Monte Posted July 26, 2002 Share Posted July 26, 2002 I am in the process of rebuilding the engine for my Monte. When I was installing the rods back onto the crank, plastigage told me I only had .001 if clearance. Way to tight. I checked several other rods. Same thing. So I measured the crank journals and rod size with bearings in them. That showed me I had .0025 clearance. That is what I should have had. So started putting it back together. Still at .001 per plastigage. Since I was using a 6" dial caliper ( not the most accurate way to measure clearances ) to determine the sizes, I figured that the plastigage had to be correct. So after discussing with most of my local race buddies, we figured that since the crank was ground under .022 from spec, that somebody must have resized the rods to compensate. We figured whoever did the rods got them a little to tight. Took the rods in and had them resized. Got them back, started putting the engine together and.... still .001 on the rods. Now I dont know what to think. Took everything apart and took everything down to my buddies machine shop. He looks at the plastigage and says "wow". He then tells me that he machined and measured everything and that he didnt think I really had a clearance problem. So we measured the crank and rods again only this time with his quality micrometers. He got just about the same measurements that I got with the dial caliper. He told me I should have .002 to .0025 clearance. He said to me I think your plastigage is wrong. He says I have seen that before. He told me to put it together and see how tight the assembly is to turn. Now I have been around for a while, but I have never heard of plastigage being wrong. So I went home and re-remeasured everything and put it together. When I got done I spun the engine to see how tight it was. It turns perfect!!! Lesson of the story. I should have believed my measurements to begin with. Turns out the plastigage I got was not accurate. I have never run across that before. I wasted 3 days and a lot of time over this. Thought I would let you guys know. Monte. Link to comment Share on other sites More sharing options...
wallaby Posted July 26, 2002 Share Posted July 26, 2002 If you are at peace with what you discovered, then it was not a waste of time. At least now you can sleep at night. Link to comment Share on other sites More sharing options...
Guest Posted July 26, 2002 Share Posted July 26, 2002 quick question was the plastic gauge old or did you just buy it. I know that if it sits out for a long enough period of time it will turn hard and not give a real accurate reading. just a thought Link to comment Share on other sites More sharing options...
Grease Posted July 26, 2002 Share Posted July 26, 2002 plastigauge can go bad if it get old or heated. also it comes in colors.......i think green is the color i use for crank work.is it also possible that you had some for metric measurement ? Link to comment Share on other sites More sharing options...
Monte Posted July 27, 2002 Author Share Posted July 27, 2002 I bought the plastigage new. Now, I cant tell you how long it was on the shelf at the parts store. It was the green plastigage and we were not measuring metric. Monte Link to comment Share on other sites More sharing options...
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