cam lobes pitted

TSwede · 05-31-2002, 01:35 PM

I've got my engine in bits at the moment as some of you are aware - nearly done everything but noticed that some of the cam lobes are pitted - there is hardly any ridge on the edge of the lobes so they seem to have lots of life left so why have they pitted -

The big question is do they need replacing - I've spent so much on the rest of the engine that I really can't spend anymore at the moment...

Can I replace them some other time?

Will they last long if I put them back or will they explode in a puff of smoke?

I'm supposed to be putting the heads back together this weekend so any advice would be most helpful...

I wasn't expecting this...... bugger!!!

Swede

scca_ita · 05-31-2002, 01:44 PM

I have been told that pitted cam lobes are BAD. Dont regrind just replace.

TSwede · 05-31-2002, 01:46 PM

Anybody know how bad????

An why... I've heard they can be reground but I was just going to put it back on as is.

Joeaksa · 05-31-2002, 01:54 PM

Saw some postings years back where certain oils would cause this...

Joe

Early_S_Man · 05-31-2002, 01:56 PM

What is the span of the largest of the pits ... 1 mm, 2 mm, or larger?

You ought to talk to Web-Cam ... and see what they recommend. I believe the pitted cams can be reground and have satisfactory durability. Their 20/21 grind is what you would want for your CIS engine, and it is about $350 for a regrind.

TSwede · 05-31-2002, 01:58 PM

I'll measure up and post back in a minute - the thing is I'm in the UK so if anyone knows anywhere good in the UK that does this sort of thing..

Superman · 05-31-2002, 01:58 PM

If you have not already done so, you should drill out the small aluminum plugs and remove the spray bars in the heads. These spray oil onto the valve train. They are probably filled with cruddies. That's a technical term.

If I were in your situation and I could not afford cams, I would put them back in and begin saving.

john walker's workshop · 05-31-2002, 02:07 PM

i've seen a lot of minor pitting on SC cams. there doesn't seem to be any problem continuing to run them. they never wear the lobe out unless there's an oiling problem, and the pits basically just hold oil. i wouldn't be too concerned.

TSwede · 05-31-2002, 02:12 PM

I'll put them back in for now, the pitting is mostly away from the surface that contacts the rocker - mostly it's at the edges.... one area is quite bad and impinges on the rocker artea but it will run OK because it's at one edge - the main contact area on all lobes is smooth...

TSwede · 05-31-2002, 02:14 PM

Are there any other cams that fit this in case I see any good used engine bits in the future etc etc - I know the 2.7 isn't the same as the S but was wondering about others..

Peterfrans · 05-31-2002, 02:22 PM

/
I also had pitting on my original cams. I just replaced them. I still have the cams in my garage as they are early s cams.

I think you should be able to source used items for less than the cost of a regrind, at least here in europe.

I drilled the plugs from the spray bars but found no crud. Still puzzled why they were pitted.

I have two used cams lying around which I bought in a lot of ebay. I believe them to be 2.7 cams. Is there an easy way to identify them?

silverc4s · silverc4s's Garage

I have had scored and pitted S cams built up, reground and re hardened, by WebCams, if I remember properly. I do not have a lot of miles on them so I can't attest to their durability, but the work was done through a recommendation of German Precision in Sunnyvale, CA - a highly respected Porsche machine shop

If they are OEM Porsche cams, I would say go ahead, if they are not, they may be paperweights.

The secret is in the hardening after rework I think. Mine looked kind of Parkerized, then the lobes were polished when I got them back..
Regards,

TSwede · 05-31-2002, 02:24 PM

Carquip has a homepage with a table of cams and part numbers on it....

TSwede · 05-31-2002, 02:26 PM

in the UK who can do this.... also, how much did it cost you if you don't mind me asking?

silverc4s · silverc4s's Garage

BTW, the cause of death of my engine was prolonged operation with low oil pressure, causing the entire valve train to wear itself out prematurely.... We had to replace all rockers, rocker shafts, valves, cam drive parts incl intermediate shaft, et cetera. It was a very sad day in my life...

silverc4s · silverc4s's Garage

I had the two cams done in 1995, for about $200 as I recall..

TSwede · 05-31-2002, 02:32 PM

I'll search round on the internet for a reputable looking company and price up the work - also secondhand an new cams before making my decision....

I started all this when i ended up with bent valves and one burn't out one... once I got started i ended up doing the whole bottom end as well.....

Snowball effect - and it hasn't finished yet.

silverc4s · silverc4s's Garage

I started all this when i ended up with bent valves and one burn't out one... once I got started i ended up doing the whole bottom end as well.....

I think we've all been there......

Doug Zielke · 05-31-2002, 02:45 PM

Bill (silverc4s),
A MH-900e is far from being a "dumb toy". You lucky bastarde!

TSwede · 05-31-2002, 02:49 PM

there are a few UK companies who do this type of work but god knows if they do it good bad or ugly!!!! I'll keep looking and hopefully I'll hear from someone in the UK who's had it done... I could always ship to the US but time is an issue...