volvo amazon engine compression?

lalababa

Hello everybody! My amazon runs fairly well , has good power, while not ticking over like a clock but I think this is carburettor related as if I make it rich she ticks over like a tractor. I checked the engine compression after running her for 5min. and got 3 75's and one 80PSI. These seem very low as I've read that they shoul be around 150. Is my gauge crap( cheap on amazon.co.uk)? is my engine sooo tired? Is everything infact hunky dory?! Any suggestions? Thanks.

JoeySully

Im no expert but from what I have Heard


It does seem a bit low but there isn't much difference in the figures across all cylinder so that's good. Try adding a teaspoon of oil to each cylinder and redo the test with the engine warmed up. If that improves the compression then it would probably be the piston rings. If it doesn't change 15%+ then check your valve clearances. might not be closing fully?
Don't know anything about these engines but if the valve timing is out then that wouldn't help the compression either.

245

Tell us more:

Is it a B18A/B or D? Or B20A/B?

As previously said, compare with 'wet' compression results. If it increases then it may be valve adjustment or maybe you need to get valve seat inserts and a valve job.

Is it burning oil normally? Any blue smoke on the overrun?

If its a late Amazon, is the crankcase breather setup blocked or getting blocked? If early, can you feel exhaust pulses at the crankcase vent?

What colour are your spark plugs? (at the cylinder end....)

mountain

from haynes manual,
B18A, at 250-300 rpm, 156-185 lb/sq inch, 11-13 kg/sq cm
B18B, at 250-300 rpm, 170-200 lb/sq inch, 12-14 kg/sq cm

hope this helps

lalababa

It's a B20B, theres no smoke from exaust, and no oil usage. A pipe runs from the intake manifold into a T junction one going to brake server (later add on)and one terminates with a small simple mesh air filter. The pipe from the crankcase ventilation runs under the firewall under the car to at least the mid section and terminates in nothing (I guess). There is a little tiny filtery type vent filter thingy on the crankcase ventilation oil trap thing?There is no pipe ontop of filler cap? and oil leaks out here (not a lot), oil leaks out of the rocker cover gasket too(a fair bit). Performance is as good as always.Did a quick compression test on cylinder 1 which was 75psi before and 65 now.I had the engine on for 5 min.s. Maybe I should have it going for longer! Will do a wet test tomo and post. Thanks

245

It all sounds quite healthy. Is your compression guage the push in or screw in type? It might be leaking or maybe just faulty.

Make sure that you do the compression test with the throttle fully open.

Drop over to the Irish Volvo club (www.ivc.ie) if you'd like to meet more like-minded people.

It'll be interesting to see the results of your next compression test

lalababa

Did a dry test and a wet test today after a long run and got 60psi and 125psi??

lalababa

my spark plugs are reading almost nothing at the tip , they remain very very clean not colour at all really, like new.

JoeySully

id get another gauge to be sure.
I think That is a huge difference between wet and dry???

245

The difference between wet and dry indicates that your rings are worn or that your bores or worn (probably both)... Your cam may well be worn too - the lobes towards the front of the engine are more prone to wear on the pushrod redblock engines.

The cleanliness of your plugs is a bit strange - they should be tan with light deposits - sounds like the engine is running lean.

I agree with the previous poster - I'd try to borrow another guage. 60 psi should result in noticeable poor running. The oil leak from the rocker cover may indicate a pressurised crankcase, tying in with the poor compression readings but may just be a tired gasket or a warped rocker cover (many people overtighten them). You can check the rocker cover straightness with a sheet of glass and a feeler guage.