atb

I'm curious what people have to say about this.

Any other motor you need to keep the used lifters matched with the cam lobes due to the wear patterns, or you can expect to have some serious premature wear on the your valve train.

I've heard of numerous cam swaps (myself included) where people have run the same lifters, and run used or reground cams on them without failure. Why is this?

When I build the stroker with the B1 cams, I'm going to bite the bullet and get new lifters, but that's because I can't fathom the idea of using used tappets in an otherwise brand new motor.

Let's here your opinions on this seemingly 928 anamoly.

BC

Beware, IIRC, new lifters. I have only heard of problems with quality/durability of new 2V lifters in both 944 and 951 forums, but serious problems no less.

Possible carry over into 32V lifters.

Advise.

over.

Vilhuer

Bullet might be smaller than you think. We are just looking into possible non OEM replacement part. It looks like certain BMW inline six engine lifters could be exact same size as 4 valve 928 parts. These are same style as ones used in S3 and some early S4 engines. Meaning they have oil groove on their side. If they are usable cost for replacement drops down to less than half compared to what it is now.

If I have understood correctly how lifters and cam interact one part of it is that cams rotate lifters around. This can be achieved by placing cam lobe slightly off center on top of lifter. This will force lifter to rotate and lessen its wear. I'm not sure if this is true or not but it could be one explanation why they seem to be so good even when cams have pitting etc.

Z

There was a slow motion video posted online somewhere (Youtube?) that showed the inside of a cylinder in a running engine. The valve could clearly be seen rotating as the engine ran.

Mike Simard

I know which video you mean. It's a misconception that the valves are rotating at the speed they appear to be in the video. I know you understand it Z but some otherwise smart people look at that and think the valves are rotating in real time which would be thousands of rpms. The video is shot with a frame every cycle over many cycles. There are also valvetrain videos somewhere that show the same thing. A little rotation per cycles looks like 10,000 rpm in the video!

Mike Simard

Adam, Jim Morton would know about this, hopefully he'll chime in. The 928 lifters seem to be made with a very wear resistant steel. It's actually been quite a concern because I'm machining camshaft blanks now and the material and heat treating are critical because of this serious lifter material. These lifters don't wear much, IMHO I wouldn't be too worried about reusing them or mixing and matching. The ones I've measured all have about a .0005" convex crown and the wear on used ones is a trace amount.

Erkka, I'd like to hear about substitutes, please let me know if you learn anything. The 4 valve 928s use a 35mm bucket. The same size is used in VWs and Alfa Romeos. The Alfas are interesting in that it might be a way to get a mechanical tappet. The VW INAs are certainly common and IIRC the measurements are the same, the only one I don't know about is the oil groove.

Imo000

Ohh no...... it's another DANGLERB!!!!!

Imo000

Why bother? If a used one with 200K miles has no measurable wear you know it's one tought MO FO surface.

Lizard928

I would have thought the answer was pretty obvious,,,,

they are of course made from unobtainium!

It is the hardest, and most difficult metal to produce, and of course is costly too.

Vilhuer

Do all reground cams have same angle? If not, what will happen to lifters etc? Thinking about long term effects of having cams lobes done.

atb

Can't speak to valves rotating, but I've seen tappets rotating while hand turning the motor while doing cam timing.

Kevn wrote:
I don't consider it a side action if its on topic, which it is.

I'm curious as to what people's theories/experiences are with this. Until I came to the 928 engine, I've never run mismatched cams and lifters. In highschool I had a friend that got a good deal on a used cam for his Mach 1. He installed it without changing out anything. A year later when he removed it, there weren't two lobes that had the same profile any longer. That experience sealed the deal for me: used cam-indexed or new lifters. I've swapped a couple of camsets on my 928 now, and never had a problem with wear. Just curious as to why. If the lifters are so hard, why haven't the cams lobes been ground down to tiny stubs? Is it due to the comparatively wimpy valve springs our 4 valve motors use?

Jim Morton

Adam:

I just caught this thread and saw that Mike mentioned some of my work with 928 cams that I am doing. As I am not really into typing (or public debate), I will keep this brief. Given what you have mentioned, I can suggest some checks to do as part of your development.

1.) If you want to risk using old lifters, at a minimum check the lifters for flatness ( if supposed to be flat) and any signs of lines / pitting / galling. IMHO, re-using lifters is a huge risk given the value of the engine...however people do seem to do it. If you insist on using old lifters, consider asking your cam person if they can re-surface them to the correct finish. FWIW, given the hydraulic lifter in the 928 and its use in some non-Porsche's, I would spend the $$$ and get new ones, although not likely from a Porsche source. If you search on the INA manufacturing of this lifter, you should have no problem finding this lifter as used in other engines. Going this route gets the cost of the lifter down to a reasonable cost, although not quite down to SBC. (No slight intended to any of our sponsors...) Regardless of what lifter you choose, make sure to use a good moly break in lube on the cam lobes / lifters, that is after doing item #2.

2.) As part of your engine test assembly, I would wipe test ANY cam I was thinking of running. A wipe test is done with "prussian blue" and lets you know where the cam lobes wipes across the lifter. In short, the wipe test is a good QA test of the cam and how it fits the lifter / head. I would never rely on indivudual component dimensional checks as a substitute for this test. FWIW, using a wipe test, I have caught major OEM manufuacturered heads / block lifter bore machining as being unacceptable for running any cam other than the stock unit. If you are going with an after market cam, this test is a must.

I could go on for a while on all of the aspects of choosing / fitting cams, but like I mentioned, I do not type very well. If you like, drop me an e-mail and maybe we can work out a time to chat on the phone...

Regards

atb

Thanks for chiming in Jim. I'll probably email you as I get closer to the install.

There is a local cam grinder here, Delta Camshaft, that's been around for awhile. I was going to bring in my DEVEK B1's and have the grinds plotted. Louie had suggested that I have the exhaust cam modified to help out with the fact that I'm running these with an A/T. Once I get to that point I'll send you an email.


On the wipe test you said you use "prussian blue", I'm not familiar with this. Is this the similar to machinests dye, that brush-on purple stuff? On the wipe test are you looking for a particular contact pattern, or just maximum contact across the width of the lobe face?

Thanks again everyone for your comments so far.
What I'm hearing then is that the lifter crowns are untypically hard and so they don't wear as easily as other manufacturer's. Since they aren't wearing, the lifters are close enough to spec regardless of being used that it's all the same to the camshaft.

I'm still going with new, but I do think its interesting that there have been so many cam swaps and the lifters haven't seemed to be an issue.

BC

The durability, as I mentioned, is an issue with NEW pieces. I would be very concerned. but nor am I suggesting only using old parts.

BC

So the concern in using used lifters is that they will accelerate wear if not within spec? On themselves or the "new/different" cams?