How Does my Compression look? 86 V4 Crossflow

[Kebm]

This is an 86- 110 Crossflow. I rebuilt the powerhead myself and would like to know what the pros think about my compression. I spoke to my local boat shop and I felt that he was skeptical because I did the work myself. He said that with a new rebuild I should see between 125-145 PSI compression. As you can see my compression is a bit lower.

These pictures are the cylinders and banks as you are looking at the powerhead from the rear. This Powerhead has Wisco .044 pistons.

BTW?This forum was invaluable while I was rebuilding the powerhead. Thank you to everyone that takes their time to post very useful advice.

 

[rodbolt]

Re: How Does my Compression look? 86 V4 Crossflow

while the numbers shown look low the number spread is acceptable.
could be your gauge calibration.
try another tester or have a leakdown test run. you may wish to break the motor in and retest.

 

[ScottinAZ]

Re: How Does my Compression look? 86 V4 Crossflow

if the engine is cold, and not fully broken in, those numbers arent bad. I would expect them to rise a bit when the engine is at temp, and the rings are fully seated

 

[JB]

Re: How Does my Compression look? 86 V4 Crossflow

Until the new rings are seated compression numbers are completely meaningless.

 

[Kebm]

Re: How Does my Compression look? 86 V4 Crossflow

Thank you for the replies.

I have about 4 hours on the powerhead now. I will retest after the 10 hour break in.

I did try a different compression gauge with the same results.

Rodbolt, Would you mind explaining to me what a leakdown test is?

 

[Joe Reeves]

Re: How Does my Compression look? 86 V4 Crossflow

The starboard bank always has slightly higher compression than the port bank, exactly as your gauge graphic indicates.

Starboard bank shows on both cylinders (exactly even) 105 psi.

Port bank shows on both cylinders (again exactly even) 100 psi.

Looks very good to me. Expect compression to increase as the piston rings seat properly.

 

[kenmyfam]

Re: How Does my Compression look? 86 V4 Crossflow

Agree. Give it a little settling in time and re-test