B18 in good condition but on aggressive acceleration in 1st & 2nd their is a noise that sounds like a fan blade hitting something, but for sure this not actually the case. The noise is inside the motor (not tranny or drive train) but can't duplicate by simply revving motor; must be under load. Not particularly pronounced when motor is cold but as it warms up. Mild acceleration does not produce noise. Running 10w-30 motor oil and thought switching to 10w-40. Help!

Could be a mild exhaust manifold leak. It would make a bit of a "tapping" sound, more audible when under load.

Worth a look.
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A couple of years ago I picked up a '66 544, with a B20. Its a project which I haven't had time to work on yet, but I have started it a few times. It sounds good for the first minute or two, then starts making a strange noise, which I really can't describe, but is not a knocking sound. I'm thinking it might be the cam bearings. Hopefully I'll find out if I ever get time to work on it.

Check your valve adjustment on rocker arm.

I agree with Matt about checking the compression ASAP. Get the major stuff out of the way first.

It might be the timing gear? The gear well give you a fair warning (by way of knocking) for a couple thousand miles before it goes. This is a common issue if you have a stock fiber gear, they typically have around a 80k-100k lifespan. One of my 1800's had a knock when I bought it. The PO pulled and went all through the engine (twice) trying to find the cause of the knock. It's tricky to spot as the gears usually show no visual signs of trouble. If you're within that mileage range, I'd suspect this might be your issue.

Note: I'm coming from a later B20 reference. I'm not sure what type of gears Volvo used in the B18? If it's a steel gear set up, it's most likely not the issue?
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1990 240 Wagon, 1984 Turbo Wagon, 1971 1800E Auto, 1971 1800E 4-Speed

What is your level of experience with older cars? And do you know roughly the build level of your engine (compression)?

Because it sure fits every condition of pre-combustion knock and ping, and if it's really bad, it could totally sound like a spinning thing is hitting a stationary thing.. Could be caused by a variety of things: High compression (from engine build or carbon build-up), ignition timing off, or distributor advance not working properly.

Is this a new thing? Or has it been going on for a while?

Where in Indiana?

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-Matt I ♥ my ♂

Indianapolis area.

Motor mounts are new and tight and fan blade definitely not the issue. Don't think it's ping because don't hear sound pulling up hill under load like as I have experienced with other motors. Had a retired mechanic very familiar with 544's drive and listen and he was stumped. I have suspected the timing gear but have not read a description of timing gear noises. I don't know if a worn gear could move ever so slightly under high speed load to cause the gear to touch something internally and make such a noise.

First--to answer another poster's note--the B18 has the identical timing gear parts as a B20. It's been my experience that a failing timing gear (in that the bond between the fiber gear and its hub is failing) has a sort of hollow cluk,cluk cluk sound--something between a rod knock and a main bearing knock and visual evidence in that when the timing cover is removed there are oil stain streaks spreading outward from the hub/fiber interface. There not much, if anything for the gear to hit within the cover--unless the gear is like crazy loose on the hub and striking the inside of the cover. On gears I've removed due to "knocking", the gear cannot really be moved relative to the hub - the bond failure "knock" happens early in the failure. The installation of a new gear and the subsequent disappearance of the knock has confirmed the diagnosis of a bad gear.
Maybe you can pinpoint the noise by using a stethoscope - or solid bar like a long screwdriver or socket extension and having an assistant slip the clutch out (with the handbrake on and the wheels chocked--or the car's bumper up against an immovable object--wall, tree, telephone pole, etc.) so there's a load on the motor.
As for the possibility of a bad motor mount--I've seen many of the stamped steel motor to mount brackets cracked--which is why I've kept a bucket of them. -- Dave

Yeah, if pulling a hill and no noise at low rpm, probably not knock/ping. The main reason I suggested that was the warm/cold difference you mentioned.

I'm liking timing gear. The larger of the two gears is a fiber gear on a steel hub, and that fiber outer part of the gear will crack around that hub, and eventually break off entirely. Or if you've got a spoked aluminum gear in there, one of the spokes could be broken. Problem there is, I don't see how a failing timing gear would only make noise under load, nor should warm/cold make a difference.

You're sure it's in the engine and not, perhaps, clutch or transmission?

The video posted to youtube idea is a great one... that'd sure help!

Reason I asked where you were is that I'll be in Indiana next week with time to kill. Unfortunately, Indi area is exactly where we will not be :)

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-Matt I ♥ my ♂

...is like trying to identify a smell by description...possible, but pretty hard to get right. Why not try posting a YT video...then posting the link here...it might tax your computer prowess, but it would surely improve your chances of solving the riddle...

Good Hunting

Sounds like a front broken motor mount, which is very common, and under load the fan could be hitting something, or exhaust.