| Cam sprocket - plastic or not? [message #365415] |
Tue, 13 July 2021 20:32  |
kwharland
Messages: 246
Registered: November 2005
Location: Central Florida
Karma: 0
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Soon to be new owner asked if timing set had been changed and if not, was the cam sprocket plastic or not and I could not answer.
1978 Eleganza II
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| Re: Cam sprocket - plastic or not? [message #365417 is a reply to message #365415] |
Tue, 13 July 2021 22:11  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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OE was nylon over aluminum cam gear. Heat and combustion by products attack the nylon over time. I’d be surprised to find a working survivor these days but possible.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Cam sprocket - plastic or not? [message #365443 is a reply to message #365415] |
Thu, 15 July 2021 07:57 |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
Karma: 1
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I second the mention using the Cloyes 9-3113 set (steel). We had our OEM nylon gear pulled a few years back by our mechanic, 65K miles on it, and the nylon gear was pristine believe it or not. However our worry was like others mentioned, not knowing how much life the nylon gear had left and didn't want to worry about it.
Chris
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
[Updated on: Thu, 15 July 2021 07:58] Report message to a moderator |
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| Re: Cam sprocket - plastic or not? [message #365478 is a reply to message #365415] |
Fri, 16 July 2021 17:57 |
Greg C.
Messages: 224
Registered: October 2019
Location: Knoxville, TN
Karma: 0
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At 67,000 miles, my gear looked good but the chain had stretched to the point that half of the crank gear teeth on the bottom were visible above the chain.
Greg Crawford
KM4ZCR
Knoxville, TN
"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags
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| [GMCnet] Re: Cam sprocket - plastic or not? [message #365479 is a reply to message #365478] |
Fri, 16 July 2021 19:09 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Stock or plastic makes no difference. It's the combination of wear between
gears, sprockets, and chains that gives you the slack that RETARDS CAM
TIMING, the effect is that the torque curve is moved upwards in RPM'S.
If your 403 won't pull the hat off your head at 2200 rpm, but runs
like a scalded dog at 3600+ RPM'S, you probably have a stretched timing
chain. New double roller chain and sprockets, advanced 4° or so will wake
the lower rpm range up.
Jim Hupy
Salem, Oregon
On Fri, Jul 16, 2021, 3:58 PM Greg Crawford
wrote:
> At 67,000 miles, my gear looked good but the chain had stretched to the
> point that half of the crank gear teeth on the bottom were visible above the
> chain.
> --
> Greg Crawford
> KM4ZCR
> Knoxville, TN
>
> "Ruby Sue"
> 1977 Royale
> Rear Bath
> 403 Engine
> American Eagle Wheels
> Early Version Alex Sirum Quad bags
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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