In a message dated 22/03/01 12:49:08 PM Pacific Standard Time,
owner-mgs-digest@autox.team.net writes:
> Messages there are of two
> types. "I have one of these and it works great, you can really feel the
> extra power." and "You shouldnt do that, the head cant handle it, the Lotus
> pistons are crowned wrong and upset airflow, etc.". The latter always seems
> to come from people who dont seem to have done it.
> So now I throw it to you. I've got the budget for a set of Lotus .040 over
> pistons and rings, and the machine shop is taken care of. I've also got
> money set aside for an Alloy head and will be using one no matter what the
> bore size ends up being.
>
>
I have bored several blocks to destruction in racing related engine
development activities. 1950 is not normally a problem. Anything bigger can
definitely be problematic.
The MG blocks are fairly thick castings, but have variable wall thickness and
I have seen serious core shift. You could end up like one of my blocks -
taken out to 2000, and only broke through to water when it was finish honed.
Short of ultrasonic testing, or starting out knowing you are going to sleeve
the block, I wouldn't advise anything over the 1950 size.
No - pistons. This whole 1950 business came about when someone realised that
Lotus pistons would fit, and that there happened to be a lot of cheap Lotus
pistons around.
Lotus pistons are NOT the right pistons for an MG. This will not stop people
who are too damned cheap (oops, pardon me - thrifty) from using them, but it
should stop anyone that gives much of a damn.
The compression height on the Lotus pistons is too low, so you have to carve
a whack off the block to end up with the pistons anywhere near the top of the
bore when fitted. In doing this you compromise deck rigidity.
These days, you can have forged pistons made up for less than $100 each that
will last forever, have the right deck height, and won't have the
inappropriate valve cut-outs for the Lotus that will tip the engine shop off
as to what a cheap bugger you really are!
You can pay the machine shop off not to tell anyone, but your MG will know,
and won't respect you in the morning.
Bill
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