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I put together my bottom end on my 351C today. I plastiguaged the mains with .001 to .003 but then realized that the clearance on my engine is .004 to .010. with the other plastiguage my measurement came to .0015. would using the different plastiguage make a difference, or are my specs wrong. I am stumped on this one.
 

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WOW ... .004 to .010 ... that's huge


Generally you are looking at .0025 to .003 with .004 being too much ... If you are building a straight hot rod race engine you could go bigger ... but longevity will suffer.

.0015 is way too tight though by about any standards.

Infact .002 is too tight


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Larry Madsen
Las Vegas Nevada



<font size=-1>[ This Message was edited by: MonsterMach on 5/14/02 12:54pm ]</font>
 

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By different plastigage, do you mean that each one is from a package of the same color, or that one is one color and the other is from a package of another color or even from another manufacterer? The plastigage that I use is made by Perfect Circle (Dana Corp.) and the green is for .001" to .003", red is for .002" to .006", and blue is for .004" to .009". The scale varies for each one. The 72 Ford Shop Manual lists main bearing clearance for a 4V cleveland as .0011-.0028" I used .0025" when I built my last cleveland. Glad to see that you are checking the clearances yourself and not just throwing together whatever the machine shop gives you. Good luck, Tom
 

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that's why I dont like platigage--too easy to screw up. I like it plain and simple--a few micrometers. Eliminates all guesswork.
 

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Plastigauge is clearly not the most accurate method of nailing these clearances down to a "Knats ass", but it serves well to indicate if things are in the right neighborhood or not. For those of us that don't own and more precise instruments and the additional accessories needed to insure their accuracy it's a great and cheap tool.

I used plastigage just this week ... It indicated too tight of clearances on my mains ... I took the stuff to my machine shop where they determined the plastigauge was pointing in exactly the correct direction. Their measurements indicated the main caps had been bored too tight . They then re-bored the mains and got the clearances right ...

All because I used "Plastigauge" to make an initial determination.
 

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A lot of people give plasticgage a bad rap but it does as it is intended. I usually check my race engines with it even though I have a set of expensive tenths mikes.
 

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I recently picked up a 0-6" set of mikes from an outfit on the west coast. They are made in China but look and function great. I checked the supplied standards against the Starretts at work and they were within 1 to 2 ten thousandths. For $120 I think it was a great investment. I have a set of Starrett telescoping gages for the inside measurements, but if this place offers telescoping gages of the same quality as their mikes, that would be a better deal.If anyone is interested in where I got them let me know, I just didn't know if I should give the place a free plug on here or not.
Danny
 
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