S-4 cam re-grind
 

A quick question for the cam experts. Can S-4 cams from a 87 S-4 be re-ground to gave the same profile as the GT cams and then be used in a 1990 GT.


Thanks
Dan 1990 928GT

There are only two ways I know to get S4 cams to GT spec. and beyond. Most modify the cams beyond the GT specs. Devek's B1 cams are an example.

One is to have them welded. This is both expensive and not recommended for street use.

The other way is to have the base circle cut down and use lash caps. There are several motors running using this method, but it's not ideal.

Are your current GT cams bad?

Thanks John.

My cams are ok but I saw a great deal on some used S4 cams and I was wondering if they could be modified for use on a 928GT. I would have them modified and keep them as spares.

Dan 1990 928GT

Something like this? Yes these are for an S4 - the one in my sig:

https://members.rennlist.com/hacker_.../cam%20A7s.jpg

More pics are on the way.

Thanks Hacker, who did the work and what sort of cost are we looking at?

Dan 1990 928GT

Okay, Spill it Erik.

yeah, any more info on this topic?? so how do devek do there cams, are they welded?? im sure i remember marc saying he had problems with some welded cams a while ago...

i had my GTS cams reprofiled with a smaller base circle and it took them very close to GT spec and i was still able to use the existing lifters without lash caps.

Sorry guys, I've been swamped with customer projects. I hope to have the rest of the photos of those cams uploaded tonight. I don't have the details yet as to where they came from - I need to talk to Todd about that.

Phil at 928 developements still does cams. I have no experience with his products, but they are an option:

http://www.928developments.com/stree...t_packages.htm

According to Don Hanson's past-experience with Phil Threshie and his cams, there's no way I would do it.

What experience is that?
Hammer

Cams
 

They were done at Elgin Cams, same place and same welded up method
as Mark Anderson has in his mtr, They are GT cams to start with, then welded
then hard surfaced. This method done by Dema Elgin himself has proven to
be reliable enough for Mark's race motor for the last ten years -- thats good
enough for me. The specs are
int - dur exh - dur
274 270
int - lift exh - lift
.412 .388
The base circle was not altered
944 S2 springs
ported heads & big valves

The ’85-86 32V cams are very close to GT profile but they need extensive machining to fit into the S4 head.

I wouldn't say extensive - Todd came up with an adaptor / sleve to get the job done. IIRC he's running this setup in his car.

I forgot to take pictures of this design the last time I was there. Hopefully I'll be there again this weekend dropping off my new SC pulley for modifications. I'll take some pics of the modified cams.

not extensive. a sleeve that is welded together, around, not to, the 85cam and they (85cams) are close to identical to the GT cams (or the cams on the holbert car)

here is the before and after pics.

MK