Compression Test

[vickiw106 1]

Hi after changing my engine (the old one was a smoker) I have installed and recently reconditioned bottom end with my new recondition grp a head.

 

The new engine is now smoking even more, so I decided to do a compressions test the result where as from the gearbox side 140,140,110,120 the engine was cold is this ok or am I looking at a ring or liner problem.

 

I have asked the company that recond my head and they said the smoke maybe from some oil getting into the exhaust system from the old engine (but im not sure it’s worse than before)

 

Any help/advise would be appreciated

 

Many thanks

Ian

[woodsy 0]

Maybe worth putting some oil down plug holes and rechecking the 2 lowest ones, if it increases by fair bit it could be rings.However the garage is right in that it could be exhaust got oil in.I done fair few headgaskets etc and if old motor was smoking like a train the oil gets stuck in exhaust and takes a good few miles to clear.

[ALEX 98 1 Cars]

Are you doing the test with the throttle open?

Those results are quite poor!

[quagmire 0]

Who reconditioned the head?

[vickiw106 1]

Are you doing the test with the throttle open?

Those results are quite poor!

 

no just screwing the compression tester into each spark plug whole and turning the engine over for 10secs, not sure that the battery was full charged, seemed to be turning over slowly as there where no plugs in.

 

Who reconditioned the head?

 

a company called willenhall engine centre

[2-Pugs 57]

Pretty sure you should have much more pressure than that. I am happy to stand corrected but I am sure I usually get something like 12bar of pressure on a good engine which equates to about 175psi. So to me your compression seems low on all cylinders. Unless you have some kind of intentional or unintentional low compression engine setup?

 

I would also hazard a guess that the head gasket is leaking between cylinders 3 and 4 as their compression is even worse.

 

As for the oil in the exhaust, I am not sure about that, I would say they are trying to fob you off.

 

Like Alex said make sure you hold the throttle open when you do the test, although I still wouldn't expect it to make that much difference. Running the test with all the plugs out is a good idea, as it'll spin over more easily, just make sure you take out the fuel pump fuse to prevent petrol being pumped in.

 

Who put the engine together? You or them?

 

The result seems surprising if everything is new or reconned, what about valve timing, is that all ok?

[vickiw106 1]

Pretty sure you should have much more pressure than that. I am happy to stand corrected but I am sure I usually get something like 12bar of pressure on a good engine which equates to about 175psi. So to me your compression seems low on all cylinders. Unless you have some kind of intentional or unintentional low compression engine setup?

 

I would also hazard a guess that the head gasket is leaking between cylinders 3 and 4 as their compression is even worse.

 

As for the oil in the exhaust, I am not sure about that, I would say they are trying to fob you off.

 

Like Alex said make sure you hold the throttle open when you do the test, although I still wouldn't expect it to make that much difference. Running the test with all the plugs out is a good idea, as it'll spin over more easily, just make sure you take out the fuel pump fuse to prevent petrol being pumped in.

 

Who put the engine together? You or them?

 

The result seems surprising if everything is new or reconned, what about valve timing, is that all ok?

 

i put the engine together, the same way as i have put all xu engines together without any issues, and the valve timimg is bang on standard setup.

 

i am going to try it today with what i know as a highly charged battery and with the throttle open as see what i get then.

[dcc 855]

is this a turbo lump?

[Anthony 1,003]

What does that compression tester normally read on a known "good" engine? I've found the accuracy of compression testers varies significantly, especially on the cheaper testers. That said, two of the cylinders are obviously low compared to the others regardless of the actual figures - I normally say that 5% difference is normal and upto 10% is acceptable, but they're well outside of that.

 

As said, a little oil down those two bores and re-test to see if the resutls dramatically improve.

 

Also, you really shouldn't need to spin the starter over for 10 seconds when doing a compression test - 2-3 seconds should be plenty for a healthy engine to reach virtually full compression on the gauge, with the majority in the first couple of compression strokes

 

seemed to be turning over slowly as there where no plugs in.

How slowly was it turning over? You really need the engine to be cranking over at a half-decent speed to get a sensible compression test result.