Shaun @ Tru6

Got some work done on the motor tonight. A week ago my friend Chris grabbed the flywheel and shook it and sure enough, the crank went kerchunk so for the last few days I've had dreams of a cracked block from thrust bearing failure. Given the relative minimal machining of the bearing down to copper, I think I'll be OK. I'll pull the crank out tomorrow or over the weekend and get it to a machine shop next week.

Looks like someone was welding inside the motor.

Shark_gts

I'm not an engine builder but isn't the block/crank toast? If the flexplate sees (axial) load how will the crank counterweights stay off the block now that the bearing is that far worn?

I found a shot of the heads we pulled off the '89 car. They were nice. I believe you can see where the gasket breach was, at least where I suspected it to be. We sent the heads to a German auto machine shop to get inspected (I think they tested them too), & cleaned just in case there was a warping issue. They checked out fine in all areas.

Shaun @ Tru6

and it's done. Now it's pretty much experts/machine shops checking tolerances and confirming everything is OK. I may have Bob at Anchor Atlantic do the heads. I still need cams and should probably get new/better cam gears. Given that I need cams, is there a go-fast grind I should look at? Now is certainly the time.

Shaun @ Tru6

Heads look nice!

I am not sure what you are saying here. As I said when I posted originally, I'm a 911 guy, not an expert on 928s, but from the little bit of research I've done, I should be OK with new bearings. If the thrust bearing had spun or worn way down, then the case is toast, but I think I caught mine in time.

We'll see.

jcorenman

Shaun,

Great thread, sorry to have missed it until now!

Cranks are just about indestructible, block should be fine-- thrust bearing is only down to copper, not beyond. Have a careful look for cracks around the thrust-bearing web, Alusil is hard but brittle compared to most alloys.

Did you find cams? S4 cams are the most-available and lowest-cost option, and a good match for an auto. The sort of damage that you found is unusual, my guess is wrong oil (maybe 10w-30 with low ZDDP?). Remember that 928 Int'l is having their annual half-price sale, great folks.

There are other cam choices, but none that are cheap/good/reliable-- one of those old "pick any two" games. My suggestion would be a good set of used S4 cams and new lifters.

Cheers, Jim

Shaun @ Tru6

Thanks Jim!

I've been working with Mark at 928 Intl, great guy, and he said he's got 4 nice 88-91 cams for me, $125 each which seems like a good price after the 50% off deal. I'm sending the heads down to Bob at Anchor Atlantic to be reconditioned.

Mark said he's seen this wear on GT cams but that it is unusual for an S4.

Good advice on checking for cracks, I have some time set aside this weekend to carefully go over the case. It's a true engineering work of art. Makes a 911 case seem quaint.

Tell me more about needing new lifters.

jcorenman

Correct. The GT cams have more lift but the same springs, and tend to get pitted just past the lobe-centers from being "tossed" at high RPM.

I am not sure new lifters are needed, that was just a suggestion-- and what I would probably do out of an abundance of caution. The guy whose opinion I would trust the most is Greg Brown, but you just called his fuel line "ugly"... [Full disclosure: Greg is currently building a motor for us).

In general cams and lifters, once they have worn together, ought to stay together-- that's just good practice in general. On the other hand, from what I've read (mostly here) the original 928 lifters were quite hard and don't wear much. So new cams, used original lifters, probably OK but depends on who you ask. Used cams, different used lifters, not so sure.

The catch is, again from what has been posted here, is that the new "lightweight" VW/INA lifters don't have the hardness of the original lifters. Does that mean that used but good original lifters are as good as new not-so-hard lifters? Dunno. The real question is whether your lifters will live a long happy life with a different set of cams, and I don't have that answer to that.

In very round numbers a set of lifters is twice the price of the cams, right? In that case I could easily be talked into reusing the lifters (as long as they are pretty and not scored) and then checking up on them in 20-30K miles.

Shaun @ Tru6

OK, good to know, thanks.

I have to look at the lifters again but if memory serves, they were pretty nice. But given the cams, now I have my doubts.

I may wish I stuck to rebuilding 911 engines after all of this but I was surprised at how easily this motor came apart. I'm a fan! But this engine is an onion if there ever was one.

Shaun @ Tru6

Busy weekend so I didn't get a chance to do as much as I wanted Jim. Just looked at the lifters again quickly and I think about half are no good and will toss those. I got a piece of ground stock for any that don't have obvious pitting to determine which of the remaining are keepers. Flashlight tells the story. Once I have a complete set + 2-3 extra, I'll send them to Craig Garrett (cgarr over on Pelican) to be surfaced. They won't be new but certainly won't cause any problems with new/used cams and are probably better than the INA ones. Building crates for the heads tomorrow to send those to Bob at Anchor Atlantic to go through.

Slowly but surely.

2 good, 4 bad here, 1 keeper at the end.

The Deputy

Shaun,

Looks like you are leaving no stone unturned. I've enjoyed following along.

Brian.

928phantom

There is a guy on facebook selling GT cams for 800, milage is alittle high but maybe you can use that as leverage to get his price down, probably the best stock cams you can get....

https://www.facebook.com/groups/5649...6703303091570/

Shaun @ Tru6

Thanks, good to know. What are benefits of GT cams without a GT DME and other pieces peculiar a GT vs. and S4?

928phantom

here goes the spec list on the cams, the GT cams have more lift and such, should add a few HP, like 5~10 maybe...besides that I think the GT/GTS intake manifold is alittle different, I've read about people picking up a few ponies from that also, but not much...

http://members.rennlist.com/pirtle/zeng_cam_spec.txt

jcorenman

Shaun,

GT cams are arguably the best factory cams for these motors ("arguably" only because everything gets argued here...). That's a killer price BUT only if they are in good condition, welding cores otherwise. And more of an advantage for a 5-speed, mid-range torque is about the same but they have another 10-20 at the top end.

PM also sent.

Shaun @ Tru6

Lifter art. Not quite Serra, but if I can put an exhibition together, I could possible fund a stroker build.