Dinomat

Hi Everyone,
I've just purchased a 1981 FB bridgeport 12a with ceramic seals, it has a compression of Front 1-77, 2-80, 3-68 & Rear 1-72, 2-67, 3-69. Is this compression ok and in line with a "good compression" or is it pretty rubbish? motor in need of re-build?
Cheers Everyone!

rxtasy3

iTrader: (2)

moved to correct section as this is a technical question rather than a "how to use the site" question.
really don't want to see compression below 85, 100s is optimal. it may run, but will be down on power and would be a pain to start.

mazdaverx713b

iTrader: (91)

Minimum spec for compression is 85psi per face. You have more than a 20% difference on one face on the front rotor and the rear is well below spec. It would seem to me that the engine is worn and in need of a rebuild.

Dinomat

Thank you very much for your reply, very disappointed in rotary mechanic who said it was fine!

Banzai

iTrader: (13)

When the compression check was done, was a rotary specific tester used or one designed for a piston engine? This can make a difference in accuracy. You should use a Rotary specific one.

mazdaverx713b

iTrader: (91)

Also to add, the engine should be at normal operating temperature when the compression test is performed.