Stripped cam gear
- John Brooks
- 356 Fan
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Re: Stripped cam gear
I think the cam is broken...... Rotates until the closes lobe has pressure on it the it slips and binds, the realigns when rotated backwards, it broke the gear when the cam bound, crank kept turning from the flywheel momemtem. I had one like this in the late 60's broke right at the flange behind behind the gear.
John Brooks
62 Roadster
66 912
84 Cab
getting pushed around in porsches since 1965
62 Roadster
66 912
84 Cab
getting pushed around in porsches since 1965
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- 356 Fan
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- Joined: Wed May 21, 2008 9:15 am
Re: Stripped cam gear
Thanks John
Will know soon enough and will post a photo
Bummer. Dema Elgin modified it for my engine
Will know soon enough and will post a photo
Bummer. Dema Elgin modified it for my engine
- mario musto
- 356 Fan
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- Location: San Mateo Co. Calif.
Re: Stripped cam gear
Looks like the cam breaking boss in last photo in post #27 is cracked, and if so could be caused by broken cam.
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- 356 Fan
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Re: Stripped cam gear
Finished tear down. Cam hitting described above was operator error. Since cam gear was off, cam was interfering with crank.
Looks like cause was weak split cam gear, high spring pressure and probably high rpm excursion.
I will thoroughly clean and reassemble, using non-split cam gear. May also re-spring the valves.
I appreciate the comments from the members.
Thank you!
Mark
Looks like cause was weak split cam gear, high spring pressure and probably high rpm excursion.
I will thoroughly clean and reassemble, using non-split cam gear. May also re-spring the valves.
I appreciate the comments from the members.
Thank you!
Mark
- Harlan Halsey
- 356 Fan
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Re: Stripped cam gear
I would check with Dema Elgin regarding valve springs since it is his cam.
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- 356 Fan
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Re: Stripped cam gear
I am assembling parts for the engine re-build. Cam was a tiny bit pitted on one lobe, so I had Dema Elgin fix it up and re-grind the lifters.
Walt convinced me the double springs are not adding too much pressure and are more for control of harmonics.
Thinking about a straight cut steel cam gear set. On a thread from a few years ago, the input was they are not too noisy.
Are the 356/912 gears same as VW Type 1? Therefore widely available. Any set better than others?
Looks like a VW cam gear set is about 20% of the price of just a Porsche replacement gear (of course)
Thanks
Mark
Walt convinced me the double springs are not adding too much pressure and are more for control of harmonics.
Thinking about a straight cut steel cam gear set. On a thread from a few years ago, the input was they are not too noisy.
Are the 356/912 gears same as VW Type 1? Therefore widely available. Any set better than others?
Looks like a VW cam gear set is about 20% of the price of just a Porsche replacement gear (of course)
Thanks
Mark
- Martin Benade
- 356 Fan
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Re: Stripped cam gear
The post 1961? Vw gears would have to be used as a pair as the gear angle was changed. The cam gear wouldn’t have dowel pin holes, and originally would have been riveted to the cam.
Does anybody know if the straight cut gears make a pleasant whine, somewhat 911 ish, or do they just make plain old noise?
Does anybody know if the straight cut gears make a pleasant whine, somewhat 911 ish, or do they just make plain old noise?
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna
62 Cabriolet
56 VW
02 IS 300
04 Sienna
- Ron LaDow
- 356 Fan
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Re: Stripped cam gear
Dunno about the noise level, but the wear is probably 3X what the helical gear sees, with the resultant errors in cam timing.Martin Benade wrote: ↑Wed Dec 18, 2019 10:38 pm [...]
Does anybody know if the straight cut gears make a pleasant whine, somewhat 911 ish, or do they just make plain old noise?
Helical gears have the disadvantage of imparting an axial load on the driven shaft (cam, here); the vector of the helix angle. But they engage some number of teeth greater than one, so the load is spread and wear is reduced by (that guess above).
The 616 engine seems to ignore the axial load on the cam, and I've never seen any (documented) claim that the straight-cut gears add anything other than that noise.
To draw an analogy, there are folks who swear the intake roar from sparrow-strainer air cleaners must mean more power; I'm waiting for the evidence.
Ron LaDow
www.precisionmatters.biz
www.precisionmatters.biz
- Harlan Halsey
- 356 Fan
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Re: Stripped cam gear
A few years ago I was Pitted across from Bob Kahn. He started the engine in his Speedster, and the racket was so bad that alarmed,I ran across and said shut it down. Bob yelled not to worry, that was the sound of the straight cut cam gears!
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- 356 Fan
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Re: Stripped cam gear
My friend had his engine stop on the way home from North South, the engine is now at Jacques's and it has been torn down, the only failure seems to b the cam gear loosing a bunch of teeth. Any ideas on what happened ?
The engine is a Stoddard exchange rebuild, 912, with maybe 25,000 miles. .
The engine is a Stoddard exchange rebuild, 912, with maybe 25,000 miles. .
- C J Murray
- 356 Fan
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Re: Stripped cam gear
What does Jacques think?
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'59 Sunroof
'60 Devin D Porsche Race Car
'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
'09 Smart Passion
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- 356 Fan
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Re: Stripped cam gear
He is puzzled too. He said he hasn't seen one this bad without a lot of damage to other parts. The case is off being cleaned maybe then the gear size can be measured. It was a -2 gear that failed.
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- 356 Fan
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Re: Stripped cam gear
The crank said "Go" and the cam said "NO"
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- 356 Fan
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Re: Stripped cam gear
A washer or a weak tooth on the cam gear are possible causes.
- mario musto
- 356 Fan
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- Location: San Mateo Co. Calif.
Re: Stripped cam gear
How does the steel gear on crank look? Did cam rotate freely with gear off and no other foreign items found in case?