outbackgeorgia

Wow! What a pair of threads.
Carl has laser matched the gear profile, made some enhancements and the only data anyone has are some photos to say he has made a "completely different part".
If it meets the "drawing/specifications" has correct material, hardness, etc. I am willing to bet my 32V engine on the new parts. I don't wait for millions of hours for a new radiator to be "tested", or a new bolt or washer or shock or valve spring, etc. Most of you don't either.
Replacements parts are made separately from any production line and are made to specifications that assure a quality part if made correctly. Usually, replacement parts are not "overruns" from production (production ended in 1994/5 anyway), so all replacement parts we use are made to "drawing/specifications" and if those are right, what is the issue?
Dave

T_MaX

Yawn, you guys are sucking all the fun right out of this forum!

Lizard928

Dave Davis,

if you look at the picture of the two gears posted, it is clear that the profile of the gear is different.
It is as of yet to be determined if the profile is enough to make a difference.
This is why I have asked Carl for a few high resolution pictures of one of his gears wrapped with a gates belt (contis are crap). This will help me better determine if I feel that the gear is a suitable replacement, or if it should be scrapped and used as a learning experiment.

One of my biggest fears is that if one were to purchase them, and then install them on a motor, and the teeth did fall off the belt causing failure. It is likely that it would happen after say 10-20k miles (service interval of 60k factory), that it would be past the 1 year mark and no one but the owner would be "burnt". As well, it would be VERY difficult to prove 100% in court that it was the gear profile that caused the belt to fail.

Carl claims that he had a 04 gear laser copied, and if he did then the tooth profile should be identical to the factory gear. But the pictures do not show this. And it has been shown that the 04 is identical tooth profile to the 00-01 gear. So it needs to be determined if they are the same, and if they are, then I see no problem with Carl's gear, but if the profile is not EXACTLY the same, and I mean down to the last .00001" then it is unlikely I would EVER run it in any car that I serviced. One reason that if something fails and I have to work on it, I may get burnt and that wont happen.

Dictys

If the photo's are not taken from exactly the same location, distance etc then there will be visible differences in the image even if they are identical, let alone taking into account barrel roll etc etc you get with a small digital camera.

I would trace each of the tooth's profiles on paper then lay them on top of each other, I suspect in real life (not photo's) they are the same. Just my 2p worth.

the flyin' scotsman

Life expectancy for me and the 928 is too short.

Carl has offered an alternate, its priced similar to the Porsche product, its unproven in the field.

We have choice so grow a pair and choose.

Roger, my previous inquiry still stands. Im in for a full set of cam, oil pump and crank gears from Porsche pls. (prior to these threads)

thx

Carl Fausett

That's the point is was going to make next, and you beat me to it.

I remember when the improved 04 version first came out how many screams there were as to price. Now you know why. The early version was cast, made from a lower-grade alloy suitable for casting, and PTFE coated on the wear surface.

If they went from a cast part to a machined part, and they upgraded the material to 7075, then you have the explanation for the increase in price.

It also supports my claim about deflection in the belt crown. Porsche does not spend money they dont need to spend. If the early sprocket was good enough they would have just cast more. By going to 7075 they added structural strength to the crown of the sprocket to fight the deflection that I have reported. I did it a different way, by using 6061 (easier to machine than 7075) but added section to the crown radius. Both Porsche and I were addresing the same problem, IMHO.

They did it with an alloy, I did it structurally by adding more material to that area. Then I lightened the non-critical areas of the webbing to make my new sprocket virtually the same weight as the factory one. A heavier sprocket would add belt load, and I did not want to do that.

heinrich

It seems a bit of a far fetch that, with no further development after 1994 on any 928 by Porsche, and after exactly zero reported failures anyone is aware of, of flex in the cam gears causing problems, that out of the blue Porsche's development team in 2010 upped and decided to supersede the gears they had sold and installed on every 928 since 1985, with something they had developed and considered a better option.

The more likely scenario is that the original manufacturer simply does not exist, or does not manufacture the gears anymore, and Porsche sourced an alternative supplier who - for better or worse - follow Porsche's exact design specs except that now (unverified) the new gears are a better quality.

RKD in OKC

A LOT has changed in both manufacturing process and materials availability since our cars were made.

10 years ago I ordered some special progressive front springs from Porsche Motorsports USA for my 89 944 Turbo. I had to go to Porsche Motorsports because all the other suppliers said the were NLA. Porsche Motorsports showed 4 in stock at the factory for $200/pair. Two and a half months later I finally got the springs. I was told inventory was wrong and that Porsche had to do a manufacturing run on the springs to fill my order. Was told that since I had a standing order they would sell the to me for the original $200, but the price had increased to $600. And that was 10 years ago.

Four years ago I got another 944 Turbo and wanted the same progressive front coils. Not only were they NLA, BUT I could not find ANY spring manufacture that could even make the spring. It was progressive not by coil windings, but the wire was tapered. No one could make a spring from tapered wire any more.

ROG100

The main reason Porsche changed the cam gear material was because of the large number of warranty returns on the 01 gears.
We all have been aware of the softness of the 01 material with a very poor spray on wear coating. We have all seen the accelerated wear of the gears once the wear coating disappeared.
The original manufacturer of the 01 MWU is still in existence and I talked with them a couple of times back in November last year. I am sure Porsche has a number of suppliers who could have supplied this 04 gear and shopped around for the best deal. KWG was that company.

928er

where is the info that the new material is 7075? if that is the case, then sign me up for a pair.

BC

Unfortunately, as you can see from my pictures, I have the 01 gears that I bought new. I will not be spending 700 on gears when I have new ones on the engine on the stand. But since all this was going on, and GB thinks I made my head studs too tight, I will take it apart a bit and get these hard anodized somehow. That probably will make them actually cost what a new set costs, but thats the way the cookie crumbles (or wears prematurely)

928mac

I would just run them for as long as they last 2-3 years and watch for a sale on new ones. but thats me.

Imo000

I tought the original thread said the new cam gears were lighter than OE. Or am I wrong?

namasgt

I would think if the gear was deflecting like the way your describing Carl, we would have engines failing left and right from a broken cam gear. Crack propogation and then failure. But that is not the case, is it?

Carl Fausett

Not what I said. I said uneven loading on the cam gear causes uneven wear of the anti-friction coating, and therefor shortens the life of the part.

If the load were distributed more evenly across the entire surface of the crown, the anti-friction coating - and the part - would last longer.