Stripped cam gear

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Mark Schumacher
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Stripped cam gear

#1 Post by Mark Schumacher »

Any ideas on what may cause this failure?
Engine is modified with dual valve springs.
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Tim Berardelli
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Re: Stripped cam gear

#2 Post by Tim Berardelli »

Mark,

More details, unless you enjoy wags! How many miles on the engine, any recent or last work prior to the gear taking a dump, the barrels look very "fresh". Hope you have a full flow oil filter, if not, you will need to dissemble to the last nut & bolt to find/remove the non-ferrous "pixie dust" that is everywhere in the engine.

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C J Murray
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Re: Stripped cam gear

#3 Post by C J Murray »

What do the cam lobes and lifters look like? Were the valves hitting the pistons? How radical is the cam and how much spring pressure were you using? Who made the gears? Is that a groove in the crank gear?
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Re: Stripped cam gear

#4 Post by David Jones »

I think I am stating the obvious here but it looks like the camshaft became the immovable object as the crank kept moving probably as a result of the car still being in gear. I will do a WAG that the valve gear is at fault, maybe a seized or bent valve or broken lifter jamming the camshaft.
Bigtime teardown and cleanup regardless.
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Chuck Allard
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Re: Stripped cam gear

#5 Post by Chuck Allard »

I've seen that on other grooved cam gears.

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Re: Stripped cam gear

#6 Post by Mark Schumacher »

Thanks the response:
- This is a 1883 engine with Shasta cast iron barrels/JE forged pistons. I built the engine about 5 yrs ago. Has maybe 12,000 miles. I run 2-3 DE events/yr so it sees RPM’s. Rev limiter set at 6200.
- cam is Elgin 7208. Dual springs because that’s what Walt Watson said I need when he built the heads. Full flow Canton-Mecca oil filter
- Have not yet pulled the sump to inspect cam lobes/lifters.
- Cam gears are stock Porsche far as I know. There is a groove in cam gear, not in crank gear
I do admit to driving the engine hard, but you’re supposed to drive a Porsche hard. Just trying to avoid the problem on the rebuild.

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Re: Stripped cam gear

#7 Post by Mark Schumacher »

The failure announced itself as what sounded like a valve leak. Car ran strong for a few miles.
Then stopped.
Yes, full rebuild ahead. I live in Minnesota and the winter is long.
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Re: Stripped cam gear

#8 Post by Vic Skirmants »

DON'T groove the cam gear! It only weakens it, and does not produce copious amounts of added horsepower.

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Re: Stripped cam gear

#9 Post by Mark Schumacher »

I am sure the groove was added or recommended by either a Competition Engineering or by the vendor of the engine parts. I am not smart enough to have come up with that mod myself

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Re: Stripped cam gear

#10 Post by Martin Benade »

Could that somehow have caused this failure, or is it just a waste of time for the three flypower it gained?
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Re: Stripped cam gear

#11 Post by C J Murray »

Yes it could have caused the failure. Continue to look for anything that could have been binding the camshaft also. Your cam does not require excessive spring pressure but call Dema Elgin to confirm that. If you want longevity you must use as little spring pressure as possible. Often a machinist will spec excessive spring pressure so that the parts don't bang into each other but a well designed cam can often work with stock springs.
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Re: Stripped cam gear

#12 Post by Mark Schumacher »

Dema was very helpful in specing this cam some yrs ago. Go to hear he is still active.
I will do more tear down and investigation in the next few weeks and will post results

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Re: Stripped cam gear

#13 Post by Don Gale »

Just curious, what does a grooved cam gear supposedly offer? Less contact friction, better tooth lubrication, trivial reduced rotating mass?
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Re: Stripped cam gear

#14 Post by David Jones »

F Vee engine builders did it supposedly to help oiling/lubrication of the gears and to channel away excess lubrication. Kind of catch 22 situation. Sometimes there are many conflicting stories on reasons for doing things. I thought it silly as the cam gear is soaked in oil.
I also question double valve springs. I can hit in excess of 6500 rpm with single springs and the right amount of valve spring shims. Extra seat pressure can easily result in tuliped valves which can break and make everything crater. The sound of a valve leak? before hand could have been a valve sizing in a guide.
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Re: Stripped cam gear

#15 Post by Ron LaDow »

Don Gale wrote: Sat Nov 09, 2019 9:31 pm Just curious, what does a grooved cam gear supposedly offer? Less contact friction, better tooth lubrication, trivial reduced rotating mass?
Supposedly relives trapped oil, but I really don't see an escape path.
To be honest, if you had spent many hours on a dyno and optimized everything else, it would be worth testing one. It wouldn't take long so you should have pretty good A-B comparisons.
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