29' motor knock when under a load, ideas?

Dave1929

Dave1929

Junior Member
My 1929 Tudor runs great at idle and while driving casually. I hear a motor knock when I put the motor under a load like accelerating up a hill and such. Any ideas?
 
I have not tried retarding the spark a bit when it is doing it. I will try that though. What in the motor could be making it knock like it is?
 
"jhowes" is probably correct in his assessment of your engine knocking. I have seen time and time again over the years that Model A guys complain about engine knocking sounds going uphill, but they didn't know they were supposed to slightly retard the timing when doing so. It even states in the Model A Owner's Manual to do so, too. (How many new guys actually read that booklet, anyway? Lots of posted questions here could have been answered by reading the manual FIRST) Our modern cars do this ignition retarding automatically in the distributor, or whatever they call the electrical impulse unit nowadays. But we have to do it manually via the spark lever. A local friend drove up our very steep hills downtown for years at speed without retarding the timing and then finally blew off the top of a piston. Upon inspecting the dead engine, it had been a race between all for pistons as to which one would blow off its top first! A nasty, nasty sight, including the rod bearings. He now religiously retards his timing on those steep hills with his NEW engine. :)
As the engine begins to labor while taking a hill, slightly retard the timing lever until you feel the sweet spot where the engine stops knocking, yet still retains enough power to negotiate the hill. It's there; you'll find it. Yes, you'll slow down some, but backing off the timing under such loads will protect the Babbitt rod bearings from pounding out.
Marshall
 
Well thank you for your insight Marshall. I guess you and I have a different manual because I have never read that. But thank you so much for pointing it out to me that I've not read the "official" Ford Model A manual. Again thank you for sharing your infinite wisdom.
 
My old shop teacher always said spark knock was bearing destruction. I agree that reading and understanding the operators manual is the first thing to do when obtaining a new to you car.
 
Thank you, Dick. I was sure I had read the advice about climbing hills and retarding the spark when I first read the Owner's Manual back in the middle 1960's. I was beginning to worry for a minute here that I had incorrectly remembered that information being present in the manual. Whew! I'm not losing my memory after all! Uh...er...what were we talking about again???
Marshall
 
Any loose main bearing will do that, center is most likely, as Geo. Miller says. Is it noisy on start-up after sitting for several days? That's another indication of loose mains.
 
Is it a heavy clunky knock or a higher pitch, like something in there is trying to break knock?
 
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