DUHART JOHN wrote:
>
> Hey All,
>
> Well I got the appropriate measure device (Micrometer?) from drafting
> and went to working measuring various engine parts. Here is the
> brakedown
>
snip
> Cylinder Bores 74.68-74.69mm
>
> Cylinder measurements
> #1 Top 74.26mm
> Bottom 74.63mm
>
> #2 Top 74.27mm
> Bottom 74.58mm
>
> #3 Top 74.23mm
> Bottom 74.60mm
>
> #4 Top 74.21mm
> Bottom 74.62mm
>
> #5 Top 74.25mm
> Bottom 74.61mm
>
> #6 Top 74.25mm
> Bottom 74.57mm
snip
> Now for the questions. According to the values in the Bently manual
>my
> pistons are undersized at the top, but ok at the bottom. What is the
> deal with this?
You need to mic the _bores_ at the top and bottom, not the pistons. What
you are looking for is the maximum wear, found around the top of the
ring travel. This area will determine if a rebore is needed.
snip
>
> Also I have an odd piston. Piston 1,2,3,5,and 6 all have their number
> stamped at the top, on the conrod, and on the bottom of the conrod. They
> also have an 'A' stamped on the top of the piston next to the piston
> number. However Piston #4 has 'STD' stamped on the top, a '3' on the
> conrod, and no number stamped on the bottom of the conrod. #4 piston
> also has two wholes on each side near the conrod pin. Also the
> 'S-shaped' compression ring (I think that is the correct name) is not the
> same as on the other pistons. Any clue as to what I am looking at here?
>
My guess is the engine was torn apart before, and a replacement conrod
and piston was used. If you end up reusing the conrods and pistons, you
might just want to think about balancing now, as you are not using the
original factory balanced parts.
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