12 replies to this topic

[widg]

hi got a 1985 1000cc engine which smokes alot when driving. i have done a compression test and have the readings. mine read between 60-70 psi on all 4 cylinders is this good or not? any thoughts what it could be?

hope some1 can help paul

Edited by widg, 30 June 2010 - 07:16 PM.

[Pooky]

The compression ratio figure and the figure you get doing a pressure test are different things. The compression ratio I believe is the difference between swept and unswept area in the bore (the space the piston moves up and down in is the swept area, the combustion chamber and the head gasket make up the unswept area.

Your pressure figures are just a measurement of the pressure in the bore.

[lrostoke]

4 - 4.5 bar seems pretty low though... On the tests I've done on 998's around 12 bar seems about average.

Did you let the engine crank over enough times for the pressure to go up ??

[Dave33]

With the engine fully warmed up you should be around 140psi to 170psi depending on if the compression been altered,
70 psi is very poor,piston rings if you lucky,if not pistons and rebore.
If compression was ok and just smoked a bit it would most likely be valve seals or guides,but unfortunately for you compression is way down.
This is not to be confused with compession ratio(cr).
you did crank it with all plugs out til the gauge stopped climbing i assume?
Dave

[widg]

With the engine fully warmed up you should be around 140psi to 170psi depending on if the compression been altered,
70 psi is very poor,piston rings if you lucky,if not pistons and rebore.
If compression was ok and just smoked a bit it would most likely be valve seals or guides,but unfortunately for you compression is way down.
This is not to be confused with compession ratio(cr).
you did crank it with all plugs out til the gauge stopped climbing i assume?
Dave

ye took all plugs out and cranks til gauge wouldnt go any more

[Guess-Works.com]

That's a pretty low figure...

[QuasiMondo]

Did you run the test on a cold engine?

[widg]

Did you run the test on a cold engine?

no on a warm engine

[majj2]

hi got a 1985 1000cc engine which smokes alot when driving. i have done a compression test and have the readings. mine read between 60-70 psi on all 4 cylinders is this good or not? any thoughts what it could be?

hope some1 can help paul

What mileage has the car done and what colour is the smoke?? These are very low readings but before righting the engine off i would remove the cylinder head.
Badly worn seats,valve stems and seals can cause an engine to smoke alot.

[chlblnz]

hi got a 1985 1000cc engine which smokes alot when driving. i have done a compression test and have the readings. mine read between 60-70 psi on all 4 cylinders is this good or not? any thoughts what it could be?

hope some1 can help paul

What mileage has the car done and what colour is the smoke?? These are very low readings but before righting the engine off i would remove the cylinder head.
Badly worn seats,valve stems and seals can cause an engine to smoke alot.

I agree with majj2. Definitely worth looking at the valve train before starting on the pistons

[dklawson]

If you have access to an air compressor, buy or make a leak-down tester and use it to determine if you have bad valves, bad rings, or head gasket issues.

[greganderson]

i have this same problem, the compression only goes to about 60-70psi

i dont have smoke though, however when i rev the engine it stutters alot :S

[jkjaxor]

probably more like valve seats and valves, than worn pistons and rings, espesialy if your running a leaded head on unleaded.
jack