Timing chain and gear for 1970 LT1

[Kenneth H.]

So I searched the forum and didn't find anything specifically addressing the timing chain and gear for my '70 LT1. I'm trying to find the part numbers and a source for these parts. I did see Joe Lucia's posts identifying the Cloyes 9-3100 timing set for the 350 HP engine but I wasn't sure if it was also good for the LT1 engine. Also, when I did an internet search for the item I saw that the 9-3100 was listed as is (9-3100) but also with a -5, -10 and -15 sub part number (9-3100-5, 9-3100-10, etc.) and I wasn't sure of the difference.

Can anyone help me with this?

Thanks

[Kenneth H.]

Re: Timing chain and gear for 1970 LT1

So I figured out what the -5, -10 and -15 represent. These part numbers identify 9-3100 timing sets with reduced center distance, for example the -5 is .005 reduced, the -10 is .010 reduced, etc.

[Duke W.]

Re: Timing chain and gear for 1970 LT1

NAPA currently offers the second design OE silent chain with a steel crank sprocket and cast iron camshaft sprocket. The chain is slightly narrower than the first design that was used through about '64. In the '65 time frame the second design silent chain was released with that horrible nylon tooth cam sprocket, but those are long gone, other than the few that are still in engines and waiting to fail. The current replacement second design chain has a cast iron cam sprocket.

Another option is the traditional truck roller chain. Silent chains were used on passenger cars since they are quieter, but on a mechanical lifter Corvette with loose fit forged pistons, you won't know the difference. In fact I doubt if there is a detectable difference in noise on a mild base engine.

Either set can be purchased for at little as about $15, and there are also sets that have multiple cam sprocket holes to advance or retard the cam four degrees.

I don't understand the obsession with Cloyes aftermarket chains. Though they have larger rollers (.250") than OE truck chain (.200"), is it really "better" at four to five times the price, and there are reports that the Cloyes 9-3100 can interfere with the timing cover because of it's larger OD. Either of the above OE replacement chains will outlive most of us in typical vintage Corvette service.

Cloyes also makes reasonably priced OE replacement chains - both the silent and roller type - and, in fact, I suspect the NAPA sets are just a reboxed Cloyes OE replacement sets sold under the NAPA brand.

The Chevrolet Power Manuals from the seventies, when production engines were fitted with the junk nylon sprocket, recommended using the early wide silent chain, which was still available through service parts at that time, or the truck roller chain for high performance and racing engines.

You can check offerings at www.napaonline.com and other retailers online catalogs.

For your application I recommend the NAPA NTP 9163, or Cloyes C3023K. I believe these are all the same parts manufactured by Cloyes and are typically less than $20 for the complete set.

Of note: The last time I looked into timing sets, NAPA offered OE replacement sets under the Sealed Power (Federal Mogul) brand, but I had a hunch they were reboxed Cloyes OE replacement sets. The Sealed Power catalog no longer lists timing chains for small blocks.

Reduced center to center timing sets can be necessary if the main bearing bores are align bored. This is another reason NOT to align bore an engine unless ABSOUTELY necessary, and I doubt if one in ten actually needs to be align bored, but a lot of machine shops just do it automatically without bothering to actually measure alignment with a machinist's bar and .0015" feeler gage, which is about a two-minute job.

Watch-out!!!

Duke

[Kenneth H.]

Re: Timing chain and gear for 1970 LT1

Duke, thanks for the info. My head was spinning with all of the different options. I spoke to Cloyes and they confirmed that the 9-3100 could cause the problem that you discussed concerning the timing cover. I also need the gear, so the NAPA NTP 9163 won't solve the problem since that part number includes only the timing chain. NAPA carries the C3023X but not the C3023K but according to Cloyes either will work. The C3023X has an adjustment to fit three different applications making it kind of a "generic" timing set but otherwise is the same as the C3023K.

[Joe L.]

Re: Timing chain and gear for 1970 LT1

Duke, thanks for the info. My head was spinning with all of the different options. I spoke to Cloyes and they confirmed that the 9-3100 could cause the problem that you discussed concerning the timing cover. I also need the gear, so the NAPA NTP 9163 won't solve the problem since that part number includes only the timing chain. NAPA carries the C3023X but not the C3023K but according to Cloyes either will work. The C3023X has an adjustment to fit three different applications making it kind of a "generic" timing set but otherwise is the same as the C3023K.

Ken------


I use only the Cloyes 9-3100 for small blocks and have done so for years. This is an absolutely bullet-proof timing set that uses a very high quality Renolds chain. Yes, it does cost much more than the stock-replacement or other generic timing sets but, as with most things, you get what you pay for.

All 1966-91 Corvette small blocks used a Morse-type chain with a nylon-toothed, aluminum cam sprocket and powder metal crank sprocket. However, the nylon-toothed cam sprockets were discontinued from GM SERVICE a very long time ago and replaced by a cast iron sprocket, even while the nylon-toothed sprockets continued to be used for PRODUCTION.

A stock-type chain with cast iron sprocket is OK; there are millions of them out there working just fine. But, not for me. For me it's Cloyes 9-3100. Every time.

By the way, I should have noted that I have used the Cloyes 9-3100 with the exact same timing cover you have on your 1970 LT-1 and I've never had any sort of interference problem, at all. I have heard of some folks having a problem with very slight interference with the cam sprocket/timing chain and block. However, I've never had this problem, either. If it were a problem, very minor grinding of the block surface will cure it.

[Duke W.]

Re: Timing chain and gear for 1970 LT1

Duke, thanks for the info. My head was spinning with all of the different options. I spoke to Cloyes and they confirmed that the 9-3100 could cause the problem that you discussed concerning the timing cover. I also need the gear, so the NAPA NTP 9163 won't solve the problem since that part number includes only the timing chain. NAPA carries the C3023X but not the C3023K but according to Cloyes either will work. The C3023X has an adjustment to fit three different applications making it kind of a "generic" timing set but otherwise is the same as the C3023K.

It appears that NAPA has rearranged how the timing sets are sold and you now buy the two sprockets and chain separately under their NAPA Timing Products brand. That was the way it was with GMPD. You should always replace the complete set - the chain and both sprockets.

Also, my notes on the Cloyes K and X were wrong. Sorry. As you said, the K is the OE replacement truck roller set, and the X is the same other than having a crank sprocket with three keyways to allow OE indexing of the cam or plus or minus four degrees. I don't recommend changing indexing of the LT-1 cam on a 350, so the K is what you need, and it's 16 bucks at O'Reillys. That's for the complete set!

I know Joe likes the 9-3100, but at four to five times the price, I don't see a benefit. The early wide silent chain and truck roller chain were bulletproof - even in racing engines. OE timing chains got a bad reputation due to the nylon sprocket, but it's long gone and the current silent chain replacements have cast iron sprockets.

I've never heard of an OE timing chain system failing other than the ill-fated nylon sprocket, but chains do wear, which can upset valve and spark timing due to slack in the chain. With reasonable oil change intervals silent chain wear should not be an issue until at least 100K miles and at least 150K miles with the roller set, which is why I recommend the roller set. It's more durable. The early wide silent chain set I replaced on my '63 327/340 with same from GMPD at 115K miles had no significant wear, and of course, I maintained the engine very well with frequent oil changes.

Dirty oil is what wears timing chains.

Duke

[Kenn S.]

Re: Timing chain and gear for 1970 LT1

Interesting discussion. I'm building an L-48 now, so it's timely (no pun intended).

I was also taught to drill a small (1/32") hole in the center galley cap that allows oil to flow from the cam galley to the upper sprocket. Of course you do this prior to installing the plug.

The hole isn't big enough to noticeably drop pressure in the cam galley, but allows just a bit of oil to spray onto the upper sprocket, lubricating the entire chain. I've run this on several Corvette high-perf engines with no detrimental effects (oil pressure, cam lube, etc.). Just be sure you seat and lock the plug properly, which you should do anyway.

[Kenneth H.]

Re: Timing chain and gear for 1970 LT1

Duke and Joe, thanks for the info. Based on the discussion, it seems to me that all three timing sets (9-3100, C3023K and C3023X) will work for my application and it just comes down to my comfort level with the cost of the timing set.

Thanks again for your help.

[Joe L.]

Re: Timing chain and gear for 1970 LT1

Duke and Joe, thanks for the info. Based on the discussion, it seems to me that all three timing sets (9-3100, C3023K and C3023X) will work for my application and it just comes down to my comfort level with the cost of the timing set.

Thanks again for your help.

Ken------


Pretty much. The other timing sets will be adequate; I've never indicated that they would not be. However, the 9-3100 is an extremely high quality timing set and the best one out there. There is a reason that it costs about 5 times as much as the others and it's definitely not just additional mark-up.

[Duke W.]

Re: Timing chain and gear for 1970 LT1

I think the reason the C-3023K is so inexpensive is that it is a very high volume item. The "X" version is nearly twice the price, and the only difference is the two extra keyways on the crankshaft sprocket to allow 4 degrees camshaft advance or retard.

That's one of the great things about Corvette engines. They are very inexpensive to rebuild because they use many internal parts that are common to the ten plus million Gen I small blocks that GM built. There a still millions in service and an original design objective was low cost.

A similar vintage Porsche 911 rebuild is probably in the $15-20K ballpark. A Colombo-based Ferrari V-12 about double, and a Lampredi-based V-12 is just plain outa sight.

Duke

[Terry M.]

Re: Timing chain and gear for 1970 LT1

I think the reason the C-3023K is so inexpensive is that it is a very high volume item. The "X" version is nearly twice the price, and the only difference is the two extra keyways on the crankshaft sprocket to allow 4 degrees camshaft advance or retard.

That's one of the great things about Corvette engines. They are very inexpensive to rebuild because they use many internal parts that are common to the ten plus million Gen I small blocks that GM built. There a still millions in service and an original design objective was low cost.

A similar vintage Porsche 911 rebuild is probably in the $15-20K ballpark. A Colombo-based Ferrari V-12 about double, and a Lampredi-based V-12 is just plain outa sight.

Duke

10+ Million small blocks Duke? Flint engine claimed 59 million small blocks when they closed that plant. I have no idea how many were built by Tonawanda not to mention McKinnon and Mexico. Lots of pluses there.

[Duke W.]

Re: Timing chain and gear for 1970 LT1

Thanks for the correction. I was figuring half a million for 20 years, but it was really more like a million plus average for nearly 50 years in production cars/trucks, and they are still being produced for over-the-counter. I think that back in the sixties, Chevrolet Division alone built something on the order of two million cars and light trucks annually, about half of GM total production, most of which had small blocks.

So I'll try to remember "over 60 million". There are probably at least 10 million still in service - cars, trucks, marine, and industrial.

Duke