Engine knock

carolina-bob

carolina-bob

Member
Hey guys I have a fairly fresh, rebuilt 4 years then stored, 35 221 flathead that I fired up a couple of weeks ago. It sounds good when cold to luke warm, a little lifter noise is all, but after getting warmed up there is a definite knock in the engine. I tried shorting the plugs one by one with no change. Once it cools down the knock goes away. I'm fairly new to flatties so I could use some advice where to start looking?
 
top end knock?? lower end knock??....not the clatter of lifters??....could be piston(s) hitting head??...Mike
 
What happens to the oil pressure when it warms up ?
carolina-bob said:
Hey guys I have a fairly fresh, rebuilt 4 years then stored, 35 221 flathead that I fired up a couple of weeks ago. It sounds good when cold to luke warm, a little lifter noise is all, but after getting warmed up there is a definite knock in the engine. I tried shorting the plugs one by one with no change. Once it cools down the knock goes away. I'm fairly new to flatties so I could use some advice where to start looking?
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sounds like a main knock, it comes on when engine is hot and the oil thins out and oil pressure drops, as was ask ealier what is the oil pressure when engine is warmed up? ford is kinda vague on oil pressure its not given at idle, it says for most engines #30 at 30 mph, you might try retarding the advance on the dist and see if the knock gets less and quiter
 
It sounds like its upper engine but I'm not sure. Oil pressure is good - it pegs the original gauge when its hot. I'm thinking maybe wrist pin or ???. The engine is an original factory rebuild that I got still in the crate in 64. It was put in the car in 70-71 run for a short while then the car was stored for 30 years. I pulled it down during frame off, pulled the pistons, 1 was stuck slightly and needed to be replaced - broken land. I'm getting ready to drop the pan and take look. I know I torqued the whole bottom end when reassembling, but I'll check it again when I get it opened up. Thanks
 
if its in the fast reciprocating parts it should respond to shorting the plugs .while holding the piston ,A wrist pin should hold the rod from falling under its own weight .
 
Someone mentioned clearance issues between the head and the piston. As the parts expand it could be closing the clearance enough to cause the noise.
 
If your oil gauge pegs the needle hot try a mechanical oil gauge as a double check . Were there any rusty spots on the lifters - cam -valve tips ? David J
carolina-bob said:
It sounds like its upper engine but I'm not sure. Oil pressure is good - it pegs the original gauge when its hot. Thanks
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