Dear Bob,
We have bored and sleeved original J type blocks to accept 60 mm pistons,
but I wouldn't recommend it. In two out of two cases the cylinder walls were
cut through to the water jacket, and so we have a wet/dry cylinder liner
situation.
Some of the new J2 blocks have been cast with cylinder wall thicknesses
that allow for 60 mm bores, but you'd have to find out from whoever made
the block what bore they were assuming and what thickness they were
allowing for in the cylinder wall. You might possibly also try ultrasound to
check the existing wall thickness.
The added displacement of the larger bore helps with power output, but
I'd urge you to consider a rootes type blower as a more desirable means
to get more power, assuming your block wasn't cast with 60 mm bores in
mind. We run a J75 Marshall blower on one J2 here, and a J100 on a
C type. My J2 has a short stroke (73 mm) crank for 750 cc displacement
and I have a Marshall J100 I'll be putting on it, which is about all the blower
that engine will likely allow on pump gasoline. The difference in power
between normal aspiration and supercharged is striking.
Best wishes on your J2 engine building,
Bill Putnam
J2 3488
On 16 Sep 2003 at 17:33, Robert Grunau wrote:
> I have a new repro J2 block, present bore is under 57 mm. Can I bore this
> block to accept 60 mm pistons safely?
> Or will my PA engine bore to 60 mm safely.
> Thanks for any information, I don't know much about MMM engines ( but expect
> to learn ).
> Bob Grunau, J-3017, PA-0531
>
> -----Original Message-----
> From: owner-mg-mmm@autox.team.net [mailto:owner-mg-mmm@autox.team.net]On
> Behalf Of Pat Mullen
> Sent: Tuesday, September 16, 2003 1:10 PM
> To: mg-mmm@autox.team.net
> Subject: MG PB Midget Pistons NEW on EBAY
>
>
> Hi all, FYI:
>
> MG PB, Midget Pistons NEW Pre War Item number: 2431803888
>
> 10-day listing
> Ends Sep-18-03 07:49:18 PDT
> History: 1 bid (GBP 29.99 starting bid)
>
> ....Pat Mullen
>
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