912 Endplay- Need Real Answer

[914Ghost]

Can someone give me a definitive real world answer as to why to use ONLY the thick 912 endplay shim instead of 2 or more thinner shims to get correct endplay?
Seriously- I want a REASON, not just "thats how they did it".
I have now 6 different opinions from different VERY reputable and VERY successful Porsche engine builders- One being the late great Maestro hisself.
Also, can someone tell me why I can't (instead of searching the world for a ~ .0023" shim that will be wrong when I get it) cut the crank mating surface on the back of the flywheel (part with 8 dowel holes) by .005" to get it correct?
Don't tell me that the .005" is the difference that will cause the flywheel to fail. The dowels will protrude through the flywheel that much further for even better attchment from an engineering view.

Thanks!
Bob O

[cgarr]

Whats your endplay with the soft iron gasket installed under the flywheel and no thrust washer? I got my thrust washer from the local porsche dealer, I think they range from .80mm to 1.15mm .0315 to .0413 Is the endplay greater than .041?

Craig

[Sweetheart912]

Ghost,

From the 912 Engine Guide Manual (factory) I quote - "End play should be 0.14-0.17mm(.0055-.0067"), wear limit 0.22mm(.0087"). End play should be adjusted before installing the crankshaft. The use of one or more soft iron gaskets is not permissible. Soft iron gasket thickness is 0.10-0.14mm(.004-.006") /......./ install spacer of calculated thickness. The spacers are available in thicknesses from 0.8 to 1.05mm(.0315-.0413")."

Here is where I think folks get balled up-the factory is real clear about the soft iron gasket. One only - period. It does not say you cant run more than one steel end play spacer, even though it implies the use of one. I have often used two to get the exact thickness needed and had NO problems-even on race engines. VW 36 hp steel spacers are SAME specs & diameter and come in much thinner sizes so you can match it up with one of the Porsche thicker ones to get exact dimension you need for end play. I always try to use one but when using two, I always put the the thicker one on the flywheel/gland nut side and the thinner one on the bearing side.

Honestly, in all my years I never heard of anyone shaving off inner metal-but that doesnt mean it cant be done....BUT then I have cut flywheels down to 8 lbs and run them on race engines on a C crank when everyone else said pooh-pooh. If your machinist can cut that area, I would suggest getting the same amount taken off the dowel ends that protrude thru, so that you stay more aligned with the factory setup when you torque. As thick as the metal is on a flywheel dowel circle five thou shouldnt hurt anything. I would do it if there is no other way.

I'll tell you what a lot of us would do, was to do the math to get the magic number, then get the way thick Super90 end play shim and take it to the machine shop and have it cut to size needed. Thick Super90's were hard to find 15 years ago, so I don't know if any are still around...I'm all out or I'd send you one.

The important thing is your end play, which is the gap between the bearing flange & the flywheel shoulder, is RIGHT. I have always tried to get dead nuts on 0.0060" as the magic number, but you do have a range to play.

I don't know if this is definitive enough as requested, but it is real world from actual experience. Hope this helps.
Cheers.

[914Ghost]

wow.... .014" ? Really? ALL THE WAY TO .022" !!??
Damn, I don't know if I can leave it that loose. Thats a "clunk" when you pull on the crank. Even VW goes to .009" I think.
WITH the soft iron gasket and no shim I think I have .060" ...I'd have to measure again to be sure. With the think shim in I get .011".
And I get slightly different numbers with a couple different intruments I have used.
I've installed "too many" shims and snugged the flywheel up to get zero endplay and measured zero movement of the thrust bearing.
Thats the only test I can think of to check the bearing.
My thick shim seems to be .050" .
I have about 8 of the VW shims (36hp) all seem to be roughly .020" ... so and maybe one that's .030" . No combination of stacking gets me closer than the .009' to .011" area.
I figured .005" was the magic number, cut right off the back of the flywheel - and it would never be noticable.

To double check my numbers, I actually put the thick shim in and slid a feeler guage .005" through the #3 spigot inside the engine bewteen crank and bearing and measured it- I got .005" .

Those factory spec's scare me. I think I remember hearing those numbers before and still set my S90 engine at .005" .
To me that's just barely perceptable movement when you yank on it- and thats enough.

i'll keep working on it.
Bob O

[Sweetheart912]

Bob, the numbers in the original post were in MM not INCHES. Should have clarified so not to mix anybody up. I just edited the original post to spell out MM after each number set & added the INCH equivalents. Sometimes I just assume things, or have senior moments :-)
Take care. Oh, I'm curious, what did you decide on the P/C set?

[914Ghost]

Oh...*****...good.
Thats scared me. Maybe I didn't read close enough.
Just so used to inches because that's what all the machine shops and guages read in.. ..

On the P/C's I found a set of Factory Mahle's, a guy I know has 2 sets, so I can choose the best 4 for $200. The other set will be for sale, might be more or he may want to Ebay them, what are they worth?
I just don't trust slip in big bore kits to begin with- I know they're probably safe, but as stout as these things are designed, heat is still the killer- epecially at the Heads and Barrels.
And USED big Bore P/C's. ..? Maybe on a Bug engine....you can build those for 50 bucks. Not on this thing.
Anybody against re-using Mahles?
-Bob O

[cgarr]

.060 is a lot! mite be time to crack the case and check it out. I know if your using all the original parts, with new bearings it should come out real close to spec. I have seen some where its the bearing thats working back and forth and not just crank endplay.

cg

[914Ghost]

Well-
After searching and talking and thinking and thinking...I had .005" trimmed from the flywheel.
Back together with ONE, count'em- ...ONE thick endplay shim.
My gauge is from the ...well it's old - but it reads .003" to about .0045" with all together - shims, metal gasket, and flywheel seal.
Done and done.
Don't yell, it works!
And no worries- dammit, I'm having the tin powdercoated 90% gloss black. it's give and take with you guys.
-Bob O
OH! Also, got a GREAT set of factory Mahle's with rings - $290.
No more NPR.

[914Ghost]

P.S.
I need a crankshaft pulley.
Anyone Gots one?

[porschedreamer]

914ghost: i cant wait for the "build diary" - you gotta put up a page!