The Ford Barn

smurph · 04-09-2019, 04:23 PM

I need some help from the FordBarn experts.

My 1929 “A” has developed an engine knock.

At idle I can hear a steady tapping of the valves which sound normal.

But, there is also a steady knocking sound at idle, which stops as revs increase to 800-900rpm, and then resumes again as revs increase to 1500ish.
I would estimate the frequency of the knock at idle at 3X per second, and the
frequency increases at higher revs.

At idle, if I short out #2 spark plug the knocking sound gets louder. This does not happen when #’s 1,3, and 4 are shorted out.

I’ve compression tested all cylinders and they all read the same at about 60-62 lbs.

I think the electricals are working OK. I was having carburetor problems which I’m not sure are fixed yet, but I think that is separate from the knock.

So, I would appreciate hearing your thoughts on what the underlying problem may be.

Thanks in advance for your inputs.

04-09-2019, 04:23 PM	#1
smurph Senior Member Join Date: May 2010 Location: Cold Spring Harbor, NY Posts: 102	Engine Knock Diagnostic Help Needed I need some help from the FordBarn experts. My 1929 “A” has developed an engine knock. At idle I can hear a steady tapping of the valves which sound normal. But, there is also a steady knocking sound at idle, which stops as revs increase to 800-900rpm, and then resumes again as revs increase to 1500ish. I would estimate the frequency of the knock at idle at 3X per second, and the frequency increases at higher revs. At idle, if I short out #2 spark plug the knocking sound gets louder. This does not happen when #’s 1,3, and 4 are shorted out. I’ve compression tested all cylinders and they all read the same at about 60-62 lbs. I think the electricals are working OK. I was having carburetor problems which I’m not sure are fixed yet, but I think that is separate from the knock. So, I would appreciate hearing your thoughts on what the underlying problem may be. Thanks in advance for your inputs.