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Old 14-10-2017, 16:53   #16
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Re: Crankshaft Wear Question - YSE 8.

You could go to an almost 0 gasket thickness with a modern sealant and silk thread for an example.
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Old 14-10-2017, 18:54   #17
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Re: Crankshaft Wear Question - YSE 8.

"There is no reason a good machine shop can't measure the existing relationships between the crank and old brg, measure the new brg and work out the desired shim thickness based on how much metal is removed from the crank.

The amount of metal already removed by the wear can only be estimated but it can be estimated reasonably well. Of course the amount removed by regrinding can be accurate so the total removed will be sorta close."


Just for fun (and, I hope, clarity)...

With some made-up numbers;

Old brg flange thickness, 4 mm
New brg flange thickness, 4.5 mm = +.5 mm

.6 mm clearance with old brg, pre thrust-grinding, +.2 mm grinding =
.8 mm clearance with old bearing.

Since you're adding to (reducing) the clearance with the new bearing, you must subtract the difference between the thickness of the old bearing and the new bearing from the existing clearance. .8 mm - .5mm = .3 mm new clearance with new bearing and ground thrust journal.

Then subtract new clearance from desired clearance to get the shim thickness. .3 mm -.15 mm = .15 mm (.0061) shim.

That's the theory anyway.

Of course, if you can achieve the desired clearance with manipulation of the joint between the end plate and the block, the simplest solution is always the best...

Without knowing more about the process, adding material to the front twshr seems scary to me.
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Old 14-10-2017, 20:25   #18
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Re: Crankshaft Wear Question - YSE 8.

^^ Thanks Jimbunyard, this is exactly how I thought I understood it. Thanks for the confirmation.
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Old 25-01-2018, 18:56   #19
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Re: Crankshaft Wear Question - YSE 8.

Quote:
Originally Posted by jimbunyard View Post
.......
You'd still have the option to make adjustments via the end plate gasket thickness...

Agree with your shop, that rear main/thrust brg is a one-time installation thing...

How bad is the rear thrust journal?

Can you get or have made a thicker front thrust washer? Is there clearance at the back if you do?
UPDATE (for those still interested ).

All bits are back from the machine shop. Critically, about 10 thou was removed from the crank rear thrust face.

On a trial re-assembley with no gasket material between the crankcase and bell housing, the end play measured 11 thou.

Book specs are 6 to 12.5 thou (maintenance limits) with a wear limit of 18 thou.

Therefore current plan to to add a 5 thou shim under forward thrust washer and don't use a compression gasket between crankcase and bell housing, rather use use 518 sealant - this should not add any extra thickness but if it does so, I guessing it would only be say 1 thou. BTW, I measured the gap between the mating surfaces of the crankcase and bell housing and it was < 1 thou using plastigage.

The end result should be an end play of about 7 thou. (11-5+1 = 7). This should allow for a tiny amount of wriggle room.

I can get brass or steel shim in sizes of 2, 3, 5 and 10 thou.

Any idea which is better, brass or steel in this application? I'm thinking steel but this is fairly uninformed thought
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Old 26-01-2018, 14:48   #20
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Re: Crankshaft Wear Question - YSE 8.

Are you able to remove metal from the face of the crankcase or bell housing?

Regards,

Richard
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Old 26-01-2018, 14:58   #21
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Re: Crankshaft Wear Question - YSE 8.

Though it probably makes no difference, I too would go with steel...still interested, would like to see some progress pictures...
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Old 26-01-2018, 17:12   #22
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Re: Crankshaft Wear Question - YSE 8.

Quote:
Originally Posted by boden36 View Post
Are you able to remove metal from the face of the crankcase or bell housing?

Regards,

Richard
Technically yes, practically no. Well, I suppose practically yes, if I threw enough money at it.

Truth be told, I never considered this approach but it would work ($$??).

I will post some pictures soon(ish).
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Old 26-01-2018, 17:13   #23
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Re: Crankshaft Wear Question - YSE 8.

Quote:
Originally Posted by jimbunyard View Post
Though it probably makes no difference, I too would go with steel...still interested, would like to see some progress pictures...
OK, will do so as time permits - maybe a week or more away yet.
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Old 27-01-2018, 02:35   #24
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Re: Crankshaft Wear Question - YSE 8.

Some pictures - sooner than I expected

Next step is make the 5 thou shim and also paint the crankcase, bell housing and head using POR 15 engine paint.

Note the crankshaft has the balance weights removed and the liner is not fitted to the crankcase yet (but a trial fit had it sliding in snugly ).
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Old 27-01-2018, 11:17   #25
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Re: Crankshaft Wear Question - YSE 8.

Wotname-
Folks often ignore this, but while you've got the engine apart and open? Consider porting and polishing the area around the valves, or asking the shop to do that for you. Almost inevitably, having that work done by hand gives you some extra power and economy forever after. The production-line castings are inevitably just made "conveniently" and not optimized beyond that.
FWIW.
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Old 27-01-2018, 11:22   #26
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Re: Crankshaft Wear Question - YSE 8.

You may find that putting it in a mill of the sort that machines cylinder heads is a cheap option if it is an easy set up.

Regards,
Richard.
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Old 03-03-2018, 13:55   #27
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Re: Crankshaft Wear Question - YSE 8.

Update, a 5 thou brass shim has been fitted and the crankshaft, crankcase and flywheel housing reassembled. I used 515 as the sealant.

Interestingly and perhaps unfortunately, the measured end play is now just 4 thou rather than the 6 or 7 thou I was expecting (refer post 19 above). I did measure the shim material as 5 thou so I can only conclude the shim hasn't fully seated nicely between the the thrust washer bearing and the crankcase housing; the brass shim was handout with scissors so may not yet be perfectly flat. I am confident of the measurements made in post 19 so I am disinclined to pull the engine apart to replace the shim with a thinner one (say 2 or 3 thou).

Remembering the manual specification is for a 6 thou minimum gap, I feel the 4 thou gap should suffice at this stage and it will increase once the engine is run.

The downside is that if I'm wrong, I will get rapid increase in thrust bearing wear in the early days (best scenario) or thrust bearing failure as worst case .

Your thoughts are welcome...
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Old 03-03-2018, 15:56   #28
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Re: Crankshaft Wear Question - YSE 8.

If you cut the shim with scissors, the edges will be burred. This should correct itself very quickly when the engine is running.

Regards,
Richard
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Old 03-03-2018, 19:35   #29
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Re: Crankshaft Wear Question - YSE 8.

Quote:
Originally Posted by boden36 View Post
If you cut the shim with scissors, the edges will be burred. This should correct itself very quickly when the engine is running.

Regards,
Richard
Thanks Richard, this is my expectation so I'm hoping it's correct.
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Old 03-03-2018, 21:21   #30
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Re: Crankshaft Wear Question - YSE 8.

Depending on how tight the fit the bearing is in the front housing, the helix of the front gears, and possibly the oil pressure, running may or may not compress the burr. Seems I remember that all the wear was on the rear bearing...

I'd guess that you're alright at .004, but specs are written for a reason...

If the press fit of the bearing isn't too tight, a good rap with a 2 lb hammer and a block of wood on the flywheel end of the crank should be enough to flatten the burrs, or at least see if there is movement in the right direction.

If not, standard notebook paper is about .002"...
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