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Old 06-01-2004, 09:26 PM
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Plastigage

I have been confused for a long time about the correct way to use plastigage. I am about to assemble an engine and would like to know the correct way to use it.

Do you assemble the bearings dry or with a good coat of oil?

If you use oil, are you measuring the total clearance or just the clearance on on side?

Thanks, Dave

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Old 06-01-2004, 09:36 PM
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assemble dry with NO oil and DO NOT turn the crank.
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Old 06-01-2004, 10:30 PM
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Dave, go ahead and lube your lower bearing, as you assemble just don't lube the top bearings and crank journal, lay a piece accross the journal snap your bearing in place and torque. Yes, it's good advice not to turn the engine over. Measure the squish and scrape if off, lube your bearing and put it together. (If it measures OK, that is.)

Old plastiguage can get dried up and shrink, so make sure the stuff is not a million years old and it's always good to use mics along with plastiguage to verify things if you can.
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Old 06-01-2004, 10:33 PM
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Well, I have used them with oil on both bearings and have found that the plastigauge will displace the oil and read the same. You do want to make sure and lube the bottom bearing.

Chris
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Old 06-01-2004, 10:54 PM
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It seems to me that if you lubed the lower bearing half, the oil would hold the crank up and not give you a true measure of the clearance.

It also seems to me that if you lubed both halves that the oil would hold the crank centered in the bearing and you would only measure half of the total clearance.

?????

Dave
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Old 06-01-2004, 10:57 PM
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How is oil , which is viscous and just sitting on the bearing shell going to hold up the crank? Yes, sure there is a minute film of oil there, but it's not going to "hold the crank up" at least not at any level that you can measure it with a mic.
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Old 06-01-2004, 11:00 PM
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The Plastigauge material pierces the oil film.
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Old 06-01-2004, 11:06 PM
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Quote:
Originally posted by 4 Jaw Chuck
The Plastigauge material pierces the oil film.
Like an arrow, or would it be more like a tongue ring?---OUCH!

Also 4 Jaw, I was wondering if that cat in your Avatar is yours? He looks very pissed, like you just kicked his $%# for digging in the garbage.
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Old 06-02-2004, 12:59 AM
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I allways torque the rods in pairs with shims between the two rods. less chance of the rod moving whyil torqueing.
Just a dab of oil were i lie the plastie gauge to make it easyer to remove. Ya still have to pick away at it with your finger nail to get it off.
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Old 06-02-2004, 02:02 AM
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Quote:
Originally posted by NAIRB
Like an arrow, or would it be more like a tongue ring?---OUCH!

Also 4 Jaw, I was wondering if that cat in your Avatar is yours? He looks very pissed, like you just kicked his $%# for digging in the garbage.
...thats why we call him Rambo.

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