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Re: pistons

To: "Bowen, Patrick A. RP2" <jak0pab@jak10.med.navy.mil>,
Subject: Re: pistons
From: "James Carpenter" <james.carpenter@jccsystems.swinternet.co.uk>
Date: Wed, 21 Apr 1999 22:59:26 +0100

>OK, planning a rebuild on my engine and a couple questions come to mind.
>what size are stock pistons, and how do I determine if the are .10 over .02
>over, etc.  What is the best determination to see if pistons are reusable
>in an engine rebuild!

If you can feel a lip arround the top of the bour after a decoke you need a
rebour.  If so you then need new pistons.  Oversized rings are a big
mistake, these dont make the scirt on the piston bigger, and so the piston
is not held so tight, it moves from side to side.  Wearing quicker.

For the 9:1 flat top type.

Size of pistons if you look at the top of the Stanpart pistons they will
have stamped on them the over size.  They will also be a type mine were F.
Anyway basicly this letter tells you more precicely what

The new pistons in my car are made by "Hepolite", I took the engin to a
machine shop, the supplyed me with the correct pistons and bored the engin
to the size.  I think I am .02 over size.   Anyway they were brand new,
althogh the set cost me £100 ish.  Rimmer could get them cheaper £80 but
taking into account postage, and they did not have any, it worked out the
same.

I would be causious about the TR6 ones, is the distance between the top and
the con rod pivot point the same.  1300 Spitfires this distance was bigger.

The other advantage with getting the shop to supply them is they may be able
to match the weights  of the pistons swapping them with ones in stock, if
not even lighten them!

When I asscembled the engin I made a simple set of scails and compaired
weights of all the con rods.  I then did the same for the pistons and gungon
pins.   With that information I was able to match them all together so that
each was of an equal weight.  This is much cheaper than profesional
balanceing, but you do go some way to the end result.



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  • pistons, Bowen, Patrick A. RP2
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