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.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

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.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

That's interesting.......

The slack in the chain disappears when it's running...

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

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.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

By "Most," I meant most engines in general, not specifically slant sixes.

I wonder if chain technology has changed, or what?

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

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.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

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.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

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

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'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

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.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

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.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

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?

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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.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

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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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair