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Compression Test
Posted: Sun Mar 09, 2014 5:39 pm
by chrisgriffiths
Hi Everyone,
Does any one know what the reading should be for a compression test on a 1098cc engine.
Best Regards
Chris
Re: Compression Test
Posted: Sun Mar 09, 2014 6:04 pm
by MarkyB
Roughly, over 120 psi is good, under 100 psi = head gasket or valves leaking, in that order.
Re: Compression Test
Posted: Sun Mar 09, 2014 6:14 pm
by 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.......
Re: Compression Test
Posted: Sun Mar 09, 2014 6:31 pm
by chrisgriffiths
OK Cheers Folks !
it's much appreciated
Re: Compression Test
Posted: Mon Mar 10, 2014 1:27 pm
by M25VAN
bmcecosse wrote: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.
Re: Compression Test
Posted: Mon Mar 10, 2014 5:30 pm
by bmcecosse
It has to be able to suck in air - to compress it!
Re: Compression Test
Posted: Mon Mar 10, 2014 6:31 pm
by M25VAN
When you put it like that I'm more impressed with the 125 reading.