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 Posted: 04-19-2005 03:26 pm
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Ron Mau
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While driving my car rather hard, Revved to about 6000 rpms.It developed a loud clattering sound. Now that I have examined the car, I have found that the crankshaft has some play in it, about an eighth of an inch. I don't think that is correct. Am I in need of a rebuild or just new bearings on the crankshaft. What caused this problem so it can be avoided in the future.

Thanks,

Ron Mau

 

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 Posted: 04-19-2005 03:43 pm
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Judson Manning
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Ron,

Are you referring to 'thrust' play?  Have someone engage the clutch...if the crank moves 1/8" forward, you've lost a thrust washer.

Also, what kind of oil pressure at 6000 are you getting?

Judson

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 Posted: 04-19-2005 03:47 pm
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Ron Mau
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Hi Judson,

The oil pressure is at 40- 50 psi, I did notice that the iol pressure at highway speeds did seem a litle lower than last year about 5-10 psi lower.

Ron

Last edited on 04-19-2005 04:31 pm by Ron Mau

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 Posted: 04-19-2005 05:49 pm
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Judson Manning
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40-50psi "normal" for 3000-4000rpm highway cruising for a 907.

by comparison I'm getting 70-75psi at 4000rpm with the 907/910 hybrid, but I also have a x-drilled crank and plain bearings (among other things...)

Low oil pressure will indicate a spun rod bearing which would explain the noise, but it won't diagnose a 'lost' thrust washer.  I'm still not clear if you are referring to the 'play' as fore-aft movement in the crankshaft or something else?

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 Posted: 04-19-2005 06:22 pm
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Ron Mau
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The play is for and aft (front to rear). I checked and the crankshart does move when you push and release the clutch.

Ron

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 Posted: 04-19-2005 06:35 pm
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Judson Manning
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Ron,

The thrust washers are ~1/8" thick and aren't held into the block very securely.  I think you've lost the rear washer.  The bad news is that with every clutch engagement, you're doing real damage to the block.

More bad news, the only way to replace them is to split the block and remove the crank.  If you go that far, might as well turn the crank and install new bearings...assuming the damage to the block is minimal.

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 Posted: 04-19-2005 06:53 pm
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Ron Mau
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This will be my first venture inside of the engine. Where do you split the block. Do I need to take the engine completely out. I need a few specifics, to get me started.

Ron

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 Posted: 04-20-2005 01:04 am
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Judson Manning
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In order to get to the thrust washers the crank has to come out which means the front and rear cover have to be removed, which means the flywheel, clutch, etc. has to come out.

You can do it without tearing the entire engine apart, but you're about 50% there and it's usually worth doing the entire engine if you go this route.

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 Posted: 04-23-2005 01:58 pm
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Gavin
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Ron,

I'd agree with Judson that it's likely a thrust washer issue but given that they run with about 8 thou of clearance, there must be a ~1/8" gap for it to actually get out.
My guess is that the situation has been developing over a period of time. When you get the crank out, you might check the thrust face on the crank as this may be where the damage has occurred - ask me how I know.

Have you noticed that when depressing the clutch, the peddle sometimes drops unexpectedly?

The "clattering sound" is a bit of a worry and I don't think a lost thrust washer on it's own would contribute to this - well, maybe if the thrust is caught somewhere.

Judson, I'm not a JH guy, but could you really remove the crank with the engine in situ?

Last edited on 04-23-2005 02:21 pm by Gavin

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 Posted: 04-23-2005 04:28 pm
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Judson Manning
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No Gavin, I was in a hurry and didn't explain the procedure very well.

In order to get to the crank, not only do you have to disassemble the entire front and rear of the engine, but the entire bottom half of the engine has to come apart.

It is possible to inspect the thrust washers without uncapping the rods, but that's all you can do.  Like I said, once you go this far, it just makes sense to tear the rest of the engine down.

 

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 Posted: 11-16-2015 10:06 pm
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DonBurns
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Does anybody know the thickness of the "standard" thrust washers? They are available standard, +.0025, +.0050, +.0075, +.0100 and +.0150. But if you don't know what "standard" is, how do you know which one you need if the original has worn? Doesn't seem to be in the manual.


Thanks-

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 Posted: 11-17-2015 04:44 am
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Esprit2
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Don,
I've got 4 new ones, measured them with a micrometer, and got an average of 0.0925" (2.35mm)

Lotus = Standard, +0.0025, +0.0050, +0.0075, +0.0100
JAE stocks = Std, +0.0025, +0.0050
DBE stocks = Std, +0.0025, +0.0050, +0.0075, +0.0100, +0.015 (DBE special)

Standard = 0.0925" (2.3495 mm) Measured Thickness
+0.0025" = 0.0950" (2.4130 mm) Calc'd Thickness
+0.0050" = 0.0975" (2.4765 mm) Calc'd Thickness
+0.0075" = 0.0998" (2.5349 mm) Measured Thickness
+0.0100" = 0.1025" (2.6035 mm) Calc'd Thickness
+0.0150" = 0.1075" (2.7305 mm) Calc'd Thickness

Regards,
Tim Engel

Last edited on 11-17-2015 05:19 am by Esprit2

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 Posted: 11-17-2015 08:55 pm
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DonBurns
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Thanks - that's what I needed.

On the subject of the original thread, On my very first rebuild attempt in the late 70's, I tried to set the thrust washer thickness using a feeler gauge instead of an end play meter. Misjudged the taper on the washer and ended up with it being tight. It spun out and destroyed the engine. It's not just a matter of the damage to the block, but all that metal circulating. Should be avoided at all costs. I ended up finding another engine to rebuild and got it right that time. On this my last engine rebuild - I'm letting a performance shop do the whole thing.

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