Compression Test

[Guest Joyrider]

Hi All,

 

I have just come in from the playroom with some concern over my compression test results: 174, 176, 175, 162! I am not sure if this last one is low enough to worry about, but I think it probably is. 2.0 litre pinto by the way. I am now wondering if it could be down to cam follower clearance being wrong, or is more likely to be something a little more serious. My next step will be to check the clearances but after that my experience fades.

 

Any helpful advice would be very welcome.

 

Many thanks

 

Simon

[Guest Space--ace]

Don´t know what you messure in UK..... sorry. But if this is psi then i think there´s no worry about it. Some guy told me 1 bar is still OK ...

This should be a difference from 14.5 psi So check the clearance, maybe you can grinding in the valves to get it better if there is still a problem. All other things can only be visible with head off i think

[Guest Joyrider]

Thanks Space Ace - it is psi so by your reckoning it looks to be on the limit. I will try the clearances and inspect the cam for wear, and if that doesn't help, it will be off to a Specialist I expect.

[agent_zed]

Hi,

think iam correct in saying if you pop a bit of oil (5ml) into the cylinder and try again if the compression is higher you have bore wear if it doesnt change then its the valves. At least you'd know which end you should be deling with then. hth

[Guest Joyrider]

Thanks again.

 

Any further words of wisdom before I wield the spanner?

[Snapperpaul]

Check the Haynes manual for the expected pressure i think it is about 11 to 13 bar and your figures are not far off, cam duration affects cylinder pressure, the more the overlap the lower the pressure.

 

You can crank the engine a few times with the tester in to see the highest pressure, you can also warm the engine up and then do a test as the rings will seal a bit better.

 

I dont think you have a major problem but if you do take the head off, grind in the valves and refit with a Felpro gasket that crushes to 1mm, that will up the compression by 0.5 or skim the head a bit.

[Guest mower man]

Hi re comp test figs I was taught many years ago that a 10% variation was acceptable .By putting a small amount of oil in the cyls as mentioned you will prove where the slight difference is going. Check valve clearance , but would personaly let run at those figs unlike my own which read 175, 175, 25 ,175 no 3piston had lost its rings !!!!. Hope to get it running today HTH MOWERMAN

[Guest Joyrider]

I did the test when the engine was warm and cranked a few times until I got max pressure - so I think I got that bit right. After everyone's advice I'm going to check the valve clearances and if that doesn't help, add some oil to check the cylinder seal and check the cam for wear. Otherwise, it seems it may be best to live with it unless it gets any worse.

 

Cheers all.

[Guest craig030774]

if it runs ok and sounds alright leave alone

 

if it aint broke dont fix it

[Guest Stuart wilson]

I'd be quite happy with those figures, like has been said anything upto about 10% difference is perfectly fine. What made you do a compression test in the first place? have you a problem or were you just tinkering?