i have a 400m in my 1978 4x4 truck it had a faint knock to it around 2500rpm or more, and a bad vacuum leak, well after about 2 months of dealing with all this, i finally pulled the motor out, the vacuum leak was caused by someone pinching the ground strap between the intake and block. as for the knock i thought it was a broken flexplate, that turned out to be fine, after pulling the timing chain cover off, i found that the chain was about to fall off it was so loose, i could almost pull it off except 1 tooth was hanging up on it, i had bought a rv cam for it also, when i pulled the old one out, it had 3 flat lobes on it. could this have been causing the knock i was hearing? also underneath the intake is a flimsy metal tray. is it neccesary to put this back on? do i need a new one? or can these be re-used?
yes... to the chain knocking. if it was, there should be a worn spot on the inside of the cover. ...frank...
there isnt really a cover, the chain is recessed iton the block and it has a flat steel plate that goes over that
I may be wrong, but normally when a chain is loose enough to make noise, it sounds more like an old 6.9 IDI diesel engine idling than a "knock". When I hear the words "knock" and "400 Ford" (or any other Cleveland based engine) I immediately think of main bearing problem. Seems to be common...anyway, yes a chain will rattle. Had a 302 once that was so loose (like what you describe) it sounded like a idling diesel V8 engine.
