The Ford Barn

pawillie · 06-13-2025, 06:08 PM

Need to hear from someone with a little more brain than I have. What am I missing? I replaced the crank gear with a new timing gear, meshed nice and tight. readjusted the all the main and rod bearings, removing shims in each till engine wouldn't turn and then replaced on shim. Car starts at turn of key, idols good but when accelerating makes a knocking noise. When letting off the throttle it quiets down. Picks back up when pressing throttle. I installed a new oil filter system, could it be starving for oil? Filter gets real hot. Thanks for some help.

Marshall V. Daut · 06-13-2025, 06:17 PM

Could your ignition timing be a bit too advanced? Does the engine knock at idle? If it doesn't knock at idle, retard the timing inside the distributor and see if that helps. Also, short out each spark plug to see if the noise goes away or gets worse. My engine had a double knock at idle when the plug in #1 cylinder was shorted = wrist pin. 'Turns out the upper rod bore was egg-shaped and the bushing was loose, causing the double knock.
Marshall

pawillie · 06-13-2025, 07:38 PM

Don't hear it at idol and I have upgraded to an auto advance unit. Gets louder when accelerating engine. Quiets down when letting off gas pedal.

Big hammer · 06-13-2025, 08:10 PM

Upgraded auto advance unit is advancing your timing way too much causing pre destination ! Stop driving it until you get the full advanced timing reduced period ! What’s nice about the hand timing lever is you can manually retard the timing on the fly

Ruth · 06-13-2025, 08:20 PM

If you have the Nu-Rex auto advance and you still have the spark lever connected, retard the timing (push lever up). This should stop your pre-ignition.

The Nu-Rex will advance your ignition 30°. That's is to much IMO. I limit mine to ~27° total.

nkaminar · 06-14-2025, 05:46 AM

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Remove any automatic advance. Find the knee in the ignition curve. Use a degree wheel to determine what advance that is. Re install the automatic advance. Use the degree wheel to set the maximum advance to the advance you found at the knee.

Too much advance will destroy your rod bearings in short order.

To find the knee, retard the ignition then set the hand throttle to a fast idle, about 1,000 to 1,200 rpm. Then advance the ignition one click at a time until one more click will not make the engine run faster. Retard one click and that is the knee where your ignition should be running.

pawillie · 06-14-2025, 08:39 AM

Don't you have to pull lever down to retard instead of all the way up? Also, hate to think of getting rid of the Nu-Rex as since installed the car starts every time, on time by simply lifting choke and letting go. I'm sort of a newcomer with this so can you help me with recognizing difference between pre-ignition and bearing noise? Thanks

ronn · 06-14-2025, 08:48 AM

no retard is up!

Y-Blockhead · 06-14-2025, 08:50 AM

Quote:

Originally Posted by pawillie

Don't you have to pull lever down to retard instead of all the way up? Also, hate to think of getting rid of the Nu-Rex as since installed the car starts every time, on time by simply lifting choke and letting go. I'm sort of a newcomer with this so can you help me with recognizing difference between pre-ignition and bearing noise? Thanks

No, Retard is all the way up... you should not have to deal with the lever with the Nu-Rex auto advancer if you initial timing is correct. As said, the Nu-Rex advances the timing 30°.

old31 · 06-14-2025, 09:37 AM

After you install the nurex, push the left lever all the way up, and leave it there. Never touch it again.

pawillie · 06-14-2025, 11:16 AM

Thanks much, that is where I have it positioned. Perhaps I need to tighten the bearings some more. I still can turn engine over fairly easy. Should there be a slight drag? Don't want to over tighten, for sure.

nkaminar · 06-14-2025, 02:12 PM

If the shims you took out to adjust the bearings are the standard type they peal off 0.001 inch at a time. If the engine was tight and you put one of these shims back on one side you now have 0.0005 clearance. The bearings should not knock with that clearance. Even if you put a shim back on both sides it should still not knock. If you do the bearings again, measure the shim thicknesses with a micrometer or dial indicator.

It is very important that you verify the timing advance. There was a good article in one of the recent magazines on how to do that. You will need a degree wheel and pointer and a stobe light. 30 degree advance may be too much for even a stock head and is for sure too much for a high compression head.

Here is what I would do: Re time the engine with the distributor cam moved more retarded by 10 degrees. That will be 20 degrees at the crankshaft. Then use the ignition advance lever to find the knee. Lock the ignition lever at that position. If the car still knocks then you have loose bearings.

1crosscut · 06-14-2025, 03:38 PM

You replaced the timing gear, added an oil filtering system, switched to an automatic timing advance system and adjusted the bearing clearances.

Was the engine knocking before doing these things?

Dino's A · 06-14-2025, 04:26 PM

I just don't understand why so many Model A's have this added or something else added on? Mine is stock and always starts up so fast and drives great. Seems like most of these additions always lead to trouble eventually.

pawillie · 06-15-2025, 07:35 PM

I replaced the crank and timing gear as they kind of chewed on each other's teeth. And unfortunately, it was knocking before the adjustments and additions. Since car starts and runs good, I will digest the various suggestions above and if no luck will readjust bearings.

Chuck Sea/Tac · 06-16-2025, 04:09 PM

Two other sources of a knock
1) center cam bearing(the block) is worn out allowing cam to move up and down producing a knock.
2) this happened to me, not sure how common it is? The cam thrust on the gear end of the cam is worn out and the cam bounces forwards and backwards from a weak cam spring. The rear end of cam knocks on the fly housing.

grudicil · 06-20-2025, 05:16 PM

I had a similar noise years ago. Adjusting the main and rod bearings didn't help, and I even tried a new cam gear and thruster since the knock was closer to the front of the engine. Turns out the #2 rod babbitt had failed and cracked. The rod cap's babbitt was fine, and that fooled me initially.

06-13-2025, 07:38 PM	#3
pawillie Member Join Date: May 2016 Posts: 41	Re: Engine noise Don't hear it at idol and I have upgraded to an auto advance unit. Gets louder when accelerating engine. Quiets down when letting off gas pedal.

06-13-2025, 08:10 PM	#4
Big hammer Senior Member Join Date: Jun 2014 Location: Land of Lincoln Posts: 3,431	Re: Engine noise Upgraded auto advance unit is advancing your timing way too much causing pre destination ! Stop driving it until you get the full advanced timing reduced period ! What’s nice about the hand timing lever is you can manually retard the timing on the fly __________________ Don't force it with a little hammer tap, tap, tap get a bigger hammer tap done

06-13-2025, 08:20 PM	#5
Ruth Senior Member Join Date: May 2016 Location: Glide, Oregon Posts: 1,441	Re: Engine noise If you have the Nu-Rex auto advance and you still have the spark lever connected, retard the timing (push lever up). This should stop your pre-ignition. The Nu-Rex will advance your ignition 30°. That's is to much IMO. I limit mine to ~27° total. __________________ Ruth "Sometimes you really DO need to read the whole thread"

06-14-2025, 05:46 AM	#6
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 5,867	Re: Engine noise Sponsored Links (Register now to hide all advertisements) Remove any automatic advance. Find the knee in the ignition curve. Use a degree wheel to determine what advance that is. Re install the automatic advance. Use the degree wheel to set the maximum advance to the advance you found at the knee. Too much advance will destroy your rod bearings in short order. To find the knee, retard the ignition then set the hand throttle to a fast idle, about 1,000 to 1,200 rpm. Then advance the ignition one click at a time until one more click will not make the engine run faster. Retard one click and that is the knee where your ignition should be running. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

06-14-2025, 08:39 AM	#7
pawillie Member Join Date: May 2016 Posts: 41	Re: Engine noise Don't you have to pull lever down to retard instead of all the way up? Also, hate to think of getting rid of the Nu-Rex as since installed the car starts every time, on time by simply lifting choke and letting go. I'm sort of a newcomer with this so can you help me with recognizing difference between pre-ignition and bearing noise? Thanks

06-13-2025, 06:08 PM	#1
pawillie Member Join Date: May 2016 Posts: 41	Engine noise Need to hear from someone with a little more brain than I have. What am I missing? I replaced the crank gear with a new timing gear, meshed nice and tight. readjusted the all the main and rod bearings, removing shims in each till engine wouldn't turn and then replaced on shim. Car starts at turn of key, idols good but when accelerating makes a knocking noise. When letting off the throttle it quiets down. Picks back up when pressing throttle. I installed a new oil filter system, could it be starving for oil? Filter gets real hot. Thanks for some help.

06-13-2025, 06:17 PM	#2
Marshall V. Daut Senior Member Join Date: Apr 2011 Location: Davenport, Iowa Posts: 2,627	Re: Engine noise Could your ignition timing be a bit too advanced? Does the engine knock at idle? If it doesn't knock at idle, retard the timing inside the distributor and see if that helps. Also, short out each spark plug to see if the noise goes away or gets worse. My engine had a double knock at idle when the plug in #1 cylinder was shorted = wrist pin. 'Turns out the upper rod bore was egg-shaped and the bushing was loose, causing the double knock. Marshall

06-14-2025, 08:48 AM	#8
ronn Senior Member Join Date: Feb 2011 Location: NNNNNNNNJJJJJJJJJJ Posts: 7,650	Re: Engine noise no retard is up!

06-14-2025, 09:37 AM	#10
old31 Senior Member Join Date: Jan 2016 Posts: 2,460	Re: Engine noise After you install the nurex, push the left lever all the way up, and leave it there. Never touch it again.

06-14-2025, 11:16 AM	#11
pawillie Member Join Date: May 2016 Posts: 41	Re: Engine noise Thanks much, that is where I have it positioned. Perhaps I need to tighten the bearings some more. I still can turn engine over fairly easy. Should there be a slight drag? Don't want to over tighten, for sure.

06-14-2025, 02:12 PM	#12
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 5,867	Re: Engine noise If the shims you took out to adjust the bearings are the standard type they peal off 0.001 inch at a time. If the engine was tight and you put one of these shims back on one side you now have 0.0005 clearance. The bearings should not knock with that clearance. Even if you put a shim back on both sides it should still not knock. If you do the bearings again, measure the shim thicknesses with a micrometer or dial indicator. It is very important that you verify the timing advance. There was a good article in one of the recent magazines on how to do that. You will need a degree wheel and pointer and a stobe light. 30 degree advance may be too much for even a stock head and is for sure too much for a high compression head. Here is what I would do: Re time the engine with the distributor cam moved more retarded by 10 degrees. That will be 20 degrees at the crankshaft. Then use the ignition advance lever to find the knee. Lock the ignition lever at that position. If the car still knocks then you have loose bearings. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 06-14-2025 at 02:18 PM.

06-14-2025, 03:38 PM	#13
1crosscut Senior Member Join Date: Feb 2011 Location: Lincoln, Nebraska Posts: 2,011	Re: Engine noise You replaced the timing gear, added an oil filtering system, switched to an automatic timing advance system and adjusted the bearing clearances. Was the engine knocking before doing these things? __________________ Dave / Lincoln Nebraska

06-14-2025, 04:26 PM	#14
Dino's A Senior Member Join Date: Jun 2016 Location: Arcadia, Ca. Posts: 309	Re: Engine noise I just don't understand why so many Model A's have this added or something else added on? Mine is stock and always starts up so fast and drives great. Seems like most of these additions always lead to trouble eventually. __________________ 1928 Roadster Pickup 1930 Tudor 1943 Ford WWII Jeep 1968 Taco Minibike Member, Santa Anita Model A's Arcadia Ca.

06-15-2025, 07:35 PM	#15
pawillie Member Join Date: May 2016 Posts: 41	Re: Engine noise I replaced the crank and timing gear as they kind of chewed on each other's teeth. And unfortunately, it was knocking before the adjustments and additions. Since car starts and runs good, I will digest the various suggestions above and if no luck will readjust bearings.

06-16-2025, 04:09 PM	#16
Chuck Sea/Tac Senior Member Join Date: May 2010 Location: Between Seattle & Tacoma Posts: 2,411	Re: Engine noise Two other sources of a knock 1) center cam bearing(the block) is worn out allowing cam to move up and down producing a knock. 2) this happened to me, not sure how common it is? The cam thrust on the gear end of the cam is worn out and the cam bounces forwards and backwards from a weak cam spring. The rear end of cam knocks on the fly housing.

06-20-2025, 05:16 PM	#17
grudicil Junior Member Join Date: Jul 2010 Posts: 17	Re: Engine noise I had a similar noise years ago. Adjusting the main and rod bearings didn't help, and I even tried a new cam gear and thruster since the knock was closer to the front of the engine. Turns out the #2 rod babbitt had failed and cracked. The rod cap's babbitt was fine, and that fooled me initially.