engine noise

[grizz]

51 flathead 6 makes a dull knocking sound just before time to shift from low
to second and second to third. I thought it was a bearing noise so the crank
was removed and it only needed a light polishing. New bearings installed.
Its quiet at idle and moderate speeds and when pulling a hill. Has good
compression and starts right up with no smoke. Maybe someone has had
a similar problem? thanks

 

[Tim Brown]

I'd check the starter motor. I'm no expert, but had a similar problem that I chased for a few years.

 

[George/Maine]

I had a chevy 6 and had a knock, had it apart could,nt find anything.My guess one of the connecting rod was slightly bent,Never did find out sold engine.

 

[grizz]

What to check for on the starter motor?

 

[Dee]

It might be end play in the crankshaft?

 

[Russ/40]

Front crank pulley not tight?

 

[grizz]

Ive just noticed the heat riser thermostat spring has almost no tension on
the counterweight. The counterweight is halfway between the up and down
position with the engine cold. It can be moved up or down with no resistance.
If someone has a 6 cyl could you tell me if up is closed or open? I plan to tie it
open to see if this thing is rattleling during higher rpms. thanks