what should the compression be on a 1989 740 GL with a B230F 2.3L 4 cyln engine?
i rebuilt it about 2 months ago and want to make sure i have good compression.

thanks
-sal

My turbo runs 145-155 but I believe it has dished pistons to lower the compression.

150-160 even on all four . Some difference ok, but shouldn't be any on a rebuild.

Is that all? On my 89' 740 GL B230F that has 292,000 miles on it, I have around 180 PSI on each cylinder. The main bearings are starting to go, though. I'm pretty sure this engine has never been rebuilt.
Steve

I believe the pass/fail spec for Volvo is somewhere around 145 psi, and you're allowed a maxium of 20 or 25 psi between cylinders (off the top of my head).

However, I typically see values in the 175 to 205 range on a healthy B230F engine in my own car and my friends cars.

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 265k miles.
'88 Black 780, PRV-6, 149k miles.

Is this high compression due to carboning of the heads..? I thought nominal pressure values were around 165 ... then again, I am going from memory and this may also be for a turbo.

I had between 120 and 130 taken while engine was stone cold. On car in sig below..
--
Norm Cook; Vancouver BC; 1989 745T 210,000KM

"Is this high compression due to carboning of the heads..? I thought nominal pressure values were around 165 ... then again, I am going from memory and this may also be for a turbo."

I would have to agree with you on that. I have seen a boat load of red engines that only spun up around 150-170 PSI and if I saw anything over 190 I would suspect excessive carbon in the combustion chamber. It does not take a great deal of carbon to elevate the numbers and every head I have pulled had at least .015-.030" of carbon evenly coating everything. It was not too long ago I had a car come through that failed smog due to excessive Nox and it wasn't by just a little bit either, that sucker was pumping it out. We went through the basics and made sure everything was dead nuts and it was all on the money. It was however pumping out 200+ PSI and it had 200K+ on it. Unfortunately the old timer was not willing to spend the money necessary to diagnose it thoroughly so he went on down the road without fixing it.

On a fresh rebuild I would expect to see numbers in the 180-185 range. Mind you that is on a compression test done by the book, warm engine, throttle blocked,open ALL plugs removed, 4 revolutions per cylinder.

Mark

I thought nominal pressure values were around 165

Yeah, I think that's an older book spec that was never updated, and I've seen that number in my Volvo Green Books as well. However, I've yet to see less than 175 in a healthy B230 (even after carbon cleaning). Also, you must perform a compression test on a warmed-up engine (operating temperature) for the results to be valid. The pistons and rings contract a bit when cold and you'll have lower/inaccurate results.

The next time I compression test an engine that I've not done before, I'll try to get some numbers of before & after carbon cleaning. I do the water sipping method (of steam cleaning) to remove carbon deposits from an engine while it's running.