bcdavis

What about billet cams?

Camgrinder

I have ground billet cams for 944 4V . They require a lifter that is compatable with the steel. So far I have only seen non-hydraulic lifters like this.
Really nice stuff, but very high price.
The best part is the all steel timing gear, not like the factory gear that goes away when you lose the tensioner.

Fastest928

We purchased 40 ship sets of 2 valve camset blanks from the factory. We have a few left.

A few years back, we were prepared to buy another 40 shipsets of 4 valve cam blanks, I was going to order if we received 10 confirmed orders....no one ponied up...don't blame them, the cost was very high compared to welding. No need for 500 cams/sets/etc. Just 40 sets.

If someone has welded cams in a 928 that has over 40K street miles on them, I am all ears.

There are some folks who are making cnc billet cams...Sterling has a set...but time will tell on that case. If the hardness fo the cams is correct, and it is the right material, all should be good.

German chill cast iron is still the very best cam material in my book

Regards,
Marc
DEVEK
unwelded after all these years!

Fastest928

BTW, I have never heard of a 928 "losing" the tensioner..it is a issue with 944 tensioner mounts...they crack. Do not know why.

Marc
DEVEK

Camgrinder

To make the cam blanks reasonably priced a new core box for chill-casting would have to be made. (500 min order) Getting the real German ones is expensive.
We have 944 2V blanks and they are awesome. More lobe material than the German ones, so some really big lobes can be ground with a factory base circle.

I was only referring to 944 billets, I also have never heard of a 928 tensioner failure.


I never heard the definitive reason why idling is harder on camshafts..... but you are correct.

fst951

Hi Brad,

I have a couple of questions for you. Why would using a steel camshaft with the same level of finish grind and same surface hardness require a solid lifter rather than a hydraulic one?

Secondly, do you truly believe that if the 928 camshafts were made of steel that they would survive a 6500 rpm tensioner failure? That I find very hard to believe. I suspect you would still loose a couple of teeth.


Sure would be easier to replace the gear, however. I have sent a few sets to Jay at Part Werks and they replace them with a nice print industry steel quality gear. Never failed with all the sets I have had done. Do you guys at Elgin offer regearing?

Thanks

Camgrinder

The steel cams I ground were 8620. They were made for an SCCA car which used aftermarket lifters. Its not a question of hydraulic vs solid, rather the material issue. I would have to hardness test the factory lifters and compare the hardness to the finished cam lobes.

I have no idea about a 928 tensioner failure, but im sure the steel gears is 100% stronger than a factory gear.

We send them out to get re-geared.

fst951

I agree about hydraulic vs solid, it really dosen't matter for material choice of the camshaft. That is what I couldn't understand about your post. You made it sound like if you went with a steel camshaft you had to use a solid lifter. Go ahead and give me the lecture on why idling is so much more difficult on the lift lobes than at higher rpm, aside from lower oil pressure that is. This is good information for uneducated people such as myself.

Also, how much do you charge for a re-gear?

Thanks

SharkSkin

I thought the issue, which I have heard many times elsewhere and was alluded to by Marc, is that at idle there is more nose pressure on the cam than there is at high RPM. Apparently the inertia of whatever the cam is pushing(depends on the engine design & layout) tends to unload the nose and the backside of the lobe. Makes sense to me, but if I were an expert I'd be doing business in this arena myself, so take it for what it's worth.

Camgrinder

What Dave is explaining is "lofting". Where the lifter loses contact with the camshaft lobe at and after full lift. This tends to reduce the over the nose pressure at high RPMs. If you have too little pressure you end up pitting the flank just past the nose of the cam on the closing side.
At idle the spring is not subject to as much force (lofting) , it is not resonating at a high frequency (might reduce pressure) , and has all its pressure to exert on the cam lobe. Combine that with a reduced nose radius of a racing profile and the lbs/sq in goes way up. If you were to idle a "full race" cam with excessive spring pressures as if it were a street car, it would not last very long.

fst951, I didnt intend the post to mean only steel cams need solid lifter, I meant the only ones I had ground were mated to aftermarket lifters. The hardness of the two components were compatible.
Sterlings cams are steel, and he is using stock Porsche lifters. I didnt make those cams so I dont have all the details such as rockwell hardness etc. I am hoping he has good results.

Fastest928

Repeat:

"BTW, racing is EASIER on cams then a street car idling! Nose pressures...."

Again, 40 sets for 4 valve casting from the factory.

We hase a few factory raw castings left that work with factory lifters.

Marc
DEVEK
Done with this thread....