Why is my 200 groaning?

[jamyers]

Odd question, I know...

At anything above an idle, and especially when cold; my 200 goes "grooaannnn" (it really does sound like that, too) every so often at seemingly random intervals roughly a minute apart. If the hood is open you can hear it quite loudly from somewhere in the block between the distributor and the coil, but even with a heater hose I can't pinpoint the location more than that.

While driving around, I can almost feel it as much as hear it faintly. If I didn't know it was there I might not notice (and I'm sure 75% of other drivers wouldn't either...), but it's there. The faster the rpms, the more often it happens.

The engine drives like a champ without overheating...

I'm assuming decent oil pressure because I've had the valve cover off and there's plenty of oil at the rockers and pushrods...and the oil light goes out immediately on startup and will stay out quite awhile after shutdown (key back on)

Both the Duraspark 1 dizzy and the fuelpump (with huge built-in filter) are new...

Ideas? Suggestions? Silly remarks?

 

[JackFish]

Had a heckuva time tracking down a noise, turned out to be a loose alternator bracket bolt.
How old/new is the timing chain?
Maybe a belt slightly out of alignment?

 

[wallaka]

Mine made a similar noise...the alternator nut had loosened sometime in the past, then rusted in place. The alternator fan was loose on the shaft and would vibrate. Took me forever to figure that out. It was weird because the alternator charged and the belt didn't squeal or anything.

 

[Anonymous]

I had a similar noise until I drilled a 1/8 inch hole in the thermastat flange. I was having bad air lock. Sounded like my car had "gas."

 

[pedal2themetal45]

Just a thought
How about power stearing?? I've heard them make a gronning sound when low on fluid.
tim

 

[MustangSix]

A really loose tining chain will slap around the inside of the housing, sounding like a groan.

 

[jamyers]

Good ideas, I'll check them out! Hadn't thought of a loose bolt somewhere, SURELY we got them all tight when we put the engine in there... :roll:

Manual steering, but it does have a/c, which hasn't been on much (yet).

I don't know how many miles are on this engine (it was a freebie), but the timing chain had very little slack and it's got good compression. (My fear is that there's a galled lifter making noise as it rotates around on the cam lobe.)