plasti-gauge use question

Ray · Oct 23, 2011

When checking bearing clearance on a crankshaft should plasti-gauge be used dry or oil the journals first? Thanks.

Dick L · Oct 23, 2011

I always have mine lubed and the crankshaft rotated with the caps tight before checking with the plastigage.

Bob Huntress · Oct 23, 2011

Dry. Torque the bearing down and then loosen it and hold it to the gage on the package.

Bob Huntress · Oct 23, 2011

If you suspect that the bearing is out of round, you could just c heck it in multiple spots, but by turning the crank during the check, don't you get reading that indicate a closer fit than there actually is? It would be like a wiping effect across the plastigage. When you torque the bearing, it should push the oil out from the plastigage, yet, if the oil is not pushed away, you would also get a false reading of to close.

Robert in Md. · Oct 23, 2011

Question< I have some plasti-gauge that is 30 years old. Is it still useable or does;t it get brittle and hard?

pete 23 · Oct 23, 2011

Use it dry, do not turn even a little bit. And, if you are checking main bearings with engine installed, you will have to support the crankshaft or get a false reading also. Also, plasti-gauge must not be real cold. I prefer using different thickness of shim stock. Paper or brass.

pete 23 · Oct 23, 2011

Use it dry, do not turn even a little bit. And, if you are checking main bearings with engine installed, you will have to support the crankshaft or get a false reading also. Also, plasti-gauge must not be real cold. I prefer using different thickness of shim stock. Paper or brass.

Cliff Nelson · Oct 23, 2011

Dry. Oil will dissolve the plastigage causing it to be inaccurate. As stated earlier do not turn at all as it will "smear" and give false reading. In answer to the age question it deteriorates over time which makes it inaccurate. If you are going to take the time to do it spend the $2 on a new piece of plastigage.

Dick L · Oct 24, 2011

Again, I oil the main bearing inserts as I install them. I put the the crankshaft in, set the oiled caps on the crankshaft with proper shims if called for from prier measurements and snug them down. I rotate the crankshaft checking the thrust, Torque one cap at a time and rotating the crankshaft after torquing each cap.
Pull one cap off and lay the strip of plastigage on the top of the crankshaft, replace the cap and torque, remove cap without moving the crankshaft and check the plastigage width. You will not have enough oil to after torquing to change the reading.
You sure do not want to be turning the crankshaft without lube on new bearings while in the process of assembly. You do want to check crankshaft assembly by turning the crankshaft.

ASEguy · Oct 24, 2011

I always check mine dry and at room temp. Do not turn the crank when checking. There should not be any need to turn the crank since the journals were mic'ed for actual diameter, taper and out of round previously. Gerard

Alont · Oct 24, 2011

I have so far, never used it,but straight from the horses mouth:-

http://www.plastigaugeusa.com/how.html

I really don"t know if this helps

Alont

Brian Jasper co. Ia · Oct 24, 2011

Always use plasti-gauge on a dry journal/bearing. Oil will dissolve it, will also give an inaccurate reading with oil.

Dick L · Oct 24, 2011

I was instructed in the 1950's to never put a crankshaft in a block on dry bearings and to never put a rod on the crankshaft on a dry bearing. Rebuilt my share of engines over the years and this is the first I have ever heard of doing so. I was also instructed to rotate the crankshaft to feel for a possible tight main or rod so as not to have to spend the time for taking it back down because of not checking.

Must be a bunch has changed over the years.
I think I will stay with what has worked for me for 50 some years. I will still flood the new bearings with oil before letting something touch them including my fingers.

pete 23 · Oct 24, 2011

I doubt that anyone would argue with you about oiling the bearings upon installing them. I think the real question was if the bearing you are checking for clearance should have oil on in the spot you are using the plastigauge. As you have to remove the cap to check the platigauge you then just apply oil again when putting the cap back on, and of course turn the crank as needed for checking.

Dick L · Oct 24, 2011

When someone asks a question like above I assume that they do not understand the details that could cause damage to new bearings. I could care less about what others do, its there money but I do not want someone that asks a question like above to wreck a set of new bearings thinking they should install a crankshaft dry. That is what I get from above though.
People that say that oil will desolve the plastigage when checking has never done it. I have never soaked it in oil for a length of time to check that but laying a strip on an (oily) surface (not oil bath) will not desolve it in the time you make the check.
I have bought several tractors from people that did not know the details. They tried to rebuild them from advise from different YT boards, They gave up on them and put them up for sale when they couldn't get them running.
After making my point if the fellow wants to take the others advise and put a crankshaft in dry (so be it) He now has two sides to choose from.
A fair Amout Of Pictures Within

plasti-gauge use question

Ray

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Dick L

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Bob Huntress

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Bob Huntress

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Robert in Md.

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pete 23

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Cliff Nelson

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