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.

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

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.

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

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.

Re: Engine noise
 

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.

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

Re: Engine noise
 

no retard is up!

Re: Engine noise
 

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°.

Re: Engine noise
 

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

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.

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.

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?

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.

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.

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.

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.