<VV> Engine building - bearing clearance

Thu Jan 21 17:49:42 EST 2010

All, A .001 under brg. is .001 smaller total. .0005 smaller per half shell. 
Measuring main brg. clearance in a torqued block with brg. shells installed 
is a tricky business. More so even with cheap telescoping guages. You have 
to set the tension on the guage tightning screw the same every time and you 
have to feel the tension of the micrometer sliding on the telescoping guage 
to measure diameter the same every time. The only accurate way to measure 
clearance is with plastiguage or measure the diameter of each crank journal 
in at least two places, better if it's six, with a micrometer, use a 
telescoping guage, (I have found Starretts to be the best) and the same 
micrometer to measure the bare bore with the block halves torqued, then 
measure the thickness of the brg. shells with a special micrometer with 
bullnose jaws. I can't remember the correct name for this micrometer at this 
time. Add the thicknesses of the two brg. shells together, subtract that 
number from the bore diameter, find the difference of that number and the 
crank diameter. That will give you the clearance. To be extra accurate you 
need to measure the main brg. bore in three equadistant places and see if 
the bore is round. Same goes for rod brgs. And you should measure cylinders 
bores in at least six, better if its 9 different places, two or three top, 
two or three middle, two or three bottom.

Jamie
25 years building engines
10 years as a tool maker

----- Original Message ----- 
From: <corvairduval at cox.net>
To: <virtualvairs at corvair.org>
Sent: Thursday, January 21, 2010 3:54 PM
Subject: Re: <VV> Engine building - bearing clearance

I'm also agree that .001 shells add .0005 per shell, .001 total undersize.

I think the reading error is because the crank was not in the bearing
shells when you torqued down the block, hence why plastigage works. The
presence of the crank will affect the crush of the shells.

Awaiting with flame suit on. ggg

Frank DuVal

Original Message:
-----------------
From:  corvair at mts.net
Date: Thu, 21 Jan 2010 14:55:36 -0600
To: hyarnell1 at earthlink.net, bobhelt at aol.com, virtualvairs at corvair.org
Subject: Re: <VV> Engine building - bearing clearance

I am measuring the inside of the bearing bore in a torqued block, using
snap gauges and a micrometer.

I measure the crank, the journal is (for example, and from memory) 2.0985".
I measure the corresponding bore with snap gauge (.001 shells installed),
then mike the gauge, and get 2.0991".

So my clearance is .0006 - too small.

I want .0010 more clearance, so I substitute 2 STD shells instead of .001
shells.

Remeasure, and now the bore measures 2.1011 and clearance is .0026" (pretty
big).

That's what makes me think that a single .001 shell takes away .001
clearance and a pair of them takes away .002.

It's confusing me. Assembling with plastigauge will assuage my concerns.

Les

>
> From: "Harry Yarnell" <hyarnell1 at earthlink.net>
> Date: 2010/01/21 Thu PM 02:37:08 CST
> To: <corvair at mts.net>,
> <bobhelt at aol.com>,
> <virtualvairs at corvair.org>
> Subject: Re: Re: <VV> Engine building - bearing clearance
>
> What  are you measuring with? Plasticgage is the only way I know of.
> Measuring with mechanical calipers gets you close for the crank. Forget
> about measuring the bearings with calipers...
>
>
> Harry Yarnell
> Perryman Garage and Orphanage
> hyarnell1 at earthlink.net
> ----- Original Message ----- 
> From: <corvair at mts.net>
> To: "Harry Yarnell" <hyarnell1 at earthlink.net>; <bobhelt at aol.com>;
> <virtualvairs at corvair.org>
> Sent: Thursday, January 21, 2010 3:08 PM
> Subject: Re: Re: <VV> Engine building - bearing clearance
>
>
> > That's what I thought too, and it's why I'm scratching my head. It's
hard
> > to measure the thickness of the bearing to know for sure.
> >
> > I swap ONE shell, and my clearances are good - added .001 by swapping
one
> > shell.
> >
> > I will plastigauge as a last step but this is confusing me.
> >
> > Les
> >>
> >> From: "Harry Yarnell" <hyarnell1 at earthlink.net>
> >> Date: 2010/01/21 Thu PM 01:56:59 CST
> >> To: <corvair at mts.net>,
> >> <bobhelt at aol.com>,
> >> <virtualvairs at corvair.org>
> >> Subject: Re: <VV> Engine building - bearing clearance
> >>
> >> I thought that a .001 undersize bearing was the TOTAL, not .001 for
each
> >> shell .
> >>
> >> Harry Yarnell
> >> Perryman Garage and Orphanage
> >> hyarnell1 at earthlink.net
> >> ----- Original Message ----- >
> >> > Am I correct that a .001 US bearing is supposed to take away .001
> >> > clearance for EACH bearing shell (.002 total if you use one on each
> >> > side)?
> >> > That's what my measuring looks like.
> >> >
> >> > I have a nice .0010-.0016 across all four bearings now, all .001
except
> >> > for 1 side STD in #2 and 1 side STD in #4.
> >> >
> >>
> >>
> >
> >
>
>

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