Camshaft Pitting- How much is too much?

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aTinBend
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Camshaft Pitting- How much is too much?

Post by aTinBend » Tue Sep 10, 2019 2:43 pm

1921 Center door sedan. Motor was last rebuilt 1959, but low miles since (<300 miles since) and stored with fresh oil for many years. Rest of car was recently restored. Motor had been running beautify. smooth idle, no weird noises, or vibration. Thus decision was made to leave motor alone other than pulling head, cleaning carbon, and fresh oil.

However, during road testing. Magneto quit unexpectedly and discovered magneto brass screw failures resulting in two plates floating around. Thank goodness caught problem before any damage was done. Of course, had to pull motor due to fix magneto. During inspection of transmission, gearing and other transmission parts, (bushings, clutch plates, drums etc) were in amazing condition.

Inspecting motor for due diligence while it is out. Motor extremely clean inside. Some carbon in the sump, but no metal bits in pan, Crankshaft looks great. No noticeable bearing run out, axial end play only .005". Con rods, pistons look good. cylinder walls very good. The only issue seen was pitting of the cams shaft. Worst was intake and exhaust on #3 but #4 as well, Number 1 & 2 also have some pitting but much less. See photos:
F- #3 Intake.JPG
G- #4 Intake.JPG
If this was a daily driver, I know the answer as to how much pitting is too much. But car will be parade car with only limited driving < 100 / year. Is this amount of pitting worth pulling / replacing cam / lifters etc. or should I take "it ain't broke, so don't fix it" approach". I am on the fence. Looking for second, (3rd,4th...347th) opinion ;) .

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dobro1956
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Re: Camshaft Pitting- How much is too much?

Post by dobro1956 » Tue Sep 10, 2019 3:12 pm

I vote for leave it alone. From your description of the engine, how it ran before, and how you plan on using it. I think it would be a waste of money to replace the cam. If you were doing a complete overhaul at this time I would vote to change it, but now is not the time in my opinion. There is very, very, very, (yes three vary's) little chance of the pits causing any kind of catastrophic failure. It may wear a little faster, but it will last a long time as-is. put her back together, and go for a drive :)


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Re: Camshaft Pitting- How much is too much?

Post by Les Schubert » Tue Sep 10, 2019 4:50 pm

It probably has 2 piece valves. They keep turning up as a serious problem by breaking. If you have the 2 piece valves, then I m going to vote to change them AND the cam (and probably the lifters). Lots of guys probably have lots of better cams laying on the shelf that they don’t plan to use, so maybe you can get one for a great price!
Consider that you may decide to drive it more!


myersair
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Re: Camshaft Pitting- How much is too much?

Post by myersair » Thu Sep 12, 2019 4:13 pm

I can only comment on what I've seen in aircraft engines.... I have done several aircraft engine teardown and overhauls and seen where cam lobes were worn completely off causing serious performance issues. I've also witnessed cam lobes partially worn down causing HP losses. All these cam lobe issues started with either a pitted lobe or pits in the lifter body. Long story short, If that cam shaft were in an airplane engine it wouldn't last 10 hours.

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Re: Camshaft Pitting- How much is too much?

Post by tinman080 » Thu Sep 12, 2019 4:46 pm

A combination of low valve spring pressure, low engine RPM and low operational mileage adds up to make any cam replacement not really necessary, unless the lobes are worn down badly. If the engine runs good I'd take my chances with the valves and let it all ride. My 2 cents worth. :D
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Ed Baudoux
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Re: Camshaft Pitting- How much is too much?

Post by Ed Baudoux » Thu Sep 12, 2019 4:53 pm

That camshaft is junk. I would not run it.
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Re: Camshaft Pitting- How much is too much?

Post by Charlie B in N.J. » Thu Sep 12, 2019 5:46 pm

Sooner or later depending on useage that cam will eat the lifters. Run it but keep in front of your mind.
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Re: Camshaft Pitting- How much is too much?

Post by sscargo » Thu Sep 12, 2019 5:50 pm

the pitting looks to be pretty deep, at least over .oo5" not just a slight surface and it covers more than a small percentage of the lobe area. the oil film will certainly be compromised. I recommend replacement. Especially because you have the engine apart. there will be no better opportunity.

Mat

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Re: Camshaft Pitting- How much is too much?

Post by aTinBend » Thu Sep 12, 2019 6:08 pm

Double checked the valves, they appear to be of the newer style. They are not the original two piece design based on visual inspection using both the stem shape and the holes in the top method. Must have been replaced during the 1959 rebuild with the post 1926-7 style.

I agree if the engine were in aircraft service, racing, or any other daily driver situation, the cam, lifters and values would all be replaced. But in this case of a future of low miles and gentle usage, still on the fence.

So as far I see right now, the tally of opinions is: one for definitely junking the cam, two for leaving well enough alone, One leaning to replace the cam if valves are bad (they aren't), One leaning to replace the cam if it was in an airplane (it's not).

That's what I like about this forum. A diverse group of opinions. Could be 4-2 to replace or 2-1 to keep it, depending on how you score it!

Any other thoughts out there, still got plenty of room to get to 347 opinions.... :D

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Re: Camshaft Pitting- How much is too much?

Post by aTinBend » Thu Sep 12, 2019 6:11 pm

Oops...missed those last two while I was writing, one more for removing, one more for running...

Thanks again for all the opinions.


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Re: Camshaft Pitting- How much is too much?

Post by rgould1910 » Fri Sep 13, 2019 9:55 am

I vote for a new cam and valve job. Would also look hard at the springs and lifters. If no appreciable slop in the beatings, I'd install a new Stipe 250 (stock grind) cam. All that will make a noticeable improvement in performance. :P


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Re: Camshaft Pitting- How much is too much?

Post by KeithG » Fri Sep 13, 2019 12:50 pm

With so many original camshafts replaced over the past few years (Think Stipe and Chaffins higher performance cams), there have to be lots of good original cams sitting around that could probably be had for little to nothing. Those would be a big improvement over your pitted cam. JMHO

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