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10-06-2018, 12:51 PM | #1 |
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Join Date: Jun 2018
Location: Westphalia, Texas
Posts: 27
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29' motor knock when under a load, ideas?
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?
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10-06-2018, 02:08 PM | #2 |
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Join Date: Jul 2010
Location: upstate NY near Mass border
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Re: 29' motor knock when under a load, ideas?
Does it go away when you move the spark lever up?
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10-06-2018, 04:18 PM | #3 |
Junior Member
Join Date: Jun 2018
Location: Westphalia, Texas
Posts: 27
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Re: 29' motor knock when under a load, 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?
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10-06-2018, 04:33 PM | #4 |
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Join Date: Apr 2011
Location: Davenport, Iowa
Posts: 2,083
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Re: 29' motor knock when under a load, ideas?
"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 |
10-06-2018, 04:47 PM | #5 |
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Join Date: May 2010
Location: NC
Posts: 2,975
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Re: 29' motor knock when under a load, ideas?
If not the timing, a loose center main.
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10-06-2018, 09:49 PM | #6 |
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Join Date: Jun 2018
Location: Westphalia, Texas
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Re: 29' motor knock when under a load, ideas?
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10-06-2018, 09:55 PM | #7 | |
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Join Date: Apr 2016
Location: Bellingham, WA
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Re: 29' motor knock when under a load, ideas?
Quote:
http://www.motormayhem.net/wp-upload...ion-Manual.pdf Go to page 10.
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10-06-2018, 10:21 PM | #8 |
Senior Member
Join Date: May 2010
Location: Oregon
Posts: 5,946
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Re: 29' motor knock when under a load, ideas?
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.
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10-06-2018, 10:22 PM | #9 |
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Join Date: Apr 2011
Location: Davenport, Iowa
Posts: 2,083
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Re: 29' motor knock when under a load, ideas?
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 |
10-07-2018, 10:55 AM | #10 |
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Join Date: Jun 2010
Location: Temecula, CA
Posts: 4,066
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Re: 29' motor knock when under a load, ideas?
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.
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10-07-2018, 08:24 PM | #11 |
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Join Date: Dec 2014
Location: langley, wa.
Posts: 642
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Re: 29' motor knock when under a load, ideas?
I thot they Usta say knock on acceleration was rods and on deceleration was mains! Or was it the other way around??
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10-07-2018, 08:27 PM | #12 |
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Join Date: Sep 2012
Location: CA
Posts: 204
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Re: 29' motor knock when under a load, ideas?
opposite
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10-08-2018, 09:39 AM | #13 |
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Join Date: May 2010
Location: Kalamazoo
Posts: 1,656
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Re: 29' motor knock when under a load, ideas?
Is it a heavy clunky knock or a higher pitch, like something in there is trying to break knock?
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10-08-2018, 09:14 PM | #14 |
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Join Date: May 2010
Location: Between Seattle & Tacoma
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Re: 29' motor knock when under a load, ideas?
I guess some people are quite sensitive. Which goes back to why a goof of the month award can be a problem.
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10-08-2018, 11:59 PM | #15 |
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Location: Oregon
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Re: 29' motor knock when under a load, ideas?
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