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Crank End Play, Should I be worried??
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Max Welton
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PostPosted: Tue Aug 29, 2017 8:40 pm    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

EVfun wrote:
The given clearance numbers are for oiling the bearing thrust faces and assume no bearing movement in the block, as far as I can tell.

The endplay spec also allows for the oil films between each pair of shims.

... so make sure each shim is FLAT.

Max
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QuentinRN
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PostPosted: Thu Feb 10, 2022 9:09 pm    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

1 - No it doesnt...the thrust face of the bearing itself wears without the bearing being loose in the case.

2 - But not every failed #1 main bearing needs the case thrust cut,only when the main 'walks' in the case.Its important when buying bearings for a used linebored case that you check the thrust cut measurement,its difficult to spot by eye.

3 - With excessive end play, the case eventually gets shredded. It is very easy to fix (just remove thin shims and replace with thicker ones). Remove the engine in a couple of hours, and 15 minutes to get the shims correct. Then you can have peace of mind knowing it is correct. Much cheaper in the long run.

ALL OF THE ABOVE COMMENTS ARE INCORRECT.
1 - The front thrust surface of the case gets worn (and the front main bearing flange wears) BECAUSE the bearing gets loose in the case and slides fore and aft. 90+% of the case wear is on the front side because stepping on the clutch pushes the flywheel and crank BACK toward rear of engine. The main bearing is clamped tightly in the case by the crush of its full diameter AND the crush of the two flanges that are designed to keep it from moving fore and aft.
Sometimes the diameter of the #1 bearing (and the other three, mostly #2) get quite worn/loose WITHOUT the #1 flanged bearing wearing the case saddle. But the #1 main bearing is NEVER tight in its diameter if the thrust is significantly worn. The thrust face of case CAN'T "wear" unless the diameter of #1 bearing bore hole is loose. Anything in that area can be damaged and even sieze from extreme heat, lack of oil or even too little end play to start with. When #1 siezes in those circumstances, the tearing of metal and "laid over" 5mm dowel pin are typical signs.
2 - Yes, these things are somewhat "difficult to spot by eye". Even when you have examined & rebuilt 2,000+ VW engines. Thats why each part needs to be examined CAREFULLY with precision measuring instruments. They are not that expensive compared to doing an engine several times. Most of the specs are not hard to find in the BENTLEY manuals. The CRUSH figures are not so easy to find. But one to one and a half thousandths (.00016 mm) crush lateral and axial are about right for #1 main bearing.
3 - No. Not easy to fix in a few hours if the #1 bearing is loose in the case. Re-shimming could even make it worse, as others have observed here.

These problems with #1 thrust bearing loose do NOT necessarily relate directly to rod failure etc. The crank can move fore and aft a couple millimeters and the rods are ok with that as long as they get oiled. The fore/aft clearance inside the pistons mean the whole crank/rods assembly can float a lot. Clutch obviously doesn't want any oil. But just because the #1 main is loose for thousands of miles, if the flywheel seal and o-ring are holding up the clutch may stay dry and work fine for quite a while. But every time you step on it, you're jamming the loose #1 bearing into the case and damaging it more.

If I can get these pics uploaded...
A - You can see 3 main bearings in profile with different thrust flanges (always front flange only) Usually .040" thicker or .060" if line bore dia. is also .060" More important than the 27mm figure, is the exact measurement BETWEEN the flanges. Sometimes a case will be "thrust cut" only the minimum amount to clean up the damage. Then the #1 bearing has to be turned on a lathe to carefully trim for width BETWEEN the flanges of .0001-.00015 LESS than width of case saddle for proper crush. Its challenging (but vital) to get it all dialed in.

B - I zoomed in on Max Welton's pic and marked (what looked to me like) a typical shoulder of wear on the case from #1 bearing flange eating into case.


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modok
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PostPosted: Thu Feb 10, 2022 10:57 pm    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

I agree. Very Happy
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virusdoc
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PostPosted: Fri Feb 11, 2022 11:10 am    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

Gotta love resurrecting a 10 year old thread. The OP hasn't even been on thesamba in 8 years...
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Zundfolge1432 Premium Member
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PostPosted: Thu Feb 02, 2023 9:00 am    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

Worth reading all 3 pages
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TDCTDI
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PostPosted: Thu Feb 02, 2023 10:12 am    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

The single port in my car has at least 1/4” of end play. I tried adjusting the shim thickness & quickly found that the slop was between the bearing & saddle (crank bound on the bearing & you could feel the bearing rotate a few degrees until the wallowed dowel pin made contact again.). Since it’s one of the least desirable “H” cases, & the engine ran great otherwise, I said fuq it, tossed it back in & have put over 12,000 miles on it in the last 5 months, all while pounding the shit out of it, with bigger tires. When it dies, I’ll toss another in it’s place.
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KTPhil Premium Member
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PostPosted: Thu Feb 02, 2023 10:29 am    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

With that much play (1/4" yikes!), ignition timing must be all over the map, and I wonder if it will soon allow interference between a rod and the case, causing catastrophic failure. But those old engines were pretty tolerant if left alone, so I'm not surprised you are getting away with it. But it may end with a "bang"!
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TDCTDI
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PostPosted: Thu Feb 02, 2023 10:58 am    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

It was seized from sitting 20+ years, water in the crank case too. Now it’s just a test to see how far it goes.

Yeah, the timing scatter is atrocious. Can’t even set it with a timing light. Advance it until it knocks under load, & then back it off a few degrees.


Oil light only flickers when the idle drops below 600-ish rpm when it’s hunting for idle.
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KTPhil Premium Member
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PostPosted: Thu Feb 02, 2023 12:00 pm    Post subject: Re: Crank End Play, Should I be worried?? Reply with quote

My Type 3 case was worn (though not 1/4") and the oil light started coming on when I pressed the clutch, so it was impending bearing trouble at the thrust bearing. New case, rebuild... expensive! Maybe if I had addressed it sooner I could have re-used my original case, but I didn't and paid the $1K price for that.
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