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Re: What to do?

To: Robert Rhodes <aa101479@dasher.csd.sc.edu>
Subject: Re: What to do?
From: "John M. Trindle" <jtrindle@tsquare.com>
Date: Fri, 29 Mar 1996 10:08:04 -0500 (EST)
On Fri, 29 Mar 1996, Robert Rhodes wrote:

> 
>       So, the question is, can I just replace the rod bearings and go 
> on my merry way?  Should I go for the "minor" engine rebuild (rings, rod 
> bearings, camshaft, timing gear) with the engine in the car?  Or is this 
> all a waste of time because if the rod bearings are gone the mains are 
> sure to follow?
>

If you're really set on leaving the engine in the car, it won't be easy 
to get to all 5 main bearings.  The rear one requires unbolting the 
transmission, the front requires unbolting the timing cover (not all the 
bolts, though).  Removing the front bearing holder (what is it called) 
would be pretty tough, and putting it back in even tougher, because of 
the front brace between the wheels.

If your crankshaft is scored or ovaled you're going to have to take the 
engine out of the car.

I'd either do this:

1) Pull the pistons and inspect rings, cylinder walls, and crankshaft.  
If it doesn't look too bad, replace rod bearings with the same size and 
put the same pistons and rings back in.  This will only last a little 
while, depending on the condition of the main bearings and crank.  The 
problem is that the tighter new rod bearings may run drier than normal, 
since the oil will "prefer" to go through the looser mains.  Been there, 
done that with rod bearings and 3 of the 5 mains replaced. 

or 

2) Do it right, and tear it down.  Take the crank, block, and camshaft 
into a good machine shop for measurement and recommendation.  They'll 
want to turn the crank, which makes sense if the rod bearing was really 
"like an old paper fan".  There >will< be damage to the crank at that 
point, if only that it was worn down so much you need a thicker bearing.
 

The problem with the procedure you suggest (replacing camshaft and rings 
along with bearings) is:

1) You're going to have to hone the cylinder walls to accommodate the new 
rings without breaking them.

2) Camshaft bearings?  In my rebuild the machine shop put them in.  This 
lets them measure the bearings for straightness, and thickness if there 
is wear on the cam.  I'm sure you weren't going to replace the camshaft 
without replacing bearings.

3) The increased power from fresh rings will place additional stress on 
the bottom end, which will reveal any weaknesses more quickly.  You 
>will< have a bottom end rebuild in the relatively near future.

In other words, if you mess with camshaft or rings you will need to do 
the vast majority of work you'd need to do for a complete rebuild.  If 
you leave the engine in the car you won't get the crank turned, you won't 
get the block dipped to clean the oil and cooling passages, and you might 
not get to all the crank bearings.

Make your brother pay for the extra work... <grin>

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