Found a knock (I think)

Peter J

Peter J

Well-known member
Hey Guys,
The other day I was driving at a sustained 35-40 when I began to hear an irregular light knock. No power loss, no diff. when changing spark. Went away somewhat at lower rpms. Noise was coming from top of engine so I checked the dist. which was OK. I took off fan belt and it went away. I think it was the fan pully hitting the pump housing because of excess clearance of the impeller at the head (I think).
Anyone run across this before e.g. the "knock" or rattle at higher rpms from the h2o pump?

Thanks as always for any input,
Pete
 
I once had a pronounced knock that turned out to be the fan belt itself and I saw no flaws in it that could be the cause but a new belt fixed it.
 
Thanks!
Was your fanbelt pulling the water pump fore and aft? I have about 1/8" play in my shaft.
Pete
 
Thanks! I figured it was way off. I built it up with some weld the last time I had it out but then I changed heads, duh! How did your rubber belt make it knock I'm curious to know?
Pete
 
I would check the upper underside of the upper radiator hose where the hose goes over the upper radiator neck or outlet. The fan may be lightly hitting the hose at higher rpm. That is what happened to my september 29 . I have only heard of this happening on 28-29 cars, usually in connection with a repro aluminum two blade fan. I ended up slightly shortening my fan. the repro fans are about one inch longer than original. If the fan is hitting the hose you will be able to feel the spot at the upper end of the hose.
 
Purdy,
I have a 4 blade but I went out and checked. No dings or marks but thanks for the idea. I have about 1/4" clearance.
Pete
 
I had kind of a "clicking" knock. It turned out to be the generator pulley which was one that had 4 rivets holding the two parts of it together. The rivets worked loose and it woud give a knocking sound.
 
Thanks Fred,
I checked out the gen. pulley and it seems solid. I do have some "clicking" but that's my lousy valve adjustment. This is just an irregular "knock".
Pete
 
Do valves need adjusting often on Model A's? I had a VW Beetle that needed adjustment every so often or they would get too noisy...we always said, "a happy valve is a noisy valve" though because it is a bad thing to set them too tight.
 
I know you said it was at the top of the engine, but knocks can "telegraph" and sound like there are coming from somewhere else. Anyway, a source of a knock can be when 1 spoke on the crank pulley hits the front cross member - weak front motor mount spring.
 
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