The following is a bit lengthy, but my goal is to get some input from the experts, and also document this issue if it happens to anyone else. And hopefully, prevent any boneheaded mistakes that I made!

My 400 has been an extremely slow project that started about 2 years ago. I "finished" the truck (1973 f-250 4x4, NP435) a couple months ago, drove it to paint, and to get the emissions tested, probably about 20 miles total on the truck. Startup and break in went as expected, but on the two longer trips when the truck was up to temperature, the oil pressure didn't register on the factory gauge, and the lifters were rattleing, apparently from both sides. When draining oil, it looked silver. I assumed it was the camshaft. Regardless, I figured something major is wrong, and I pulled the motor to see what was up. It has been too long to remember if I even used plastigauge to check the bearing clearances.

A little background... I started with a "recently rebuilt" 351M. Added a 400 crank, TMI pistons, 255 comp cams cam, stock heads, new rod and main bearings, and had the assembly balanced. I did not replace the cam bearings, somewhere along the line through the restoration, water got in the motor. I believe it was through a poorly sealed turkey pan gasket, but the motor was never run with water, just primed.

So, I got the motor out today, and tore apart the top end. I started pulling out the lifters, expecting to see a dished lifter, to my surprise, it had a couple little scratches, but not really not a problem. However, the sides of the lifter showed a little wear. All 16 of the lifters came out a little easier that normal, so I suspect that the lifter bores might be a little out of spec. The camshaft was removed, and it looks good. Basically, everything looks like a little bit of grit might have been circulated in the oil...

So the questions for now are, without a fancy bore indicator, how do I tell if the lifter bores are bleeding off to much pressure... or is that even a possibility? Is there a chance that the Cam is damaged, is there a way to visually tell if I should replace it.

I also have never seen a dissasembled engine with only 20 or so miles. The sides of the cylinders where the pistons thrust are already very smooth, where the fronts and backs still have the hone. Is this to be expected?

Thanks for any input... The shortblock teardown starts tomorrow, findings will be posted!!

 

What do the main & rod bearings look like ?

 

Most cylinder wear does occur in line with the rotation of the piston/connecting rod, and very little on the walls front and back of each cylinder. However, I would expect crosshatching still evident with very little miles on the engine, but like you, never saw an engine opened up so soon...

I would plastigauge those bearings. Your oil pressure being low is what is causing the noisy lifters, not the other way around.
How easy does the camshaft turn when in place? The cam bearings are very soft and should fit the cam unless worn beyond use.
It would be worth the time to check out the bottom end. I would pull each cap and measure bearing clearance, and retorque everything for peace of mind. (don't forget thrust bearing procedure)

 

OK, here is the lesson, dont be lazy and assume the bearing clearances are OK. after 20 miles, the bearings look like they have 200k miles... Destroyed The crank also needs to be returned.

Using plastigauge, I got .002ish on the rods, and over .006 (red plastigauge doesn't register) on the mains. Using calipers, I got front to back on the mains as a minimum...

1. 2.970
2. 2.973
3. 2.965
4. 2.970
5. 2.980

the rods (as a pair, front to back) are at
1. 2.288
2. 2.288
3. 2.288
4. 2.280

on main #1, there is a portion of the journal that didn't get worn, it is at 2.980, which would indicate .020 under. all the clevite bearings were .020 under also.

Hopefully this crank mains will clean out at .040 under! New bearings, and clearances checked prior to starting it again!!

 

hi, just wondering what oil your where using , maybe a slightley heavier oil might solve your problems