For what it is worth, the pistons in my early 87 have big 2's on the top of the pistons.

 

Huh??? 86 cams are basically GT cams, but actually a little better on the potential HP department. mod to make them work in an S4 head is about $400, not $3000!

just change the cam and you have a GT engine for all practical purposes, unless you plan on selling it on the rare car sales TV show.

 

I'll second Mark here. Something's not right. He spent $3k to get the driver's side exhaust cam modded to fit S4 heads? Or to somehow have the chain gear modified on the S3 intake cams to advance them 8° to match the GT spec? That doesn't make sense - the price, the work or the goal.

S3 cams are still available and relatively inexpensive. When I bought my used set from 928 Intl, they were in stock.

 

I think the casting revision .3R heads were installed on many GT's, maybe that's the difference between .2R and .3R? I have never seen a .3R head, wo that would be interesting.

Is there a web page (or even just a thread) that has photos of all of the different cylinder head casting revisions? Even better, with annotation that would explain the differences? It would be worth the bits and bytes.

 

Any recommendations for good machine shops preferably on the east coast (closer to Boston the better) for modifying S3 cams to fit S4 heads and possibly decreasing base circle while at it?

If I recall from previous threads the guy doing the mods for Elgin was no longer with them, right?

Would be for early vin '87 (most likely a squirter block etc)

 

You should PM Jim Morton on this topic.

 

roger that.

 

My cam was done on the west coast. Last I checked, Jim wasn't in this business anymore, but I've been wrong before. At least I couldn't get it done there. The shop I used did nice work, although I don't have the cam installed yet is was, way, way under $3000. I had no lobe work done.

 

I think he was changing all 4 cams, and grind them to somthing better than the GT cams for street use. Im not sure, but I do remember him saying about 3000 $ for all 4.
I just looked at 928 international and looks like their selling each cam for $495, so thats about $2000 for all 4 and another $1000 for grinding all 4 ???
I dont know how the prices work for cam modification,but for our Honda CBR 600, it cost us 670$ to change the duration to somthing smaller than stock on exhaust and intake.

 

Hey Guys... a couple of comments / corrections.

1.) I am not the Dema Elgin machinist resource that is not in the business anymore. Right now, I am working to become a resource to Dema so that he can feasibly offer some of his cam grinds to 928 folks.

2.) As of this post, I am in process with the S3 to S4 mod on (5) sets of S3 cams. As mentioned above, I am doing this work to create cores for regrind.

3.) In order to make the work task practical, it's best to mod the S3 cams in batches to make the most of the machine / tooling set ups needed. If asked to do only one cam, the cost would be higher as you would be doing all the setup work to do the operations on only one part. In short, the time needed for the effort is in the setups...

4.) S3 cores come up for sale pretty often. If you do a search here, I think you'll see what prices they trade at.

5.) Beware of worn lobes and consider the risk when offering to buy used cams, of any flavor ! Price accordingly based on what is known about the history of the engine and its past life.

6.) If anyone wants more details on possible cam work, please PM or e-mail me. Please know that I am not trying to withhold any info here, but I could post pages of details with most of the info being only relevant to who's ever project is at hand.

My e-mail is: jmorton@morton-engr.com

 

Firstly thanks for all the feedback.!
This is an interesting topic with many similarly interesting permutations...
I was hoping that I could just regrind and weld the original cams and put them back with the GT ECU.
I know a reputed cam specialist in Norway that probably could modify those S4 cams into something more exciting, but maybe I shouldn't take the risk...
Now I am starting think that its better to sell the whole S4 engine and look for a GT engine.
As described by Namaste GT..!!)))
Just missed one in GB for 2000 Sterling that was completely overhauled....!
Bummer!
But should I completely can the idea of modding the S4 cams..?
What if the chap in Norway gives me a nod that it will be fine and the price is decent..?
Will that be really idiotic to accept..?

 

I'm all for getting more vendors involved in modding stuff for the 928. But, when you talk to a cam grinder they don't want to get involved in welding up and then grinding a cast cam. It's a big deal that cam guys don't mess with. Make sure you tell him it's not just a grind, but a reweld and grind and I'm sure his price will change a lot.

 

Dont make it more complicated than it needs to be. all you need is ONE exhaust S3 cam to be modified. (I had the bearing surface pressed and welded to the cam, while Dennis had it spot welded in 4-5 spots to hold thenew bearing surface in place) . the other 3 cams need nothing more than the ends cut off with a hack saw (you know what i mean).

Then, you have BETTER than GT cams in your GT engine. one cam mod and follow Jim as to how that can be done. Then, if you want to go crazy, take a millimeter off the base circle for some big HP gains. If not, you end up with a full GT motor, without having to pull, sell and reinstall an entire engine!! Now that would be crazy!

as a note, Dema didnt even want to weld my cam at first. Based on Todds advice, we talked about just pressing two bearing surfaces together and welding them together without welding the cam. they then, just machined the surface to match the old S4/GT bearing surface configuration. Dennis had the bearing surface welded to the cam. in both cases, the cam needs to be then straightened.
when you are done, you have the driver side exhaust cam that matches the GT cam. all the other cams are the same. Lap off the ends and they are done.

mk

 

I sorta took your advice btw Mark....!
I sold the car and got a complete 1990 GT with a Strosek Ultra body kit.
Very happy to have the real Macoy!
Thank you for your feedback.
Now I am contemplating grinding my GT cams however..
I have heard that makes for some nice extra top end hp.
Cheers. Michael

 

No need to grind your GT cams... pull em and sell them.. and contact Colin (Lizard931 on here)..he's made some really nice (more aggressive) cams for a really good price...