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 Post subject: crank shaft end play
PostPosted: Tue Sep 20, 2011 3:32 pm 
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hey guys got a bit of a problem messured my end float for my engine so i can get the flywheel on but have found i have .50 mm worth of end float with no shims it seems the only shims i have are .24, .26, .30 way to big as it sits tight,a sollution to my problem or what shims are needed or should i say available so i can get it to the required amount
cheers
stevo


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 Post subject: Re: crank shaft end play
PostPosted: Tue Sep 20, 2011 6:25 pm 
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I'm guessing but if you have 0.50mm movement in the crankshaft and you have a .24 and a .26 shim, why not use them both?

kevin


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 Post subject: Re: crank shaft end play
PostPosted: Tue Sep 20, 2011 6:34 pm 
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Bingo!!!!^^^^^^ if u need right on .050 but u should be right around .003-.005 if I rem...to tight and no oil can get in

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 Post subject: Re: crank shaft end play
PostPosted: Tue Sep 20, 2011 6:44 pm 
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.50 minus .50 equals zero, that would be bad. You're after ~.1mm (about .004").

If the crank isn't 8-dowelled, just add a metal gasket between it and the flywheel. That'll add .3mm, you should be able to set the float properly then with three of the thinner shims.
Or, take the flywheel to a machinist and have .30 to .35mm taken off of the thrust surface.

This problem is most-often encountered on reground crankshafts, when the machinist has taken the extra-diligent step of squaring off the snout of the crank (and removing any raised burrs surrounding the dowelpin holes). Unfortunately, shortening the crank this way makes it harder to establish correct end-float unless the flywheel thrust surface is also cut, or you "cheat" by using a gasket or fitting only two shims instead of three. Note that there is NOTHING wrong with using only two (or for that matter, four) shims if you must. Those who subscribe to the "3 and only 3 shims" dogma have their heads up their arses.


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 Post subject: Re: crank shaft end play
PostPosted: Wed Sep 21, 2011 3:25 am 
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thanks mark ill be talking it to a machinest tomorrow in regards to this cheers for your help
many thanks stevo


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 Post subject: Re: crank shaft end play
PostPosted: Fri Sep 23, 2011 7:34 am 
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Location: Brooksville,FL
One thing you may also want to watch out for after you get the crank turned is that when you install your seal make sure you recheck your endplay. On my engine I got everything set and once i installed my seal I lost all endplay, and that was with brand new crank and flywheel. Just wanting to give a heads up. Not sure if that is a common thing or not. Also I was running dual seals, not sure if that makes a difference but worth noting.


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 Post subject: Re: crank shaft end play
PostPosted: Fri Sep 23, 2011 12:29 pm 
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The seal should have no effect on the endplay, if there's an interference issue there the seal's too thick or not installed far enough. A stock seal lives below flush; normally a stock flywheel won't drag on the seal so long as it's flush (not standing proud past the case).
If you use a gasket between crank & flywheel (mandatory on early pre-O-ring engines) it affects the endplay, by approximately .012" for the metal one and ~.008" for the paper. The same thickness gasket must be present when setting the endplay as upon final assembly.


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 Post subject: Re: crank shaft end play
PostPosted: Fri Sep 23, 2011 12:45 pm 
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I didn't know that there is a different flywheel for dual seals. After looking at them side by side I noticed the curve where the seal rides is cut further back. Been there, had that problem. I don't think that the amount that he is having cut off will be enough to effect a single seal but could effect a dual setup.


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 Post subject: Re: crank shaft end play
PostPosted: Fri Sep 23, 2011 3:09 pm 
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im havin .37 taken off which is just over min using the shims i have


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 Post subject: Re: crank shaft end play
PostPosted: Sun Sep 25, 2011 1:27 pm 
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marc is right you can use two shims or one for that matter. But the dogma he speaks of is this. In theory the two outside shims (New shims or shims that are in good codition) act as bearing surfaces for the center shim. Shims become warped and should not be used as well as shims that have an imperfect surface. I have a stockish motor that has been hammered at times and after 12,000 miles I installed a new clutch. During this installation I checked the end play, and it is as set as it was when the motor was rebuilt (as measured witha dial indicator), or no significant wear that is measurable at this point. I have never experimented with less than three shims but i suspect (if the engineers at VW are correct) the life of the engine will be shortened, or at least an increase in endplay will be accelerated (kind of the same thing). Now that being said, a non-stock engine will likely have other factors that shorten the life or accelerate the endplay wear much more than a missing shim.


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 Post subject: Re: crank shaft end play
PostPosted: Sun Sep 25, 2011 9:51 pm 
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There's never been any white paper published to explain why three shims are used. In fact, other engines (including Porsche) typically use only one, which makes me question the veracity of the theory put forth above. The only time when there's a significant load on the surface of the shims is when the clutch is depressed, and at that time all the oil's been squished out from between them and there's no relative motion between them anyway. More often than not when you remove a flywheel and front seal all three shims come off together as a unit.
Personally I believe it's for manufacturing and inventory economy. By using three shims the required range of total thickness can be met using only five thicknesses of sheet metal stock, rather than having to produce a single shim in every foreseeable thickness that might be needed.

Shims are made in .24mm and .30mm to .36mm by .02mm steps (approximately .0094", .0118", .0126", .1338", and .1417")
I'll drop the decimals for simplicity from here on.
24+24+24=72
24+24+30=78
24+24+32=80
24+24+34=82
24+24+36=84, 24+30+30=84
24+30+32=86
24+30+34=88, 24+32+32=88
24+30+36=90, 24+32+34=90, 30+30+30=90
24+34+34=92, 24+32+36=92, 30+30+32=92

...and so on up to 36+36+36=108; with a single shim that would mean producing seventeen different thicknesses of shim, and stocking 17 unique part numbers, rather than only five to cover the same range.

I also find it noteworthy that two of the thickest shims add up to the same as three of the thinnest, and that you can also get 108 with one 36 and three 24s - it's as though they chose these numbers to accommodate a much wider range if necessary...that could be interpreted as tacit approval of the use of more or less than three shims.

While we're on the subject of endplay shims, let me again mention that there are two distinct inside diameters (you'd think that after 45 years the word would be out there, but I'm constantly meeting people who don't know this). When the change was made in mid`66 from sealing the flywheel to the crank with a gasket to using an O-ring for the job, a step was machined into the nose of the crank to accommodate the O-ring. Therefore the I.D. of the shims was reduced by ~1mm. Commonly and incorrectly referred to as "12V" shims, these smaller-I.D. ones won't fit a non-O-ring crank (unless it's been turned .040" under). The early, large-I.D. shims will fit on an O-ring crank, but they'll fit too loosely and sling about, slicing through the nose of the crank. I've seen cranks cut clear through to the dowel pins, but even a slight groove is enough to confound accurate endplay adjustment since the shims can snag in it - don't ever use "6V" shims on an O-ring crank.


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 Post subject: Re: crank shaft end play
PostPosted: Tue Sep 27, 2011 2:53 am 
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And I thought I had a good head for numbers.

As always Marc, your knowledge is amazing.

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 Post subject: Re: crank shaft end play
PostPosted: Tue Sep 27, 2011 7:56 am 
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Marc,
Great information on shim thickness. But I never assume the thickness I always mic the shim and I find variation.

to continue playing the devils avocate:

The main issue I see with less than three or more than three (by the way three shims are used to set the end play in compressors and other industrial applications) is the gap created between three shims may be purposful for maintianing oil film, just as it is for other bearings? Three shims will have smaller gaps than two. Altering the number of shims may alter the oil film. A higher volume oil pump may reduce this issue.

Another issue is the rear main is made to hold a shim in place (thrust surface structure) and may not have been intended to be a bearing surface, and I have never seen a flywheel face machined smooth enough to be a proper bearing surface. I believe there is designed to be float between shims during operationd due to oil circulation and they are not intended to be stuck togeather during operation.

Just my 2 cents.

JR


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 Post subject: Re: crank shaft end play
PostPosted: Tue Sep 27, 2011 1:37 pm 
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mulecreek wrote:
...the rear main...may not have been intended to be a bearing surface, and I have never seen a flywheel face machined smooth enough to be a proper bearing surface. I believe there is designed to be float between shims during operationd due to oil circulation and they are not intended to be stuck togeather during operation...
But they will be "stuck together" anytime there's any axial load applied, there's nowhere for oil to get between them (or between them and the flywheel) when the stack's compressed, as when you step on the clutch. Moreover, the thrust bearing face is most assuredly intended to be a bearing surface - the reliefs in it are how oil under pressure establishes the only oil film adequate to isolate the moving parts from the stationary one under load.
I'm aware that it's common to find 3-shim stacks in non-automotive applications, and the explanation you've proposed makes sense as sound engineering - more so in a grease, or non-pressurized oil, environment though.
It may be that influenced the VW engineers' thinking, but note that the Porsche 356 engine which came later, and was derived from the VW design, uses a single shim.


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