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Double roller timing set
https://slantsix.org/forum/viewtopic.php?t=15312		 Page 2 of 2
Author:  SlantSixDan [ Fri Dec 09, 2005 8:23 am ]
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Quote:
Only the industrial truck/combine/tug/forklift/etc... (the yellow engines) had factory roller timing chains. Most trucks didn't have them.
All 225s mounted in North American-made Dodge/Fargo trucks and vans were yellow from '63 through '69. That does not mean they were the heavy-duty 225-2 or the ultraheavy-duty 225-3, it just means they were installed in trucks. The standard-duty 225-1 engines got painted yellow when installed in trucks, and they did not have roller timing chains from the factory.
Author:  Matt Cramer [ Fri Dec 09, 2005 12:22 pm ]
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Many of the companies that sell inverted tooth chain for non-automotive applications insist that inverted tooth chains are more durable and retain their precision better when stretched than roller chain. Obviously, Bosch Rexroth isn't an unbiased source, but here's their claims about their line of inverted tooth chain:

http://www.boschrexroth.com/business_un ... chains.pdf

Ramsey, another inverted tooth chain company, claims that their chains stretch less than 1% after running them nonstop for two years. That's about the expected lifetime of a normal roller chain.

Most stock timing chains, of course, have issues with nylon sprockets. But I've got to wonder if the reason that double roller chain caught on was that it was originally easier and cheaper to get ahold of all-steel sprockets.
Author:  emsvitil [ Fri Dec 09, 2005 1:49 pm ]
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That's interesting.......

The slack in the chain disappears when it's running...
Author:  SlantSixDan [ Fri Dec 09, 2005 2:21 pm ]
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Quote:
Most stock timing chains, of course, have issues with nylon sprockets. But I've got to wonder if the reason that double roller chain caught on was that it was originally easier and cheaper to get ahold of all-steel sprockets.
Nope.

Remember, the nylon-over-aluminum camshaft sprocket wasn't put on the slant-6 until the 1972 model year. For the 12 model years prior to that, the standard-duty slant-6s had all-steel timing sprockets and inverted-tooth chains, while the heavy-duty slant-6s had all-steel timing sprockets and double-roller chains.
Author:  Matt Cramer [ Sat Dec 10, 2005 9:31 am ]
Post subject: 
By "Most," I meant most engines in general, not specifically slant sixes.

I wonder if chain technology has changed, or what?
Author:  SlantSixDan [ Sat Dec 10, 2005 10:07 am ]
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My cynical, skeptical guess based on what I see happening in virtually every other segment of the auto parts industry:

Chain technology hasn't changed a bit. What's changed is that now MBAs run the parts companies, instead of engineers, so whatever's cheapest out of China gets promoted as the one to pick.
Author:  Matt Cramer [ Mon Dec 12, 2005 12:24 pm ]
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I've mostly been looking at industrial supply sources for my info on the different types of chains. Usually with industrial work, there are more sources for roller chain and double roller chain than for inverted tooth chain. A couple of the catalogs here at work list prices for double roller chain by the foot, but I haven't looked at prices for inverted tooth chain.

With the inverted tooth chain companies, it seems they have some sort of arguement over who's come out with the latest and greatst replacement for pins. Which I suspect contains a fair amount of hype, of course, but these do appear to be new developments.
Author:  bwhitejr [ Tue Dec 13, 2005 9:39 am ]
Post subject:  Double Roller Timing Set
I bought a set this Summer from RockAuto.com

7/20/2005 Rock Auto S339 Cloyes (Crank Gear) $23.79
7/20/2005 Rock Auto C168 Cloyes (Chain) $12.86
7/20/2005 Rock Auto S338 Cloyes (Cam Gear) $46.79
7/20/2005 Rock Auto Shipping $13.34

Absolutely gorgeous!

bwhitejr
Author:  dakight [ Tue Dec 13, 2005 10:36 am ]
Post subject: 
Quote:
Most stock timing chains, of course, have issues with nylon sprockets. But I've got to wonder if the reason that double roller chain caught on was that it was originally easier and cheaper to get ahold of all-steel sprockets.
I think the main reason was the idea, whether true or not, that roller chains are subject to less friction and therefore increase available horsepower. That was the rationale I always heard but again, I don't know whether it is true or not and if true if it is significant.
Author:  Matt Cramer [ Tue Dec 13, 2005 11:10 am ]
Post subject: 
Quote:
I think the main reason was the idea, whether true or not, that roller chains are subject to less friction and therefore increase available horsepower. That was the rationale I always heard but again, I don't know whether it is true or not and if true if it is significant.
While that can sound reasonable, the friction losses are pretty much equal between the two. The teeth on an inverted tooth chain roll against the sprocket anyway - they don't scrape.

Now, if you were talking about some of the cheaper chains that look like roller chain but lack true rollers, you do have more friction.
Author:  440_Magnum [ Tue Dec 13, 2005 12:21 pm ]
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Quote:
From what I've learned about chains, if you can get a stock-type chain with all steel gears and have the gear teeth heat treated, the result can be at least as strong as a double roller chain.
Hey Matt,

I can tell you from personal experience that you can indeed run an all-steel gear set with a conventional "silent" chain practiaclly forever and it won't strip or break the way nylon teeth will... BUT it will stretch and timing will get VERY sloppy compared to a true roller set.

And while I'm at it, the non "true" roller chains aren't even as good as a conventional chain with steel gears, IMO.


As for the claims of greater precision with inverted tooth chains as they wear... that's interesting, and certainly NOT what I observe with a timing light on an idling engine with high miles on an inverted tooth chain compared to an engine with high miles on a true roller. I wonder if it has to do with the fact that the loading on an automotive timing chain is very "jerky" as the cam lobes operate?
Author:  Matt Cramer [ Wed Dec 14, 2005 5:52 am ]
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Thanks, Magnum. Glad to hear from someone who has a side by side comparison.

That wouldn't surprise me about the uneven loading on a camshaft. A worn inverted tooth chain is held steady by its tension, so if the loading is uneven it may start misbehaving.
Author:  Matt Cramer [ Wed Dec 14, 2005 2:02 pm ]
Post subject: 
Ok, I think I now see just what the issue is with an inverted tooth chain after taking another look at 440_Magnum's post and Bosch's illustration of how wear affects the inverted tooth chain. It's like I finally found a missing piece in a jigsaw puzzle.

The Bosch illustration assumes that the tension in the chain stays in the same direction. But a lifter pushing a valve closed would actually drive the camshaft forward. And when that happens, the cam sprocket can leap ahead by nearly a whole tooth width with an inverted tooth chain. The double roller doesn't allow nearly as much movement.

Looks like I'd been examining the wrong aspect of timing chain stretch.
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