In a message dated 4/17/03 3:48:23 PM Pacific Daylight Time,
owner-mgs-digest@autox.team.net writes:
> The 1950cc engine is an 83mm bore. which is considerably more than .060, if
> I'm not mistaken.
>
Yeah - like double that. And I corrected the header line - can't anyone spell
any more? Boreing indeed! ;-)
> The pistons for sale by Moss and VB are, I believe, repurposed Lotus
> pistons which require the block to be shaved as the pistons are too short.
> This causes problems with valves fouling the block and requires even more
> work to reshape the valve clearance "notches". And this often (always?)
> results in a compression ration which is very high, making pump gas a
> crapshoot.
>
I do not like using Lotus pistons - you have to shave too much off the deck
to get to even stock compression. The valves are no more likely to hit the
block when it is shaved than when it isn't, excepting out the late blocks
that have a relief cut for the intake, and you can always cut that a bit
deeper. Probably have to anyway if you are going to use a higher lift cam.
How long do you plan to own the engine, anyway. Don't be cheap - buy correct
pistons with the proper compression height and don't bother with the Lotus
left-overs. BTW, use of Lotus pistons will NOT result in high compression
unless you shave the head (not the block).
Bear in mind that shaving the head OR the block will throw the rocker
geometry out and cause accelerated guide wear (unless you do other stuff I
won't get into here).
> It also is not possible on every block, as many will go right through to
> the water jacket.
>
I think that _all_ blocks will easily take .080 - you could buy factory
competition pistons in that size for the 3 mains (forged, flat top Hepolites
- I use a set in my TVR race car).
Most blocks will take the punch to 1950. I have broken through when going
larger than that, with a block with excessive core shift and thus a cylinder
wall too thin on one side. But for the street, why bother. Use .060 or .080
and be happy.
Bill
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