hi. i picked up a 75 244 3 months ago- these things are really excellent to work on. ive got one question. after replacing the dead old motor mounts i notice that the ol' B20F shakes fairly hard-mostly at idle.
is this an inherent trait? are they not counterbalanced well?
not really concerned about it but id love to know if its the usual or not. thanx!

bingo. its the cold start injector seal (vacuum leak it was!). had time to do some head scratching this eve...funny thing is i checked the injector for proper operation and totally forgot to inspect the seal upon reinstall and it cracked being put back in place (it is almost 30 years old after all eh!)
some blue hylomar did the trick till i can get a replacement.
btw, what are you guys fave parts sources? thus far volvopartsdirect.com and fcp groton have been really good ..and ebay of course. thanx again!

You could use the old method of pulling one plug wire at a time to see if it is related to one cylinder. This should give a very rhythmic miss with no other shakes if you pull the right one.

I forgot to ask. Did it start shaking only after replacing the mounts? I've read some about replacement mounts having varying degrees of firmness (durometer).
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Art Benstein near Baltimore

yeah, i noticed it more after doing mounts - i think beforehand that the shake was being transferred into the body a bit condsidering the orig mounts were absoultely demolished.
it is pretty well tuned- injectors spray well and fuel dist. pressure is correct (according to haynes anyway. i know all vacuum lines are solid and i dont hear any howl so i assume there is no vac leaking.
compression is absolutely stellar- 160 (+/- 4 psi) across the board...
thanx for your replies..this board is really a great resource- its good that people love these cars.

Hmmm. Sounds like you've done your homework.

I know nothing of the B20F from experience. Perhaps someone of the 140/160 persuasion can discuss how they might perform compared to the B21 used the following year.

My ears aren't so good since the days of rock concerts and 8-track players, but I never hear vacuum leaks without the aid of a stethoscope. Especially downwind of that fan. Mostly the leaks I'd look for would be cylinder specific, not hoses; typically a chunk missing out of the bottom side of the intake gasket, or bad injector seals. But if you've tested spray patterns, you've renewed the seals and eliminated what I figured was your most likely. My guess is the vibration gets lost as you increase the idle to about 900-1000, right? And I was using "tuned" in the current fashion meaning plugs and wires (probably nothing else nowadays!). Maybe the mounts are really soft. Whose are they?
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Art Benstein near Baltimore

Another possibility with the injected version; one or more old injectors not spraying well at low pressures (idle). If the motor shook when it was new no one would buy the car.

Assuming a tune up has been tried, vacuum leaks corrected, I'd start with compression checks (easy task), then move to pull the injectors and watch them perform into glass jars (bit more work). Then, valve clearance?
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Art Benstein near Baltimore

My b21a moves around quite a bit, esp. when it is first started, but at operating temperature it settles down. Compression and power are good; the volvo guy who did the tests mentioned that a bad cylinder can cause this, but I don't have a bad cylinder. I think the mount motion is actually to do with the safety design of the motor mounting but I don't know where I got that from.
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__Stef; 81 DL wagon B21A SU carb M46 __313k