73 L82 camshaft gear nylon?

[Russ S.]

Gentlemen, My 73 has 70000 miles on the clock and the engine has never been opened up. I am thinking that it came from the General with the nylon camshaft gear and am getting to the point that I don't dare drive it due to that gears chance of failing. Can you gents tell me if it does in fact have the nylon gear?

[Joe L.]

Re: 73 L82 camshaft gear nylon?

Gentlemen, My 73 has 70000 miles on the clock and the engine has never been opened up. I am thinking that it came from the General with the nylon camshaft gear and am getting to the point that I don't dare drive it due to that gears chance of failing. Can you gents tell me if it does in fact have the nylon gear?

Russ------


I can virtually guarantee you that it was originally built with a nylon-toothed camshaft sprocket.

GM used nylon-toothed camshaft sprockets in PRODUCTION on all 1966 and later small blocks as well as all 1965-74 big blocks. The entire camshaft drive system was designed to minimize noise as much as possible, including an early link/Morse type chain and a powder metal crankshaft sprocket. Personally, I don't recommend using any of these components when rebuilding an engine. I use ONLY Cloyes True Roller timing sets. Period.

[Russ S.]

Re: 73 L82 camshaft gear nylon?

Thanks Joe, That is what I was thinking. Just didn't realize GM used them way back to 66. Thanks

[Ray G.]

Re: 73 L82 camshaft gear nylon?

Russ
We replaced many of those nylon gears at the time, usually when the rounded camshafts lobes where discovered. At the time we noticed the engine sometimes ran quite a few miles, as long as the RPMs were low, with the nylon outer edge falling off in pieces. Sometimes the pieces would restrict the oil flow return coming down from the lifter gallery. The crankshaft seal would then leak more causing the owner to bring the car in for excessive oil leak and consumption.

[Gene M.]

Re: 73 L82 camshaft gear nylon?

I think they were all nylon coated teeth except pick up trucks.

[Peter G.]

Re: 73 L82 camshaft gear nylon?

Russ are you talking about the timing gear in the cover on the cam shaft...if so I replaced my gear in my 1972 Impala Caprice with a small block 400. The gears were all nylon coated teeth and I replaced with the all steel gears. Of course the nylon was laying in the bottom of the cover with very little left on the gear.

[Ray G.]

Re: 73 L82 camshaft gear nylon?

You are correct Gene. I should have written "nylon coated teeth on the gear".

[Joe L.]

Re: 73 L82 camshaft gear nylon?

You are correct Gene. I should have written "nylon coated teeth on the gear".

Ray-----


Well, actually somewhere between nylon teeth and nylon coated teeth. The teeth were mostly nylon. The aluminum hub had only small "spurs" at the position of each tooth.

[Russ S.]

Re: 73 L82 camshaft gear nylon?

Yes Peter. I had hoped the old General would have put decent parts in their optional engines as they did in truck engines. Guess I will need to tear it apart.

Russ are you talking about the timing gear in the cover on the cam shaft...if so I replaced my gear in my 1972 Impala Caprice with a small block 400. The gears were all nylon coated teeth and I replaced with the all steel gears. Of course the nylon was laying in the bottom of the cover with very little left on the gear.

[Joe L.]

Re: 73 L82 camshaft gear nylon?

Thanks Joe, That is what I was thinking. Just didn't realize GM used them way back to 66. Thanks

Russ-----


Yes, 1955-65 small blocks used a cast iron cam sprocket. Beginning in 1966, this changed to an aluminum cam sprocket with nylon teeth. 1966 was actually unique because not only was it the first year for use of the nylon-toothed cam sprocket, it was the last year for the "wide" sprocket timing set for small blocks. "Wide" sprocket, early link timing sets were never again used on small blocks after 1966. For 1967 and later, the "narrow" sprocket timing set came into use for all small blocks (except truck applications using a "roller" timing set).

For big blocks, it was a little different. All 1965-66 big blocks used a nylon-toothed cam sprocket with a "wide" timing set. For 1967-74, things changed. All L-36, L-68, LS-5 and LS-4 used nylon toothed cam sprocket with a "narrow" timing set. L-71, L-89, L-88, ZL-1, and LS-6 used a nylon toothed sprocket with a "wide" timing set. Yes, that's right----L-88 and ZL-1 used a nylon-toothed, aluminum hub cam sprocket!

Below see examples of the 1966-only "wide" and 1967+ "narrow" small block cam sprockets.

[Russ S.]

Re: 73 L82 camshaft gear nylon?

L88s and ZL1??? Crazy! Thanks, Joe. Don't know where you get all that great info!

[Joe L.]

Re: 73 L82 camshaft gear nylon?

Yes Peter. I had hoped the old General would have put decent parts in their optional engines as they did in truck engines. Guess I will need to tear it apart.

Russ------

As I mentioned, I believe the use of the nylon-toothed cam sprockets was instigated by a desire to achieve as quiet of engine operation as possible. This is very important for passenger cars, including Corvettes. Many PURCHASE DECISIONS might be influenced by quiet engine operation. Even the minute amount of extra "quietness" provided by the nylon-toothed cam sprocket and Morse type timing set was probably seen as being very important in a competitive environment. For trucks in the "old days", quietness was probably of lesser import and durability of greater import. However, not all trucks got the roller chain; many after 1965 got the same timing set as passenger cars.

These days, if one wanted to rebuild their small block engine with a nylon-toothed cam sprocket, they'd have a tough time. The nylon-toothed sprockets are very difficult to obtain. GM discontinued the small block nylon toothed cam sprockets for SERVICE in the early 70's and replaced them with the cast iron type. They continued to use the nylon-toothed sprockets for PRODUCTION but, for SERVICE, you got a cast iron sprocket. You see, for SERVICE, quietness is not so important. By the time someone needs a camshaft sprocket for SERVICE, they already own the vehicle. Most, if not all, aftermarket sources have now discontinued the nylon-toothed cam sprockets.

[Joe L.]

Re: 73 L82 camshaft gear nylon?

L88s and ZL1??? Crazy! Thanks, Joe. Don't know where you get all that great info!

Russ-----


The part number was GM #3856356 and it was the same sprocket used for all 1965-66 big blocks. Later, the part was superceded by GM #330815 which was discontinued without supercession about 20 years ago.

[Russ S.]

Re: 73 L82 camshaft gear nylon?

Joe, I see in past posts you recommend the 9-3100. What is the difference between the 9-3100 and the 9-1100? Thanks.

[Joe L.]

Re: 73 L82 camshaft gear nylon?

Joe, I see in past posts you recommend the 9-3100. What is the difference between the 9-3100 and the 9-1100? Thanks.

Russ-----

The 9-3100 has higher quality components. In particular, the chain is a much higher quality piece. It used to be manufactured by Renold but now they have switched to another high quality chain manufacturer.

However, the 9-1100 is a completely adequate set and will likely have a life much longer than any of us are going to need it and will perform perfectly. Nevertheless, for me, I use the 9-3100 exclusively for small blocks. Yes, it costs about 60 bucks more than the 9-1100 but, to me, it's worth it. But, about certain things, I'm an "overkill" kind of guy.