351 W Problem - Diagnosis Needed

[jim_howard_pdx]

Hi

We ran our 351 Windsor last night at the drags. After 3 decent passes with the engine performing I ran the car a 4th time. It ran well, I began slowing down to make the turn off the drag stip. When I slowed to around 30 mph I noticed something that sounded like a rod knocking sound.

When I reached the pit area, I noticed the engine was running a little rough. It seemed to be running hot, and dieseling a bit so I pulled the ignition from 7 degrees to 2 degrees which did smooth it out.

Then I checked the oil, and added a quart. I noticed a small, miniscule bit of metal debris on my oil towel, so I pulled the dip stick about 6 times and found a couple more of these tiny bits of metal. I am not sure if it is aluminum or steel. The debris is very small and bright in appearance.

The oil pressure was acceptable both during slow down and on the drive back to the pit area.

We drove the car home, running the lightest load possible. It exhibited the rod knock sound louder at 45 mph and less loudly at 55. However there was also a different sound that could be rod or oil pump related.

This morning I plan to pull the oil pan off and inspect the bottom end. Is it possible to see signs of a spun rod bearing without removing the rod caps?

Has anyone ever experienced an oil pump failure? I believe my unit is a mellings high volume unit.

Should I pull a main bearing cap and inspect the main bearing condition? With tiny metal shards running through an engine at 6,000 RPM I might expect some bearing damage.

Any other thoughts?

[HotRoddin]

I'd stick a magnent on it and find out if its iron or aluminum ... and if your gonna pull the pan, then by all means check the bearings and the crank journals ... its to easy to do once you have the bottom end exposed not to go ahead and do it.

The only way i know to tell if you've spun a bearing without taking it apart is if it spun it so badly that the heat has turned the rod caps blue ... but once you have it exposed, just take it off and see for yourself.

You said your oil pressure seemed to be ok so why do you suspect an oil pump failure ?

If those particles turn out to be aluminum, especially with the dieseling i'd be looking hard at the pistons. Do a compression check, you might be able to narrow that down a bit ?

Hope there might be a tiny bit of help in all that ? lol

[jim_howard_pdx]

When we drove home we heard both the rod knock and a sound like something spinning against something stationary. I was not sure if the oil pump was affected one way or the other.

We found that rod 6 was lose and rattled about freely. This explains the rod knock. Now we plan to pull the engine, source a good refurbished crank, and head to a balance shop to get a replacement rod balanced and get the new crankshaft set up for the block.

My wife thinks it is time to find a new hobby. I love this Mustang, and I love the power and torque of this 351. I guess I will get this fixed and think about building a purpose built race car for the future. I guess my desire for a convertible project car can wait a bit......

[jim_howard_pdx]

All 8 forged TRW pistons were in great shape. Combustion chambers look fine.

4 of the 8 top rings were fractured in half. Second rings were all fine.

Front rod bearings were excellent. The 2 rod bearing was solid copper, and number 6 was spun with only the steel backing support present. The 3-7 and 4-8 rod bearings were solidly copper as well.

All the main bearings were solidly copper. Since everything originally bolted up so well, and spun so effortlessly, I was certain that the bearings would hold up better. Guess 375-400 HP is a high load on those bearings.

Any suggestions on what I should do for replacement bearings would be appreciated.

[87lx58]

You need to resize all 8 rods. Rods become out of round with spun bearings and lots of use. Never install new rods bolts without resizing the rods. Make sure the rod chamfer always faces the outside when installed on crank. Standard clevite or FM bearings are fine for the rods. Your rings are broken from uncareful installation or ends butting.