Plastigage life

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Jan 20, 2003 | 01:16 PM

Phideaux

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Joined: Apr 2002

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From: Port Orchard

Plastigage life

Does anybody know if unused Plastigage has a shelf-life? I doubt it, but I'm not sure. If someone knows one way or the other, I'd appreciate the input.

I have a whole bunch that's ~ 10 yrs old and thought it might be smart to ask before using it. Going w/ a false reading on a main or rod journal ain't my idea of a good time.

Thx,
John

Jan 21, 2003 | 05:19 AM

pbrstreetg

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From: Homestead, FL

Plastigage life

Hi-
Nope. No shelf life I'm aware of. I have seen it melt out flat though and then it's definitely garbage. But if it's still round I think it would last forever.

Jan 21, 2003 | 10:33 AM

rabidranger

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From: -

Plastigage life

Plastigague is what $5? I would buy some and not worry about blowin a $5000 engine. Just my .02

Jan 21, 2003 | 11:43 AM

tomw

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From: suburban atlanta

Plastigage life

Ummmh, plastigage is just wax. Precision extruded wax, but wax nonetheless. If it ain't broke, don't fix it. If it is still round, and mashes down cleanly, it should be OK. Now, if you are really intent on clearing this up for those who are curious, please go buy 1 New plastigage. Use it. Use the vintage plastigage. Compare. Please let us know what you find. I'll bet the numbers are just the same....
tom

Jan 21, 2003 | 04:06 PM

rusty70f100

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From: Iowa

Plastigage life

I have a book here, "How to Rebuild Big-Block Ford Engines," by Steve Christ, that says not to use old plastigage. Here is the direct quote from the book; "Make sure it's fresh, otherwise it will indicate more-than-actual clearances." It's near the bottom of p. 118. I wouldn't take the chance using the old stuff. Have fun with your new engine!

Jan 22, 2003 | 06:28 AM

tomw

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From: suburban atlanta

Plastigage life

Dang, now I'll have to wander around the house muttering to myself for a while trying to figure out why 'old' plastigage would indicate more clearance than there actually is. Off the top, I'd say it stiffens with age, and will not compress readily.

HOWEVER. If it is subject to loss of accuracy as it ages, then how do we know that what we get at the store is 'fresh'? Mechanically, it would only deform less, thus the 'narrower' pattern and the indication of more clearance, if it was stiff.

Let me mumble for a while on this, but the need for 'fresh' plastigage just makes me wonder if it is really that accurate anyway..
tom

Hey, wait a minute here. If we were all 'real mechanics' then we would be measuring the clearance with micrometers anyway.... I just use plastigage to make sure that I am within reason on my clearances, not to build anything for other than the street, so old plastigage would work for my use. (I don't have a mic big enough to read journals anyway.) BUT how do we know its fresh? tw

Last edited by tomw; Jan 22, 2003 at 06:33 AM.

Jan 22, 2003 | 08:01 AM

PigFarmer

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From: Charter Oak, Iowa

Plastigage life

My machine shop guys says using plastigage will give in indication of "general" clearances and that the micrometer is the most accurate. Use the plastigage to see if your in the ballpark on clearances and journal taper. If anything comes up suspicious then take it to the machine shop for a good checking with the micrometer.

Randy