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Hi everybody:
I finally got to test the cylinder compression after buying my Amazon almost 3 years ago. It is a B18B and the results were:
#1: almost 180 psi
#2: about the same as #1
#3: around 140 psi
#4: about the same as #3
Strange...the first two cylinders showing 180 psi while the last two are around 140?! I added some oil to #3 and the psi was still the same...I didn't bother to add oil to #4 because I'm pretty the result would be the same.
So it seems that the valves are in need of work...are there any other way to confirm other than the oil addition method? I've found some rebuilt B20 heads for sale...they won't work on original-bore B18, correct? The engine in mine is original and never opened.
By the way, all of the spark plugs look pretty good...light rust-colored...not black or oily.
Any advice? Thanks!
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Hi all, especially to those great guys who helped give input to my original posting:
Here is the latest update what I did...I did the compression test again to make sure , including adding oil to the last two cylinders that had lower compression:
#1 - 180 psi
#2 - slightly below 180 psi
#3 - 135 psi (after adding oil, jumped up to over 200 psi...maybe I put in too much oil?)
#4 - 130 psi (similar results as #3 after adding oil)
I must have done something wrong with the first compression test when I mentioned in the first posting that there were no compression change after I added oil in the cylinder #3. I think I may have not added enough oil to seal the piston the way around...anyway, the above results should be more accurate as I tested and retested.
Sad to know that I cannot just limit the head as the culprit to improve the compression of the last two cylinders. But I went ahead and did the valve adjustments. Sure enough, a couple of valves had "minus" zero clearance!
But unfortunately before I could get to finish the whole adjustment, I snapped a valve adjustment screw.
Oh great...guess I will have to wait on finishing the job til I get new replacement...I was afraid the screw would be hard to find, but luckily, after browsing around, I learned it is called a "ball stud" and the Volvo part number for it is #418286. Available at Volvo Parts Web store (of all places for vintage parts!) for $3.65 each. Cheap for a new, OEM screws when I tried comparing prices at other places.
Will update more after I get the parts.
-DS
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"But unfortunately before I could get to finish the whole adjustment, I snapped a valve adjustment screw."
Just as a note--because we've probably all snapped a B18/20 adjuster screw at one time or another (a 6" or less length wrench helps avoid this)----the last shop I worked in did a lot of British sports car work -- we found the screws in MG (1.8 litre motors) rocker arms fit nicely and seem to be of a "harder" less snapable metal. The fault may not even be your own--who knows how tight/stretched someone else left it the last valve adjustment. -- Dave
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I guess intensive experience working on a great variety of car makes would help know which parts can be cross-referenced. At least I am lucky to even find this part online for the B18/20 and that it is new and at a good price for an OEM. Already ordered four pieces to plaaaaay safe!! I didn't even really use a fraction of my strength when that screw snapped...and I was only using a 5-inch two-end wrench.
-DS
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posted by
someone claiming to be John McPhail
on
Sat Sep 15 20:05 CST 2012 [ RELATED]
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I would try adjusting the valve clearances. Other than that, if the car runs OK, I wouldn't worry about this too much. My bet is that adjusting the valves will "fix" the problem. As Walrus said, 180 psi is very good for an engine that old - almost as good as new. Since you are pulling 180 psi in two cylinders, I suspect that the engine is, overall, in above average condition.
Even if, after adjusting the valves, #3 and #4 are lower than #1 and #2, personally I would not bother to pull the head and investigate unless there are other issues with the engine. 140 psi is on the low side but still acceptable.
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The car runs pretty good...some stumbling when accelerating from stop, but otherwise felt pretty strong.
Thanks for the feedback that running on the 180 - 140 psi difference should be ok, but I'm concerned about the imbalance of the two cylinders working harder than the other two speeding up the wear and tear of the engine.
I had already considered having the head rebuilt sometime soon anyway...especially if I do find that valve clearance is not the problem.
-DS
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posted by
someone claiming to be John McPhail
on
Sun Sep 16 01:01 CST 2012 [ RELATED]
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I agree that the imbalance is reason for pause. However, I've had engines (in other cars) that ran very well at high mileage (150K-over 250K) and gave me no reason to suspect there was anything amiss...but when I checked compression (which I do every 30K or so on my high mileage vehicles) I got varied numbers. Double and triple checked and yep, some pretty wide variations between cylinders. But the engines ran well: good power, good fuel economy and little to no oil loss.
My '72 142E had the head rebuilt back in 1999. 13 years and 180,000 miles later (450K miles on the block) my compression is: 150, 132, 148, 136. Note cylinders 2 and 4 are on the low side, although not as much of a difference as what you are seeing.
Since adding oil to the cylinders does not increase your numbers, you most likely have a couple of valves that are acting up. Clearances are off OR the cam lobes are worn. You possibly run the risk of burning valves in those cylinders.
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Thanks John for the assurance that I shouldn't be too concerned about continuing driving with the PSI numbers having wide difference.
About the valves not having enough clearance and/or the lobes being worn out, I also have a theory that one of the the SUs (on the firewall side)might have been running lean for so long and that it caused the valves in the two cylinders on the same side to melt some. You are welcome to debunk that theory but it would make sense that the compression of the last two cylinders have almost exact same numbers.
The original owner I bought the car from said that he had always had problems with the SUs being out of whack for the last several years, including it catching on fire. That must have been from that SU as the plastic screw of its dampening valve was melted.
Those original SUs have very long since been replaced with rebuilt ones, so I cannot test them to support my claim. But does it make sense that each SU is responsible for feeding power to two cylinders on its side rather than distributing evenly to all cylinders?
-DS
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posted by
someone claiming to be John McPhail
on
Sun Sep 16 07:28 CST 2012 [ RELATED]
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I could be wrong, but I think that if the valves melted or burned, you would end up with no compression in those cylinders. I am guessing that either:
a) The valves are not staying open long enough (or staying closed too long) due to a clearance issue or worn cam lobes.
b) There are other wear issues in those cylinders that have nothing to do with the valvetrain. You said that you tried to squirt oil into one of the "low" cylinders and it didn't make a difference, so you did not try with the other one. I would be interested to hear what happens if you try this again, with both of the affected cylinders. If you can rule out the rings, the other possibility is that you have a leak in the headgasket. The can leak compression or leak coolant, depending on how and where they break.
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John, I certainly do hope the valves are the issue, and nothing else. I will squirt some oil in the #4 to see if it is similar to #3. Then take off the valve cover some time this week to investigate more.
Worn head gasket might be possible although the coolant has always remained at the same level and the oil looks good w/o mixture of other fluids. But maybe, just maybe a leak so tiny that only air can only escape? If so,wouldn't I have smelled fumes in the engine bay with the engine running?
-DS
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"But maybe, just maybe a leak so tiny that only air can only escape? If so,wouldn't I have smelled fumes in the engine bay with the engine running?"
Not if you're losing the gasket seal at the narrow spot directly between cylinders 3 & 4. No fumes, no smoke, no nuthin'... just a slight loss of compression in both cylinders, at least early on in the failure process. This is not an unusual failure mode, BTW.
--
Gary L - 142E ITB race car, 73 1800ES
BlueBrick Racing Website
YouTube Racing Videos
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Ah! Didn't think of the possibility of an air leak bridge between the cyclinders. Now that is added to my list. Thanks, Gary.
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The next diagnostic step will be to do a leak down test. You'll need access to a compressor and an adaptor (cheap simple tool) that screws into the spark plug holes. Rotate the motor for each cylinder so the piston is at the bottom of its stroke--valves closed. Connect the air line to the adaptor and listen for where the air comes out---carbs (intake valve)---exhaust pipe (exhaust valve)---oil cap opening in valve cover or oil separator at pcv connection (pistons/rings).
You just never know what you'll find. Personal example--the B20 in my '69 144--ran fine on the street but had run on track days for two years with oil pushing issues (leaks from front and rear crankshaft seals) but still had performance enough to run 100+ mph and easily to redline+ rpm. Performance at a new track in NJ did not come to expectations so at that point I opened it up. I expected to find a broken ring (oil pushing)--found top rings in 3 + 4 broken. My leakdown test indicated other problems as well and the results of teardown showed one intake valve starting to burn (very rare--probably due to high rpm and a bit of carbon stuck on the valve) in cyl.1 and one exhaust seat receding in #2. A valve job with hardened seats for the exhausts and pistons/rings have restored my motor.
Wonder of wonders--the carb fiddling I used to have to do is now a thing of the past.
As for the cam being worn--this could easily result in very high compression numbers as the valves have very little overlap with the standard cams. I've seen 240 across the board in a B18 that had a totally wiped out cam.
If your performance is satisfactory and oil consumption/leakage reasonable I'd just drive it till it really needs attention--start a rebuild fund now. -- Dave
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Dave, thanks for the great idea of doing the air leak test...I do have a compressor.
Great story about your experience with the B20! Thanks for sharing.
Also Interesting what you said about the higher the compression in the cylinders, the quicker the cam lobes wear out...240 psi is quite a lot!! Factory specs for the B18B show compression to be between 170 - 200. For a 45 year old never-opened engine, having it still run within specs is a wonder even though just from two cylinders. Sure hope whatever problem I find is limited to the head.
Will keep you guys updated on what I find out.
Thanks,
-DS
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"Also Interesting what you said about the higher the compression in the cylinders, the quicker the cam lobes wear out" ---not what I said--or meant to say----the higher compression reading (240) was a result of the valves not opening exactly when they were supposed to (opening later--closing earlier) due to the wear in the cam lobes--thereby not letting a designed in "leak" due to overlap to occur. -- Dave
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Dave, thanks for the clarification. I must have overlooked "overlap" as the keyword.
-DS
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Hello,
Have you tried adjusting the valves?
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
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It did cross my mind it might be something related to valve clearance...now I know for sure I need to check into that. Thanks for the confirmation, Walrus3 and Planetman.
-DS
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First thing you should do is make sure all your valves have the proper clearance.
If you find some that don't have much clearance, get them adjusted to 0.018" and test
the compression again. 180psi is really good for an old engine like that.
--
George Downs Bartlesville, Oklahoma
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