Compression Test

[chrisgriffiths]

Hi Everyone,

Does any one know what the reading should be for a compression test on a 1098cc engine.

Best Regards

Chris

[MarkyB]

Roughly, over 120 psi is good, under 100 psi = head gasket or valves leaking, in that order.

[bmcecosse]

120 is far from good! It 'should' be 160/170 on a HOT engine with all 4 plugs out - and a brick holding the throttle open. So 140 would be 'poor' and 120 is just about the minimum acceptable for a 'run about'. All 4 should be roughly equal - whatever the reading. Any one or two much lower than the others needs investigation. It's worthwhile setting the valve gaps before doing the test.......

[chrisgriffiths]

OK Cheers Folks !

it's much appreciated

[M25VAN]

and a brick holding the throttle open.

I didn't realise how much difference this makes. Just checked mine after fitting a new head gasket and got 125 on the ones I forgot to open the throttle but 165 on all four when I remembered.

[bmcecosse]

It has to be able to suck in air - to compress it!

[M25VAN]

When you put it like that I'm more impressed with the 125 reading.