Engine knocking after storage

U

unsichtbarre

Junior Member
Howdy everybody, my name is John and I am new to the forums.

I've had my 1931 model A for about 10 years, and through that entire period of time it has been very reliable.
Last fall, I went to start it and although it cranked, it would never start. I probably cranked it too much trying to get it started thinking it was just a fuel issue but it never fired or even attempted to fire. I was busy at the time so I didn't even attempt to diagnose the problem but rather left it in storage for the entire winter.
Come the other day, I went to start it and in diagnosis I discovered that the fuse on top of the starter had blown. Easy peasy I replaced it with a 30 amp fuse, and it started right up but had a real bad knock. This surprised me because the last time it ran it was running well and shut down with no sign of a knock at all.
I removed the plugs and scoped the cylinders and saw nothing unusual. I removed the side cover and checked the valves and aside from a little bit more play than I would like to see they all seem to be normal and operating as I crank the engine by hand.
I'm hoping it's not what I think it is, rod knock, and I was wondering if anybody had any ideas of something I should check before dropping the pan and doing rods?
I did read all the posts about knocking here on this forum and others and plan on looking at the timing gear next but am I missing something obvious here? Why would a rod knock develop while sitting in storage?

Thanks,
JB
 
I had a bad knock in mine and the timing gear had a couple of mangled teeth on it. Sounded like #1 cylinder was getting ready to come out of it. I would definitely check that first.
 
Get a mechanics stethoscope and see if you can narrow down the location of where the noise is coming from. If you don't have one of those use a long screw driver and press the handle of that to your ear as you probe around the engine with it.
 
Thanks for all the great replies, I will definitely check the timing gear. I did use a mechanics stethoscope and one was unable to localize the noise.
In checking the timing gear would it be sufficient just to remove the side cover on the passenger side or do I have to remove the whole lower front end of the motor?

THX,
JB
 
I would remove the fan belt ( yes it can be a pain to remove) and start the engine, I had a noise that was hard to locate, the stamped riveted steel generator pulley was coming apart. One other thing to check is for oil flow, remove the plug inline between the distributor and oil pump on the side of the engine block. Or remove the lower connection of the oil return tube, you should have oil flowing in a few seconds .
 
John, to answer your question as to why a knock would happen after sitting in storage.

It wouldn't happen due to storage. The noise probably started 10 years ago but was not noticed.

Did you change the oil before it was started?

Did your pour some oil into the spark plug holes before the first start?
 
I did a oil change right before storage, check the oil and then started it I did not put oil down the holes before cranking it over.
 
Short out the spark plugs one by one and see if the knock goes away. A log screwdriver works well for this. No need to remove any parts and its a quick test that will rule out your rod bearings as the source of the noise.
 
If you remove timing gear side cover, there’s a pan bolt that threads into cover base. Easy to forget and wonder why it won’t come off. Been there done that.
 

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Call some of the guys from your local Model-A chapter to come over and give a listen, maybe help diagnose. Club members are always willing to pitch in.

In ten years I am sure you are a local chapter member, right?

You can put your state/territory on your profile.
 
Okay, status update. Took the timing side cover off looked great. Pulled the pan off, everything looked great. Plastiguaged the mains came up with between .0018 and.0020 on all of them (babbit), everything looked great.
Before that I did short the plugs one at a time and no change in noise.

Thanks for all the great suggestions, I am stumped.

-JB
 
Push the timing pin against the gear, if the noise changes or quiets down the gear may be loose, either a loose nut or the gear separating from the hub.
 
unsichtbarre said:
Okay, status update. Took the timing side cover off looked great. Pulled the pan off, everything looked great. Plastiguaged the mains came up with between .0018 and.0020 on all of them (babbit), everything looked great.
Before that I did short the plugs one at a time and no change in noise.

Thanks for all the great suggestions, I am stumped.

-JB
Click to expand...

When you had the pan off did you check the clearances on the rod bearings too?
 
Sources of knocks: The bearings, the cam moving in and out, a loose cam gear, problems with the generator or water pump, sometimes an exhaust leak can sound like a knock, bent rod causing it to move back and forth on the piston pin, preignition, ignition too advanced, valves sticking, ring gear not up against flange on flywheel. I am sure there are others.

Because you were trying to start the car for a while without success, look to see if the ring gear has slipped on the flywheel.
 
THX, I am now feeling like the knock is further back on the clutch or flywheel. I had run the engine without the belt to eliminate accessory problems. Definitely not an exhaust leak. I have confirmed valve operation by watching them. I have looked in cylinders with a scope, looked fine.
I am going to look further at the timing gear, but I am kinda thinking clutch/flywheel related. I have tried with and without clutch depressed and result is same, confirmed clutch is releasing. I also noticed I can't get the fan belt off completely. Does not clear a hump/bolt right below the main pully. I guess that would mean the motor mounts are worn?

THX,
-JB
 
JB, Take the starter out and look at the ring gear while having an assistant turn the engine over with the hand crank. If it is off the flange you should be able to move it back into position.
 
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