I have a "52 239 FH and have gone through the engine replacing all bearings, installed adjustable lifters, etc. all was well. Developed a slight knock. Opened it up, re-tightened all rods, mains, adj valves, pulled pistons, replaced a questionable wrist pin, pulled all valve guides, etc, etc. Still have "knock". I was told that it may be a warped flywheel???
I have not gone into this area yet because the clutch and tranny are working fine.
Before I chase this dog, is it a valid pursuit?
Any thoughts?

 

Is the knock at valve train speed or crank speed? That will help to narrow it down. Use tubing and/or a dowel as a "mechanic's stethoscope" to narrow it down some more.

 

I've never heard of a warped flywheel knocking and how it possibly could, I dunno. Whoever told you that hasn't a single clue.

A warped flywheel will usually have blue heat marks because heat is what causes it to warp.

 

I've heard loose flex plates, strange noises. I've heard fuel pumps make strange noises also. Disconnect accessory belt to get a better sound without pumps, generator and fan generating competing noises. Of course, don't run it too long without the cooling system working.

 

Perhaps the guy that told you that has had experience with a dual mass flywheel. A dual mass flywheel will knock like heck if there is any miss in the engine by picking up the vibration from the engine.
Concentrate on the engine.

 

I have checked the top and bottom for signs of the cause of this rather loud noise. I am now grasping at straws for a solution.
The good news out of all of this is that my 29 year old son, who loves "wrenching" has learned a lot about the ol' flathead while helping his Dad chase this gremlin.
I researched the flywheel idea and got very sketchy "maybe" info. Guess I am just wearing down trying to figure it out.
Thanks for your input.

 

Did you run/drive the engine before the rebuild? Was it making that noise? Does it make this knocking under load, idling, or all the time equally? You can eliminate bearings and rotating assembly if it is not different under load.

I put a new clutch PP in mine and it did not quite clear the BH bosses for the trans bolts. It was a pretty hard hit, sounded terrible, but a lesser hit might sound like a knock. Any chance you can record the sound in a video?

 

The rebuild was done a couple of years ago, very few miles on it since then (less than 100).
The noise seems to be related to crank speed, not lifters or valves. It is the same all the time, just increases with engine speed.
I have not touched the flywheel, clutch as the rebuild, due to limited shop space was done while the block was still in the truck.
I will use a stethescope "again" to try and isolate the noise.
Thanks

 

I think Ray may be on track with the fuel pump diagnosis.

So if the block was in the truck for the rebuild, and the trans was also, did you actually pull the crank, or just replace the bearings with new?

 

Just replaced the bearings.
Also, went to elec fuel pump as I relocated the fuel tank outside of the cab., plugged f/p/rod hole.

 

What did you plug the f.p. bushing with?

 

Just plugged the hole, threaded it from the top and thread locked a machine thread bolt in it as recommended in Frank Oddo's Flathead Builders Handbook.

 

What is your oil pressure (on a known mechanical gauge)?

 

60+ on start up then runs at 30 after warming up.

 

I installed a Full flow oil filter system and a new oil pump.