Home » Public Forums » GMCnet » Roller Cam issue - please read if you have one.
| Roller Cam issue - please read if you have one. [message #150590] |
Thu, 24 November 2011 11:01  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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To all GMC people with roller follower cams, please be aware of this issue.
An owner has had a recent issue with an engine built and installed last year.
The engine was built with a Competition Cams 42-413-9 Roller cam kit.
It wore out the distributor drive gear in about six thousand miles. In a query to Competition Cams, he found out that they only expect five thousand miles of life from the bronze distributor drive gear.
If you have a Comp Cams Roller, carry a distributor drive gear and the tools to replace or a back-up distributor and plan to replace this gear on a regular basis.
Unfortunately, this owner only works the GMC-EFI group.
More information will be available as more is learned.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Roller Cam issue - please read if you have one. [message #150600 is a reply to message #150590] |
Thu, 24 November 2011 11:56  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Matt, the phophorous bronze distributor gear should only be used with a non
hardened cast camshaft. When you use a heat treated cam like the comp cams
roller, the proper distributor drive gear should be the mehinite one. It
has the appearance of steel, but is in fact cast iron that has been alloyed
and recast and is friction compatible with the hardened roller camshafts.
What your acquaintance with the bronze gear found out is that the two
materials are not compatible, and the distributor gear will wear
prematurely. Probably another case for reluctor wheels and digital timed
ignitions with crank position sensors instead of distributors. Still need
the distributor shaft to drive the oil pump, though, but the oil pump is
not timed and if a bunch of slack shows up in the gear train, it is not as
bad of a problem, unless it strips out completely. If that happens and the
engine continued to run, bad stuff happens. Do not ask me how I gained this
knowledge, it is too painful to the wallet. It seems that when a person
modifies an engine, sometimes it sets up cascading failures that they did
not consider. BTDT myself. Everyone, Eat lots of turkey, take frequent
beverage breaks, and spend the day kicking back with your loved ones.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Thu, Nov 24, 2011 at 9:01 AM, Matt Colie <matt7323tze@gmail.com> wrote:
>
>
> To all GMC people with roller follower cams, please be aware of this issue.
> An owner has had a recent issue with an engine built and installed last
> year.
>
> The engine was built with a Competition Cams 42-413-9 Roller cam kit.
>
> It wore out the distributor drive gear in about six thousand miles. In a
> query to Competition Cams, he found out that they only expect five thousand
> miles of life from the bronze distributor drive gear.
>
> If you have a Comp Cams Roller, carry a distributor drive gear and the
> tools to replace or a back-up distributor and plan to replace this gear on
> a regular basis.
>
> Unfortunately, this owner only works the GMC-EFI group.
>
> More information will be available as more is learned.
>
> Matt
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will
> find
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
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| Re: [GMCnet] Roller Cam issue - please read if you have one. [message #150601 is a reply to message #150600] |
Thu, 24 November 2011 12:18 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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The particular cam that is being written about is a Comp Cam made of billet steel. Comp Cam indicates that the distributor gear must be a bronze gear or a synthetic plastic gear. It will chew up steel gears in no time and even cast iron gears with the graphite Mehinite process. Steel or cast iron gears on the distributor will also chew up the billet steel of the cam and then leave hardened steel particles in the engine.
Comp Cams have advised the GMCer that has that cam that the bronze gear is a sacrificial part and that the expected life is 5000 miles. Obviously that particular cam is meant for a dragster or race car which would be worked on after each race and not a GMC. It appears that the owner will have to ether change out the bronze gear every 5000 miles at a cost of $85.22 plus shipping from Comp Cams or else replace the cam with one with a pressed on cast gear if he wants to use a steel gear on the distributor.
On Nov 24, 2011, at 10:56 AM, James Hupy wrote:
> Matt, the phophorous bronze distributor gear should only be used with a non
> hardened cast camshaft. When you use a heat treated cam like the comp cams
> roller, the proper distributor drive gear should be the mehinite one. It
> has the appearance of steel, but is in fact cast iron that has been alloyed
> and recast and is friction compatible with the hardened roller camshafts.
> What your acquaintance with the bronze gear found out is that the two
> materials are not compatible, and the distributor gear will wear
> prematurely. Probably another case for reluctor wheels and digital timed
> ignitions with crank position sensors instead of distributors. Still need
> the distributor shaft to drive the oil pump, though, but the oil pump is
> not timed and if a bunch of slack shows up in the gear train, it is not as
> bad of a problem, unless it strips out completely. If that happens and the
> engine continued to run, bad stuff happens. Do not ask me how I gained this
> knowledge, it is too painful to the wallet. It seems that when a person
> modifies an engine, sometimes it sets up cascading failures that they did
> not consider. BTDT myself. Everyone, Eat lots of turkey, take frequent
> beverage breaks, and spend the day kicking back with your loved ones.
> Jim Hupy
> Salem, OR
> 78 GMC Royale 403
>
> On Thu, Nov 24, 2011 at 9:01 AM, Matt Colie <matt7323tze@gmail.com> wrote:
>
>>
>>
>> To all GMC people with roller follower cams, please be aware of this issue.
>> An owner has had a recent issue with an engine built and installed last
>> year.
>>
>> The engine was built with a Competition Cams 42-413-9 Roller cam kit.
>>
>> It wore out the distributor drive gear in about six thousand miles. In a
>> query to Competition Cams, he found out that they only expect five thousand
>> miles of life from the bronze distributor drive gear.
>>
>> If you have a Comp Cams Roller, carry a distributor drive gear and the
>> tools to replace or a back-up distributor and plan to replace this gear on
>> a regular basis.
>>
>> Unfortunately, this owner only works the GMC-EFI group.
>>
>> More information will be available as more is learned.
>>
>> Matt
>>
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Roller Cam issue - please read if you have one. [message #150620 is a reply to message #150601] |
Thu, 24 November 2011 21:25 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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Jim Bounds just told me that he can supply a nitrate hardened gear which he says will solve the problem.
I don't know anything about that gear so please contact him for details.
Emery Stora
On Nov 24, 2011, at 11:18 AM, Emery Stora wrote:
> The particular cam that is being written about is a Comp Cam made of billet steel. Comp Cam indicates that the distributor gear must be a bronze gear or a synthetic plastic gear. It will chew up steel gears in no time and even cast iron gears with the graphite Mehinite process. Steel or cast iron gears on the distributor will also chew up the billet steel of the cam and then leave hardened steel particles in the engine.
>
> Comp Cams have advised the GMCer that has that cam that the bronze gear is a sacrificial part and that the expected life is 5000 miles. Obviously that particular cam is meant for a dragster or race car which would be worked on after each race and not a GMC. It appears that the owner will have to ether change out the bronze gear every 5000 miles at a cost of $85.22 plus shipping from Comp Cams or else replace the cam with one with a pressed on cast gear if he wants to use a steel gear on the distributor.
>
> On Nov 24, 2011, at 10:56 AM, James Hupy wrote:
>
>> Matt, the phophorous bronze distributor gear should only be used with a non
>> hardened cast camshaft. When you use a heat treated cam like the comp cams
>> roller, the proper distributor drive gear should be the mehinite one. It
>> has the appearance of steel, but is in fact cast iron that has been alloyed
>> and recast and is friction compatible with the hardened roller camshafts.
>> What your acquaintance with the bronze gear found out is that the two
>> materials are not compatible, and the distributor gear will wear
>> prematurely. Probably another case for reluctor wheels and digital timed
>> ignitions with crank position sensors instead of distributors. Still need
>> the distributor shaft to drive the oil pump, though, but the oil pump is
>> not timed and if a bunch of slack shows up in the gear train, it is not as
>> bad of a problem, unless it strips out completely. If that happens and the
>> engine continued to run, bad stuff happens. Do not ask me how I gained this
>> knowledge, it is too painful to the wallet. It seems that when a person
>> modifies an engine, sometimes it sets up cascading failures that they did
>> not consider. BTDT myself. Everyone, Eat lots of turkey, take frequent
>> beverage breaks, and spend the day kicking back with your loved ones.
>> Jim Hupy
>> Salem, OR
>> 78 GMC Royale 403
>>
>> On Thu, Nov 24, 2011 at 9:01 AM, Matt Colie <matt7323tze@gmail.com> wrote:
>>
>>>
>>>
>>> To all GMC people with roller follower cams, please be aware of this issue.
>>> An owner has had a recent issue with an engine built and installed last
>>> year.
>>>
>>> The engine was built with a Competition Cams 42-413-9 Roller cam kit.
>>>
>>> It wore out the distributor drive gear in about six thousand miles. In a
>>> query to Competition Cams, he found out that they only expect five thousand
>>> miles of life from the bronze distributor drive gear.
>>>
>>> If you have a Comp Cams Roller, carry a distributor drive gear and the
>>> tools to replace or a back-up distributor and plan to replace this gear on
>>> a regular basis.
>>>
>>> Unfortunately, this owner only works the GMC-EFI group.
>>>
>>> More information will be available as more is learned.
>>>
>>> Matt
>>>
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