351W problems... Problem solved!

Guys,

Need some help here.

351W.  Basic stock rebuild.  Fired up and showed good oil pressure on gauge but rolled the cam bearings in their journals and showed lack of oil on the main and rod bearings...

Give me some things to check.  Engine is out and apart right now.  Just looking to make sure this doesn't happen again when I reassemble it....

Thanks in advance

Check pick up screen and oil holes in crank journals along with the oil pump look at the plate that bolts on the pump if it has scarring it probably is no good... hope some of this helps

Over the high limit dimension on the cam journals or being tapered as well.

I don't know about your 351W but, cams come that way for a 385 and some other engines, all the time. Polishing, sanding or even grinding main journals if they are over a thou to big is required in a lot of cases

With older worn-in cam bearings this does not seem to show itself.

Did you assemble the engine using grease?  If so that can certainly cause these sort of problems. I saw this very problem on a 351 Windsor that someone put together using white grease and the engine spun the cam bearings due to lack of lubrication(grease plugged the holes).

Randy - Are you saying that the cam may have been a few thou large on the diameter? Could it be that way yet still spin freely in the journals when installed?

Dave - No, it was assembled by a local shop. But my dad and I changed the cam after it was built, but before it was fired. We used the Comp Cams cam lube with it.



Any oil gallery plugs that could be missing? The engine is at the shop and I plan to pick it up and look at it myself in a few days. It had good pressure while priming it with a drill and even had good oil flow to the rockers during priming. We're all scratching our head on this one... Only other thing I can think of is the oil pan to pickup clearance got out of whack during engine installation. Oil pan got smacked or something.

Not that the cam was oversized, the bearings themselves a little on the oversized side. Once things got warm, not enough clearance for cam and oil in bearing. As for main and rod bearing scratching... oil pickup clearance in pan. Oil pick-up to pump allowing air??? Oil pump to block mating not flush... other things, typical, block not cleaned properly before assembly and trash pumped through bearings. If there is crap left in passages after the oil filter, the only place it can go is through the bearings.

How is the oil passed through the block? Where's it go after the pump? Does the cam or mains get oil first?

351w oil system diagram

i have had 2 problems with the 351 oiling system.

with a remote oil filter the lines can be mixed up

a sticky relief valve in the oil pump

jbozzelle wrote:Randy - Are you saying that the cam may have been a few thou large on the diameter?  Could it be that way yet still spin freely in the journals when installed?

Dave - No, it was assembled by a local shop.  But my dad and I changed the cam after it was built, but before it was fired.  We used the Comp Cams cam lube with it.



Any oil gallery plugs that could be missing?  The engine is at the shop and I plan to pick it up and look at it myself in a few days.  It had good pressure while priming it with a drill and even had good oil flow to the rockers during priming.  We're all scratching our head on this one...   Only other thing I can think of is the oil pan to pickup clearance got out of whack during engine installation.  Oil pan got smacked or something.

Right but what lube was used when the lower end was put together. In the Windsor engine in my example grease was used in the main bearings where it blocked the oil to the cam bearings.

jbozzelle wrote:How is the oil passed through the block?  Where's it go after the pump?  Does the cam or mains get oil first?

actually ... the front cam bearing is the first to get oil, then the rest of the engine.

Thanks guys. Hoping to pick it all up from the shop this week. I'll post some good pics in hopes of figuring it all out. The engine is complete and just needs to be reassembled once I figure out why it failed.

Hey Mods - Move this to the new SBF section...


Also, should the cam journals be showing any sign of scuffing of some sort where it "grabbed" the bearing?  The cam journals look perfect!

This thing is going on the stand in a week or so and will get the oil gallery plugs pulled and the block brushes pushed through it... Hopefully I'll find a blockage............

Be sure and brush the main to cam oil holes very good. I had one give me a similar issue, and those had been missed. It's better to do it while the cam bearings are out, but it can still be accomplished with them in, but is harder to do a good job.

jbozzelle wrote:Guys,

Need some help here.

351W.  Basic stock rebuild.  Fired up and showed good oil pressure on gauge but rolled the cam bearings in their journals and showed lack of oil on the main and rod bearings...

Give me some things to check.  Engine is out and apart right now.  Just looking to make sure this doesn't happen again when I reassemble it....

Thanks in advance

Is this a remote oil filter...?
Where is the point of oil pressure taken...?

Are you sure the cam bearing oil holes were correctly aligned by the builder before you swapped cams? They may have been wrong to begin with.

rmcomprandy wrote:

jbozzelle wrote:Guys,

Need some help here.

351W.  Basic stock rebuild.  Fired up and showed good oil pressure on gauge but rolled the cam bearings in their journals and showed lack of oil on the main and rod bearings...

Give me some things to check.  Engine is out and apart right now.  Just looking to make sure this doesn't happen again when I reassemble it....

Thanks in advance

Is this a remote oil filter...?
Where is the point of oil pressure taken...?

stock location filter and pressure taken right above filter...

maverick wrote:Are you sure the cam bearing oil holes were correctly aligned by the builder before you swapped cams?  They may have been wrong to begin with.

No clue... Thinking holes may have been off or partially covered or maybe the feed holes from main saddles were clogged... can't tell anything now since the bearings spun...

Old engines I tear down and put rings and bearings in I take the block to the car wash. You can put the car wash wand in the filter hole and sometimes its amazing what blows out of there.

85bigblockfox wrote:Old engines I tear down and put rings and bearings in I take the block to the car wash. You can put the car wash wand in the filter hole and sometimes its amazing what blows out of there.

Yep, I do the same on the engine stand with a blow gun attachment that also pulls solvent from a jug at the same time...

That's all fine and well, but run a brush through them too. The old oils would get caked up in there real bad, and it can be very hard to clean.

Yes brush each and every hole in block,and clean brush w/cleaning solution after each stroke.

Were the cam journals mic'd before bearing installation? The few thou could have been on the OD

I'm back to the "bearings were put in wrong" idea. Since there's no sign of scuffing in the bores, maybe they didn't spin after all.