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Re: [Fot] Con Rod Bearing clearance

To: "steve" <colordog.1@earthlink.net>, "FOT" <fot@autox.team.net>
Subject: Re: [Fot] Con Rod Bearing clearance
From: "Greg Solow" <gregmogdoc@surfnetusa.com>
Date: Fri, 7 Aug 2009 21:53:00 -0700
Steve,
    The standard of .003" clearance was esspecially for stock rods which do 
not stay as round as a Carrillo rod will. Just the same I would like to see 
.002 to .0025" as a minimum figure. We have run engines with as much as 
.0045" with no ill effects, but that is going in the other direction. 
Plasticgage can be used accurately, it is just not the preferred method of 
checking clearance. To use plasticgage, you must be sure to use the correct 
side, and ANY dirt or debrie will affect the results. You must be careful 
not to press down on the plastigage and must let the "clearance" between the 
bearing and the journal do the pressing on the plastigage.
                                                                             
                                    Greg Solow
----- Original Message ----- 
From: "steve" <colordog.1@earthlink.net>
To: "FOT" <fot@autox.team.net>
Sent: Friday, August 07, 2009 1:37 PM
Subject: [Fot] Con Rod Bearing clearance


>I am getting ready to install my newly assembled TR3 motor into my car. 
>Because of a bearing failure at my last event, I thought it would be wise 
>to check the rod bearings with plastigage.
> I put the motor back on the stand, pulled the pan and checked the rod 
> bearing clearance.  Here are the results:  0015,  .00175  .0020, .0015 (in 
> order).
> I thought we were looking for close to .003.  I have read from other posts 
> that Plastigage is not accurate.
>
> This crank is not new.  In fact, it has been racing for 25 years. It is 
> .010 under, and magged OK. The journals have been freshly polished.  Also, 
> this crank has been mated to the same set of Carillo rods for as many 
> years.
> Perhaps these tri-metal bearings from BPNW may be different from the old 
> ones.  I don't know because I didn't plastigage the old bearings before 
> trashing them.
>
> I am thinking about getting a set of ACL bearings and seeing if the 
> plastigage results are different.  Also, I could take the assembled motor 
> to the machine shop and they can re-measure everything there without 
> taking it all apart.
>
> Advice?
>
> ~Steve
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