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Compression test
Posted: Tue Sep 22, 2026 11:02 am
by moggiethouable
Morning all,
I thought as a matter of course I would attempt a compression test.
The engine is a 1098, bog standard, can anyone tell me what sort of readings in p.s.i. I should look for ?
Thanks.
Re: Compression test
Posted: Tue Sep 22, 2026 11:28 am
by philthehill
150 lb is a good average.
All plugs out - throttle fully open (brick on the pedal) and turned over on the starter to build up to max pressure.
Re: Compression test
Posted: Tue Sep 22, 2026 12:42 pm
by svenedin
150 psi is what I got with my absolutely standard and rather worn out 1098cc. Since rebuild, 170 psi.
Although a useful test, a compression test only tells you what happens at the relatively low cranking speed. I found that although it gave good, completely consistent compression readings, in use especially at speed (e.g 50-60 mph) my worn engine used a lot of oil.
Stephen
Re: Compression test
Posted: Tue Sep 22, 2026 1:56 pm
by moggiethouable
Thankyou people, how much does it matter if the engine is hot or cold?
Re: Compression test
Posted: Tue Sep 22, 2026 2:56 pm
by moggiethouable
My final thoughts are this.
Number 4 cylinder is well down, the rockers are worn, the front oil seal leaks and she does not have yet a lead free head or duplex chain..
So I think I am going to plumb for a reconned engine with everything sorted.
At 98k miles without major repairs I think its time.
She is worth it.