Engine Knock at 2000 RPM
 

I had my 1930 model A engine rebuilt about 1200 miles ago. It was rebored, babbitt removed and shell bearings installed. I could hear a light knock from the beginning. The engine re-builder claimed all was normal.

Last winter, he agree to re-inspect the engine if I removed it from the frame. He dismantled it and while he had it apart, I had a Synders touring camshaft install and a Snyders 6:1 high compression head installed. The re-builder claimed he could find nothing out of order with his rebuild.

The engine seems to sound normal at low RPM but rattles as 2000 RPM is reached.

Read a couple threads talking about pistons hitting the head or the head gasket if it protrudes into the bore.

Any other ideas? Any way to check pistons hotting head or gasket without removing the head.

Re: Engine Knock at 2000 RPM
 

Are you positive it is an internal engine noise and not transmitting peripherally?

Re: Engine Knock at 2000 RPM
 

Odd, I had my engine rebuilt with inserts and it is making a similar noise! I have H/C head and electronic ignition. Builder claims too much advance. I've changed distributor back to points but knock still there. I've given up! Just drive it, and when it breaks, then I'll know what to fix!

Re: Engine Knock at 2000 RPM
 

I have a Snyders 6.1 head, babbits and drive at 2,300 rpms and no noise.

Re: Engine Knock at 2000 RPM
 

Pull the plugs and look at the top of the pistons with a bore scope. If they are touching there should be a mark left on the piston.

Re: Engine Knock at 2000 RPM
 

So - - - is it a knock, or a rattle? Or did it evolve?

Re: Engine Knock at 2000 RPM
 

It is knock that was there from day one of the overhaul (but fairly quiet). The knock seems to be getting louder at 2000 rpm and above.

Analysis of the oil shows high copper, iron, lead, and tin.

Re: Engine Knock at 2000 RPM
 

Copper typically indicates a bearing, likely a main in this case. If it was a throw it would have "thrown" by now. A main can knock for quite awhile, maybe not as long on a 3 main model A as a modern engine but a lot longer than a rod. I would pull the pan and check all of them starting with the mains. Does the knock change with the throttle, IE better or worse when you give it gas or when you let off the gas?.

Re: Engine Knock at 2000 RPM
 

Knock is only under load and 2000 rpm +. Can not hear knock sitting still and revving the engine with no load. Noise is there in all gears at 2000+.

Re: Engine Knock at 2000 RPM
 

Aluminum timing gear can make a metallic rattle although I think it most likely starts at lower rpm. Is a motor mount loose or front pulley touching? Take a prybar to lift engine while running.

Re: Engine Knock at 2000 RPM
 

Hard to hold on to that crowbar while putting on a load at 2000rpm going uphill

Re: Engine Knock at 2000 RPM
 

The only way you get a copper reading on a model a is an engine with insert bearings and one or more of the bearings is coming apart

Re: Engine Knock at 2000 RPM
 

thats why I like high speed babbit..no thin liner of babbit ...nope,its all babbit..

Re: Engine Knock at 2000 RPM
 

Will the noise change if you retard the spark ?

Re: Engine Knock at 2000 RPM
 

I will double check that today, but pretty sure I have done that with no change---will let you know.

Re: Engine Knock at 2000 RPM
 

If I am reading the #1 post correctly, the knock has been in the engine since it was first rebuilt. Then upon a disassembly and inspection, a high compression head was installed. Since the knock has been there since the rebuilt engine was first completed, I think I would rule out piston interference.

As for the high copper, lead, and tin, ...these are items found in bronze, -and if the thrust bearing on the main was made from Bronze and then clearanced too tightly, this could be the source of those high levels in the oil.

Without being able to check clearances with micrometers and indicators, anything we say will just be speculation. Maybe it is one or more bent connecting rods, maybe tappet to bore clearances are excessive, maybe the line-boring operation bedded the crankshaft outside of being truly parallel with the cylinder case or even straight in the centerline.

Re: Engine Knock at 2000 RPM
 

Trace values of a substance,like the copper component of bronze wont register as a 'hard value' on the spectrometer. Generally a copper 'warning' is from the bearing shell once the babbit is gone.Bronze wear will show as bronze.
Oil samples require rigorous attention to sample collection method as well as a baseline of samples to compare to.

Re: Engine Knock at 2000 RPM
 

Sorry to hear this has happened to you. Did the engine rebuilder ever hear this rattle at 2000 rpm? If no, why not? If yes, what did he say?

Re: Engine Knock at 2000 RPM