I just finished a complete rebuild of the B30A in my '70 164. Out of curiosity, I did a compression test. I got the exact same results on all cylinders; 80 psi on the first puff, 135 on the fourth. Both the Haynes and Volvo manuals show between 142 and 170 psi for ideal compression on the B30A. Is the discrepancy anything to worry about?
Thanks in advance,
Nick

Much thanks to everyone for the advice. I really appreciate the information as few here in Montana know anything about these old Volvos. I will go ahead and break in the rings before I go any further.
Thanks again,
Nick

What Phil said. Compression gauges are really only useful as a comparator, if all cylinders are the same, then all is going well. The best way to judge how well the compression rings have bedded in is to look at the blow-by coming out the tappet cover.

As soon as I get plates on the car I will go ahead and break in the rings (8 to 10 times going 30-50-30 mph on the throttle right?).

Yeah, that's good. Modern rings are pretty good out of the packet, the moly ones are pre-lapped & don't need any real bedding in at all. The bores might glaze up before you get your plates, but it's no big deal as it will come good with a bit of full throttle work in third or top gear.

Compression test numbers are useful for comparison from one cylinder to another, but totally inaccurate for measuring actual compression ratio. Yours are completely even across all the cylinders, so stop worrying about them being a bit lower than what some book says. Sounds to me like you have a perfectly good motor.

How long has it run? Perhaps the rings haven't seated in yet.
Are your valve clearances OK? If they are too tight the valves will leak.
--
George Downs Bartlesville, Heart of the USA!

It has not run too long. I have been spending a lot of time trying to tune it (I am new to HIFs). Most of it's running time has been idling with about a dozen short runs around the college parking lot (It's a college project.). As soon as I get plates on the car I will go ahead and break in the rings (8 to 10 times going 30-50-30 mph on the throttle right?). The cam was broken in and so far I have not noticed any problems in that area. I adjusted the valves right after the test and all were in the .015-.017 range. A little tight, but not excessively so.

I used to run B30 exhausts at 0.018" and ended up with a bunch of cracks
in the seating area of the valves. Some guys say you can get by with it
but I didn't. I would set the valves at about 0.020" and see if that helps
any.
Was the person who did your valves and seats pretty experienced?
--
George Downs Bartlesville, Heart of the USA!

I set all the valves at .021". Yes, the person was experienced. He is a reputable machinist and builds race engines from his garage!
I have had some problems with the SUs. I recently discovered I was running way too lean. Could this factor in? I am still dialing in the carbs. At this point, when I push the "lift pin" on the side of the carb up, the engine stumbles a little bit, but the plugs are a light tan. I also turned the engine over until #2 cylinder was TDC and the top of the piston was a light tan color. Is it still too lean or should I leave it there? The idle has gotten much smoother as the carbs are enriched.

Carbs should not affect compression testing - it is all in valves, rings,
headgasket, and to a degree, valve timing. (At cranking speed a radical
cam has so much overlap that compression readings may be low.)
I would imagine that your cam is not that wild - probably a C cam, right?
And the specs are for that cam.

If your throttle shafts are worn or if you have other vacuum leaks, to get
the carb to tune right with the lift pin at idle, it needs to be too rich
for high-speed running. If the plugs are tan, it is not too rich. Too rich
will make them darker or black.

Did you test the compression again after resetting the valves?
--
George Downs Bartlesville, Heart of the USA!

It is a C cam. I was trying to ask if the lean mixture on the carbs might have caused premature wear and the low compression? The HIFs are completely rebuilt so I don't believe vacuum leaks are a problem.
The same thought crossed my mind after making the post. No, I did not retest. It will be about a week before I can get back to the car, but when I can, I will retest and do a cylinder leakage test.

Worry about having the valve clearance to tight, do not worry about compression testing. This is a Volvo B30, not a honda civic 4 banger that revs up to 10K. It takes close to 1,000 miles to break the engine in, and most of that is for the rings.
Do not pay attention to the speedo during breakin, worry more about going over 3K rpm and make sure the rpms fluctuate a lot. No steady driving. Change the filter after a few hundred miles and top off the oil, don't change the oil yet.
Make sure the instructor knows this is an iron block engine and that rings will take time to seat. Your current numbers are impressive. You did a good job putting it back together. I would give you an A.

Klaus
Much better than my 1975 B30F!!!
--
(V♂LV♂s 1995 854T, 1998 V70R)

100 miles is plenty. Moly rings take one good lap around the block to settle in, plain takes a couple of laps. Chrome rings might take 1000 miles, but you should only use chrome for applications where you can't fit an air cleaner.

No, in fact excess gasoline from a rich mixture washes oil off the cylinder
walls and is much worse than a lean mix.
If driveability is OK, your mixture is probably not too lean.

I'd just drive it for a while and see how it is later.
--
George Downs Bartlesville, Heart of the USA!

Use non-detergent oil at first. It helps the rings to seat. Drive gently, avoid constant engine speeds, keep it under 4000 RPM. Change the oil and filter after 500-800 miles. Switch to 10W30 or 15W40 oil of any reputable brand (I like Shell Rotella, a lot of people swear by Castrol) at this time. Continue the gentle driving for a while, after a couple thousand more miles you can take it to the normal redline.

The rings don't seat immediately. You won't get an accurate compression reading until it has done a few thousand miles.