RC924

Less than 5000 miles ago my worn camshaft was reconditioned by stellite hard facing to all lobes and reground to standard ROW specs. All cam followers (tappet buckets) were surface ground flat and subsequently polished to #800 by progressively finer grades of wet/dry abrasive on a glass plate, as recommended by the reputable cam engineering shop who performed the work. They initially inserted the followers in an acid bath (or similar) and determined that they could be resurfaced and were not hard chrome plated.

Now I am not so sure. The cam was removed as it looked like the hard facing had worn on one prominent lobe. Upon further inspection there was visible signs of wear to other lobes as well, however 3 lobes appeared unscathed by examination with a magnifying lens. What concerned me the most was pitting on ALL the follower faces to a varying degree. Initially I assumed that the worn cam or chipped particles had caused pitting estimated at up to 0.010" (10 thou or 0.25mm) deep. Although it was not as severe there is also pitting on followers that correspond to cam lobes that appear good.

Since I am not a metallurgist I don`t know the cause but at this time it appears to me that the follower face is deteriorating through the surface layer. It then looks like the rough surface and/or particles are aggravating the cam lobe wear. At present I believe that the cam followers are not hard faced or surface hardened but am happy to be corrected on this.











The top picture gives an indication of the wear to all the cam followers. The close ups show the pitting or chipping to the faces, starting with the most severe. Followers in the last 2 pics although worn themselves had not yet caused any damage to the stellite on the cam lobes.

That is assuming that I have determined the progress of wear correctly using basic logic rather than much experience or expertise. And BTW, standard valve springs were fitted and seat pressure checked at 60 - 65 Lbs, definitely no coil bind, cam assembly lube was used, run in procedure followed, synthetic oil and filter changed at install and after break in period.

Can anyone help me here? A few specific answers would be very much appreciated, as would be any CONSTRUCTIVE comments or advice.

1. WTF is causing this?

2. What is the composition of the cam follower faces?

3. Can these cam followers be successfully refaced and is there any specific process or procedure?

4. Is there any compatibility issues running a stellite faced cam with these lifters?

5. Is there an economic source of new cam followers 046 109 311 or is an alternative aftermarket replacement available?

TIA,
Roger

Spidey944

have never seen those wear like that b4. ever. I will check your part number in the morning and see what my cost is. I paid about 75 each for my 951 followers IIRC. I would say that your followers are now JUNK. what is the machine shop who refaced them saying?

KuHL 951

Sorry but those are miles beyond redemption. You need a new set of lifters as well as finding out why they used stellite for the hard facing on the cam. For a compromised wear surface, stellite could be much too hard for lifters that have been surface ground removing the hardened face and sides from the factory. Personally I would use a stock cam and new lifters. The only other thing that could have contributed is improper oil with a very low ZDDP content. These cars need at least .11%-.14% ZDDP to control shear damage. The pitting is most likely pieces of the lifter pounded back into the surface by the harder cam. Be sure and flush your oil and oil passages very well as some of junk might very well be in your oil pan. Man that is the worst I've ever seen.

Jay W

I had wear like that on my cam followers on a 16 valve engine. Cams are a bit worn too. I had blockage of the oil drainback valve in the head which ended up reducing the amount of oil that was able to get to the top end of the engine. The cam chain tensioner pads wore really quickly too. I discovered it when I had the head redone because of a broken timing belt. When I got it together there was only a trickle of oil coming out of the oil passages to lube the cam and followers. Cleaned out the valve and the oil flows like a river. I ended up replacing the cam followers that looked like yours, about 10 of them. I think only the 16 valve engines and the 89+ model years 8 valve engines have that anti drainback valve but you could have other blockage or low oil pressure problems.

KuHL 951

All the 944 heads have that anti-drainback valve in the head. They can get plugged after machining the top of the head if the shop isn't aware of it. There are two different styles of valves, a press-in and screw in but I forget which is early or late. It's located near No.4 on the exhaust side of the mating surface with the cam tower.

RC924

Appreciate the replies guys.

Agree that these followers are now complete crap.
It seems clear that this is a more involved issue than simple wear as I have not seen lifters like that before either.

The cam originally had wear to some lobes and this was rebuilt and reground using stellite IIRC, along with the followers being refaced. This was at one of Australia`s leading cam grinding engineers. I`m not sure now, think I`ve blown over $500 and possibly have other damage to the bearings and crank too.

This is on a 924 that has quite good drainage, no drainback valves and ample oil flow to the top end. With the cam cover removed and engine idling it just pisses out oil. The oil pressure was still excellent up to the time of cam removal. No idea as to the individual properties of the oil but will look into that.

Not sure at all what to do now. The cam has been returned to the shop for repair but I don`t think I want to risk a new set of followers (about $80 each) on a questionable cam. Is there any known compatibility issues using hard faced cams on these cam followers?

The other option is a new billet cam from Integral Cams with new followers but theres another $1000.

Getting a sore head banging it on the wall!

Roger

Jay W

My 944S had a push in drainback valve. There is a set screw on the side of the block that I had to loosen first.

RC924, see if you can buy some used followers and cam tower assembly. Many people have extras laying around. I have about 6 sitting in a cam tower in my basement.

pjburges

KuHL 951 -- what is "ZDDP?"

KuHL 951

It's a phosphrous/zinc anti shear additive that has been in good oils for years. Due to more recent high mileage requirements and attempts at lower friction it has been reduced in most US oils to a point where damage has been reported. I use the Valvoline VR-1 Racing because they still have high concentrations of ZDDP and our engines are old. The best bet is to read a few of the links below. They have been posted in several threads looking for the Holy Grail of oils.

http://www.valvoline.com/products/VR...otor%20Oil.pdf
http://www.racingheadservice.com/Inf...ID=-1228096506
http://www.hotrod.com/pitstop/hrdp_0...ive/index.html
http://www.lnengineering.com/oil.html

Team SSR

There is no inherent problems with the welded cams - assuming proper surface finish, lobe taper, etc. Also the stock lifters will work fine on the surface. If the replacement lifters were reground (not enough 'hard' surface left), or dished to start with it will cause a problem. A very aggressive cam lobe and/or very wrong spring pressure will also cause these issues.