft gear 73 L-82 Plastic?

Thank you Joe for all the great info. I know it hasn't been changed and the car has 70,000 miles and 38 years on it so I am surprised that it hasn't gone south on me long ago. Thanks.