Compression numbers (1 Viewer)

[dkyuss]

First compression numbers are in on my 1981 turbo'd 3b engine with 495,000 kms. Engine history is unknown, possibly rebuilt already?

Spec is 427 psi,
Minimum is 284 psi,
*no more than 28 psi difference between cylinders*

Cyl 1 - 425 psi
Cyl 2 - 390 psi
Cyl 3 - 395 psi
Cyl 4 - 435 psi

All is ok other than the difference between cylinders..... should I be concerned? Things to check or look out for?

Thanks

 

[rustybucket]

dkyuss, I have 480,000 km on my bj60 and the compression is 400,400,400,390.

BTW what does your tail pipe look like? absent of any carbon? My fuel economy is the craps even after doing a fuel injector rebuild. I am looking at having a fuel injection specialist remove the IP and bench check it. Will cost me 200-300 to have the IP removed and bench checked.My tail pipe emits blue and some grey smoke on start up when it is cold. I think your cylinder balance looks fine.Do you know of any shops for rent in south surrey? looking to rent/sub out the shop for my self and anyone else.

 

[dkyuss]

There is definitely some black carbon in the exhaust but not abnormal I dont think. I get some smoke on startup (cold first start of the day) but never see it any other time and I have been looking. Cylinder #4 also has some soot residual in the cylinder as glow plug removal and insertion is very tight compared to the other three. I also just recently adjusted my valves as well. All were about 1/8 turn loose except for cyl #4 which was too tight. I'm sure all of this will play into it all as well. She purrs noticeably smoother after the valve adjustment.

 

[kim]

Those area really good numbers. I wouldn't worry about the difference between cylinders. I think the manual says +- 10 percent.

 

[Freewheel]

I only started noticing cold start problems when one of my cylinders went down to 240 with the rest at 380 to 440. Ran perfectly when warm even with the one cylinder at half compression.

 

[dkyuss]

I didn't have too many concerns as has been running fine (engine wise). I am still base lining and getting comfortable with my old girl... Hope to get out into the back country this summer and this is instilling some more confidence! I appreciate the feedback.

 

[kim]

With those numbers and it being a 3B, rest easy knowing that you have years of use!