Cam Wear

satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Cam Wear

Post by satterley_sr »

Just discoverd the cause of low power ( really low, about 35 hp on the dyno). Turns out the valves are only opening about .150". haven't cracked it open but I'm thinking the cam is worn. Probably only has about two seasons on it. We always used Mobil 1 synthetic street oil. Now I'm questioning whether the amount of zinc is adequate. But could also be a bad heat treat on the Elgin cam.

Dave DDC Racing
BobShedd
Posts: 57
Joined: July 16th, 2006, 10:34 am

Re: Cam Wear

Post by BobShedd »

I'd bet on it being the oil. With our solid lifer engines ( aka flat tappet ) we HAVE to use a racing oil ( Red Line, Royal Purple, Brad Penn ) or the " not street legal" Valovine oils. Street oils just dont have near enough ZDDP to keep the cams from wearing out very quickly. If you insist on using street oil then use one of the additives ( Comp Cams, Red Line, etc. ). On a V-8 with dual springs I have heard of the cam being destroyed before the dyno pulls were done. This applies to our classic cars and muscle cars - if they don't have roller lifters use racing oil.
Bob
Dave
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Joined: June 24th, 2006, 2:40 pm

Re: Cam Wear

Post by Dave »

I would guess you replaced the cam or lifters at your last rebuild. They were mis-matched . Wore the lobes of the cam.

Dave
satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

No, same cam & lifters at the re-build.
brian
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Joined: June 26th, 2006, 12:31 pm

Re: Cam Wear

Post by brian »

quite frankly, I don't consider our engines radical enough to expect failure from a lack of zinc. I agree that zinc is critical for flat tappet motors, but our spring rates and cam ramps are not radical enough to cause a problem. Does one think that all the stock VW's out there on the streets will have to run illegal off road oil? I don't think so.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
tiagosantos
Posts: 391
Joined: June 20th, 2010, 12:10 am

Re: Cam Wear

Post by tiagosantos »

Brian, don't most vees run slightly stiffer valve springs? Not sure if it would make any significant difference anyway. A lot of the local vees use cheap dino street oil and they seem to have no major trouble with that, changing it every race weekend.. I do use synthetic oil with zinc and whatever, but I don't think it's as big a deal as it may sound :)
hardingfv32-1
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Joined: December 1st, 2006, 8:01 pm

Re: Cam Wear

Post by hardingfv32-1 »

1) The springs are maybe 25-30% stiffer, but still extremely soft compared most race engines.

2) There is just a number of things that might cause a failure. Poor quality metallurgy of the cam core, poor heat treatment, maybe mismatching the lifts to the lobes during rebuild. Most of these things will not cause a failure, but a little bad luck and you have a problem.

Brian
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Cam Wear

Post by SR Racing »

A stock VW spring is about 50l#'s at closed height. A race prepped engine is close to 100#'s. And the rate is higher so at 1/2 open it is probalby double the stock spring. The stock VW saw 2300 rpm at points. We see close to 3500 at points and are always above 2500. (7000/5000 crank.) VWAC's for the most part were popular long before zinc was removed from the oil. We do a lot of engines for street VW's and most of those guys add ZDDP or use an off the road oil. USUALLY after a cam is broken in you can get by fie with the low levels zinc in current street oils. I would NEVER use a low zinc oil on an engine with a new cam/lifters. We also never use anything but high zinc oils in our race engines (new or old cam.)
A few years ago when the first low zinc oils were introduced there was a rash of cam failures. Both OEM and aftermarket. This was all over the automotive press. The cam builders we blamed, the owners were blamed, etc. Finally it was realized by all that the lack of zinc was the issue. This was heavilly publisized. Luckily most manufactures had converted to rollers or roller tips etc. And of course most engines were in daily drivers and/or had been broken in with high zinc oils. ZDDP additive is cheap and race oils are not a big part of your racing budget. Zinc also offers other advantages. It make no sense to use a street oil.
brian
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Joined: June 26th, 2006, 12:31 pm

Re: Cam Wear

Post by brian »

Jim's completely right and I do recommend zinc, especially on break in. Every magazine on the planet got on the zinc band wagon for a while. I understand using zinc on a street motor will kill a catalytic converter. While vee spring pressures are double, they are still much much lower than even latest generation and V8 motors. A more likely culprit in vee cam failure in an existing motor would be worn lifters, improper clearance and over revving the motor causing bounce in the components.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

http://www.flickr.com/photos/64167598@N03/5843077641/

Cam wear is severe

http://www.flickr.com/photos/64167598@N03/5843622472/

Lifters show very slight pitting

I talked to Elgin he is going to check the lifters for hardness & crown.

dave
satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

F Y I

Elgin checked out my worn cam & lifters. He said my lifters were soft, about 35 Rc. Said thats about what the cams are for hardness. Lifters should be approx 50 Rc. So I've got two new (re-ground) cams and two sets of new lifters . Two engines to re-build.

Dave
satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

Hate to bring this up again. But FYI. Doing a customer's engine with low power. Built by a west coast builder. .200 lift at the valve. Took it apart and lifters look great, Elgin cam is worn, this is after 1 week-end. Customer used Mobil 1. Possibly low ZDDP cause? Bad batch of cams (it was built about the same timeframe as when I had two failures)? Just damn frustrating.
I'll put in a new cam & lifters and have him use Redline Racing.
racing stuff
Posts: 34
Joined: January 30th, 2010, 11:08 am

Re: Cam Wear

Post by racing stuff »

We stock RedLine here in SE michigan and have seen an increase in sales of their "racing" weights, ever since it became known there is a "zinc" issue, particularly for those with "older style" racing engines.
Last edited by racing stuff on June 22nd, 2013, 12:08 pm, edited 1 time in total.
Keith
Averill Racing Stuff, Inc.
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http://www.racing-stuff.com
hardingfv32-1
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Joined: December 1st, 2006, 8:01 pm

Re: Cam Wear

Post by hardingfv32-1 »

Nothing to the bad batch theory. Elgin grinds the cores that are provided which cam come from anytime period or manufacture. The grinding process has not changed in decades.

I had a newly ground Elgin cam go bad in two weekends. The core was a new Brazilian cam. New lifters and both cam & lifter surfaces polished. 40w racing oil. The lifters on the bad lobe were scratched, but still had their curved surface profile, so I think it was a cam failure. The cams are not heat treated by Elgin. It could introduce warping along the cam axis. The cam bearing surfaces can not be ground to correct possible warping. There are no undersize cam bearings. The Elgin cams do get a post grinding surface (wear) treatment. At this point I would say that the heat treatment of the core cams have variable heat treatment depth between units/manufactures and the regrind sometimes penetrates the heat treatment zone.

Brian
satterley_sr
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Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

Brian,

So you think there is no solution to this problem? You just pay your money & takes your chance, eventually you will get a good one? Have you or anyone tried the Web cam Vee grind?

Thanks

Dave
Dietmar
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Re: Cam Wear

Post by Dietmar »

Dave:

ONLY cam I ever lost ( and I do not use any special break-in oil) was a Web grind- having said that, I was also using a two piece lifter and they were not compatible with the cam.
This was over 30 years ago.

I am VERY careful when I remove lifters from an engine- being sure they go back into the same hole. If I reface the lifters ( which I will ONLY do on original VW lifters) I chuck them in the lathe and test the hardness with a file. I do not have a hardness testing guage. If the file does not scratch the edge of the lifter, it has proven to have retained its hardness. If I can file the lifter, I throw it away.

Hope this helps.
Dietmar
http://www.quixoteracing.com
satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

Dietmar,

This might be your second, the story on this engine was it was built by you and brought to NY and then bought by my customer. It was never run until last month. It has dark pink valve covers.

Dave
hardingfv32-1
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Joined: December 1st, 2006, 8:01 pm

Re: Cam Wear

Post by hardingfv32-1 »

satterley_sr wrote:So you think there is no solution to this problem? You just pay your money & takes your chance, eventually you will get a good one? Have you or anyone tried the Web cam Vee grind?
IF... my theory about hardness depth is correct, then it would not matter who ground the cam. I am personally going to restrict regrinds to VW cores in the 'hope' that they have deeper heat treatment levels.

Brian
hardingfv32-1
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Re: Cam Wear

Post by hardingfv32-1 »

Dietmar wrote:.... I was also using a two piece lifter and they were not compatible with the cam.

Dietmar
I have heard this compatibility issue discussed before, but have doubts about its validity. What is your understanding of the topic? The cam and lifter hardness have to be similar or different hardness?

Brian
satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

I've got two worn cams, I'll check on their source. On one failure, Elgin told me my lifters were soft. I guess the theory is they would generate debris and the debris would wear the cam (my theory). From my GM transmission design days, we got abnormal wear if either part was drastically different in hardness.

Dave Satterley
Dietmar
Site Admin
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Re: Cam Wear

Post by Dietmar »

Dave:

I would really like to learn more about this engine that has my name on it - where is came from, when it was rebuilt and what the person did to start up an engine that has been sitting for who knows how long.

Any info you could provide would be appreciated. You have my address.

Dietmar
http://www.quixoteracing.com
brian
Posts: 1348
Joined: June 26th, 2006, 12:31 pm

Re: Cam Wear

Post by brian »

You mentioned your cams were worn and mentioned earlier a low messurement on the valve spring. Would you mind sharing the max lift on the worn cams?
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
satterley_sr
Posts: 237
Joined: June 27th, 2006, 3:27 pm

Re: Cam Wear

Post by satterley_sr »

Dietmar,

I will ask customer to get you info.

Brian,

Lift was approx .2 inch

Dave
hardingfv32-1
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Re: Cam Wear

Post by hardingfv32-1 »

In my case I would say that the intake cam lobe wore .100 in about 1.5 hrs. Won the previous race/session and progressively slow the whole next race weekend.

Brian
hardingfv32-1
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Re: Cam Wear

Post by hardingfv32-1 »

satterley_sr wrote:I've From my GM transmission design days, we got abnormal wear if either part was drastically different in hardness.
Dave Satterley
In the case of piston rings and cylinder walls, you need different hardnesses. You can not run chrome rings on chrome cylinder walls. The rings have to be softer in this example.

Relative to your statement, how much difference can you have using say the Rockwell C scale?

Brian
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