Jim Morton

Ryan (et al):

Mark might be stating things a little crudely here with "lopping off"... but yes, to make S3 cams usable in an S4 head the cams need to be shortened (or plug the 5th oiling hole, pass side EX cam) as well as one cam (drivers EX) bearing surface / thrust face needs to be modified with the thrust face moved back to fit the wider journal of the S4 head.

As reference to the cams / valve events, the lobe profile (lift / duration) for the S3 and GT cams are the same. However, the S3 intake has an 8 degree later lobe center angle of 121 degrees vs. 113 for the GT.

With regards to having S3 cams made usable in S4's, this is a straight forward job if a shop is willing to setup things up vs. what a customer might pay. On a one-sie / two-sie basis, I doubt the job would be worth someone's time vs. what folks might pay as there is lots of setup simply for modifying the bearing on one EX cam. IMHO, folks should consider the point of view of "worth it or not" to a shop when many of the psuedo DIY mods get mentioned.... $0.02.

As another reference point related to Elgin Cams. Back when we did Dennis' engine, Dema Elgin had a machinist associate willing to do this S3 cam mod work. Neither Dema or his direct employees actually did the work in house. After the last batch of S3 cams done at Elgins, the machinist has since bowed out of being interested in doing this work anymore. With this news from Dema, I am working to tool up my lathe and solicit help from a welder friend to modify some S3 cores I already have as I would like to regrind my cores with the same profile(s) as used for Dennis' engine.

FWIW, the issue of "lopping" off the cam is not a big of a deal as long as the cams are regorund befoire being "lopped" off. With regards to the bearing mod, the only real issue is holding the relatively long shaft on centers while supporting the cut at good accuracy to produce a seat for holding the new thrust ring. Accuracy at placing the new thrust ring on the cam core pays big dividends later when fitting the new ring within bearing toloerances.

For completing my own tooling setup, I needed a steady rest for my Monarch 10EE lathe. Given that my lathe is not something common to the Harbor Frieght catalog, finding / buying a steady rest for the Monarch is somewhat like finding good, used 928 parts... Anyhow, a steady rest is now enroute to me and with it, I will finish modifying several sets of S3 cam cores with Dema's shop as their next stop.

In short, given what was learned with Dennis' engine, I think the S3 cams make for great re-grind cores. As far as running them at stock profile... IMHO, the profile is not all that "hot rod" to warrant the use of used cams with adding on the cost / hassle of getting the cam modified for fitment.

As one more FYI... For someone with a GT needing a single repalcement to a "GT" EX cam, modifying the S3 EX cam(s) makes for a larger pool of good cores. In this case, the cost / hassle of the mod work might be worth it.

Regards

mark kibort

Mine were done much differently than how Dennis'. because dema and others said you cant really weld on the cam, Todd suggested fabricating a sleeve and knotching the cam (cut it square) and welding it together on the cam.

I guess after all that is done, the cam ends can be lapped off

In retrospect, i would have taken a .5mm off the base circle now that we know that the lifters can handle the extra pump up.

mk

Glenn M

Thank you all for the information on the S3 cam conversion.

I'm getting the feeling this isn't a very cost effective undertaking and difficult to find the proper folks for the job.

If the cams aren't cut sounds like the head needs a drainback hole opened. Can this be done safely without the head removed?

This is all great info for me and other thinking about doing this modification.

Thank you,
Glenn

Jadz928

After all this interesting talk, it seems Carl's cams are a pretty good deal. 2K for the cams made-to-order and more aggressive than the S3's. 1K to install.

$3K installed, and no development time in it for me. All the leg-work to get some S3 cams or whatnot made-to-order... that time adds up. And in the end, you hope all goes well with who you used to do your machining...etc.

IcemanG17

its a serious bummer that Elgin is out of the cam regrinding business.....thats a big loss for us 928ers......

Bill Ball

As Jim mentioned above and Errka noted in the earlier thread you linked in your first post in this thread, it is an exposed oil feed that needs to be plugged if you don't cut the right side EX cam. All the oil in the head drains through 3 large openings down into the crankcase along the outer wall. There is no oil drain that needs to be opened. That said, plugging the oil feed is best done with the head off if you intend to tap the feed hole to accept threaded screw plug, although tapping CAN be done in-situ if you are comfortable that you can trap the debris using a greased tap.

Bill Ball

Brian: Re-read Jim's post. Elgin still grinds cams. He just doesn't want to do the thrust bearing mod, which he was sub'ing out anyway.

mark kibort

How is there an oil feed exposed if you DONT cut the cam ends off?

I would have just taken a hack saw to mine if i didnt have elgin put that sleeve bearing on it.

mk

Jim Morton

Mark:

As Errka and other have noted, there is an additional oiling hole on the S4 head for th wider EX bearing journal that is not on the S3 head. The S3 cam bearing for this locale is shorter and will expose this oil feed hole if not plugged.

I missed this little tidbit when assembling Dennis' engine. You saw the results up at TH... massive amounts of oil pumped into the passenger side head galley. What a mess, as well as a stupid mistake !

IcemanG17

Bill
OKay I get it.........duh...

mark kibort

I guess I still dont understand. Didnt dennis replicate the S4 bearing surface, so that the S3 cams were the same as the S4 cams and that wouldnt matter.

I didnt do anything with the oiling holes. Actaully, the holbert cams had some nice little oiling grooves with elgin kind of replicated.

I didnt plug any oiling holes and dont have any issues.

Ill have to check out dennis' cam mods. maybe elgin didnt replicate the bearing all the way as mine was made.

edit: Here are the pics of dennis' mod to his cam, the bearing surface and oiling holes and last min in the bearings with the slightly different collar added with my heads with cams installed to show the lapped off ends.

dennis' are no different than what I installed and they seem to replicate the S4 DR exhaust cam in the bearing and collar area. so, where is the problem?

mk

mark kibort

Im confused. Jim seemed to be talking about the bearing surface near the cam pulley side, an I thought we were talking about cutting the ends off the cams that are not needed in the S4 head installation. are their oil drain lines that would be plugged if the S3 cams were used with S4 heads? otherwise, why would there be an issue besides having an extra , uneeded bearing area at the firewall side of the cam that doesnt need to be touched on an S4 cam job. (because the cams dont have the ends like the S3 cams)

mk

Jim Morton

No. I was talking about the bearing journal in the head for when the cam is left long.

When the pass. side EX side cam is left long, the S3 long extension of the cam rides on the bearing surface used for the driver's side EX cam thrust. This bearing journal in the head has the fifth hole needing to be plugged for use with S3 cams.

FWIW, Errka's post from March 2008 discussing his engine project has a great photo of the issue.

mark kibort

so, are you saying that he didnt lap off the ends of the cams for the passenger side thrust bearing surface? If it is being used by the cam end, and wasnt before, I still understand how that would effect anything. what am I missing.
Dennis has S4 heads, there is a 3" gap to the area you are talking about, if he lapped off the ends, what would need to change? if he didnt, how does the presence of a cam bearing now, create some kind of oil flow in that area, unless there is a plug in there normally that is removed to provide forced oiling to that cam journal. (now Im guessing)

edit: I cant find that picture from Errika. can you give me a hint here?

mk

Jim Morton

Your guess is correct.

Normally on the S4 heads / cams, these holes would have plugs in them. The idea was to keep the cams long to: 1.) not have the rear most lobe cantelevered and 2.) we thought there is no real harm in having the extra length.

The issue is the one, darn oil hole that does not get covered by a ground bearing diameter journal for the pass side EX. The rear journal of the S3 cam is not long enough to come forward enough to cover the oiling hole.

Sorry for no pictures, but once you are looking at this with actual parts on the bench, it's pretty obvious to see the problem with the rear most dual cam cap removed while resting the pass side S3 EX cam in its bearing saddles.

For Dennis' build, it is VERY unfortunate to have been so focused on the drivers side thrust mod to have missed plugging this small, but important oiling hole. :^(

Having now gone through this mistake... simplest soln is to shorten the cams to match S4's and follow the WSM for which oiling holes get plugged in the heads. Not putting a plug in the one darn oiling hole is a mistake not to be made again.