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MG MGA - Which Twin Cam Pistons?

Whilst I freely acknowledge that this is a poor picture, can anyone hazard a guess which pistons and which compression ratio I might have in my twin cam? It’s been a question unanswered categorically ever since owning the car and ever so difficult to make much sense of it looking down the spark plug hole. The rather grainy picture is from one of those portable inspection cameras. Anyone?
Bruce

B Mayo



Valve cut outs look small to me Bruce, so my guess is Low Compression.

Mark Hester

They are low compression with the curved top and small valve clearances.
Possibly original factory 8.3 CR pistons, but could be aftermarket replacements.
The high compression 9.9 CR pistons look quite different.
See attached image.

Mick

M F Anderson

Thanks Mark and Mick. 8.3/1 it is then! Would prefer 9.9/1 but this engine runs so nicely it's going to be left well alone!
See you at Brooklands for MG Era Day today Mark.
Bruce.
B Mayo

Bruce

??? It's tomorrow - 8th.

Steve
Steve Gyles

Ah! Just testing you Steve to see if you’re awake! Thing is, some of us are meeting up tonight with the MGC crowd for dinner at the Fairmile, Cobham, then overnight Premier Inn there, group breakfast, then convoy of A’s and C’s into Brooklands tomorrow early. So, slightly inaccurate use of “today”!
Now that you live south of Watford, will you be at Brooklands tomorrow? 07802 170135 if you will be there.
Best
Bruce.
B Mayo

This thread was discussed between 06/04/2018 and 07/04/2018

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