So I've got the 351w out of my '95 F-150 to fix some leaks and freshen it up a little bit. Due to some difficulty extracting a broken exhaust manifold stud, it is getting a rebuilt set of GT-40 heads. Oil pan is rusted so that is getting replaced, and I figured I'd do the oil pump while I was in there. The truck has 155k miles on it. Quite a few people have mentioned popping one of the main caps off to check bearing wear. Others have suggested that I go ahead and replace them no matter what they look like.

What do y'all think? Just check one main? Check them all? What about rod bearings? I'm sure it will show wear, but how much is excessive? Some folks say not replacing bearings without polishing the crank, but I've also been told not to worry about it and just "roll" the new bearings in. What say you?

 

Unless you have reason to suspect bearings are out of tolerance (not just based on miles) I would leave them alone.

If you do check them and end up replacing them (necessarily or preemptively), you need to measure things and make sure they're still round. Polishing the crank will depend on the condition of the journals. You might need machine work.

Sometimes people get lucky just rolling in new bearings. Sometimes they don't.

My two cents: one of the most valuable lessons I've learned over the years is don't fix what isn't broken.

 

This here.

Unless you know that it had an issue leave it alone. My truck has coming up on 300k miles and pulls decent pressure with 10w30. If you replace the pump maybe go high pressure but no need for high volume

Since you are pulling the heads for a repair, I would maybe check quench distance and if it's off too much I would try to get it between. 040 and .044. But, that's about as far as I would go.

 

I think it comes down to personality-

personally, I can't leave well enough alone. If I've gone all the way to getting the engine out and the pan off.
I'm going to pop the caps. On every journal. And most likely change all the bearings. I'll re- ring it too, while
I'm there, because.... well,. it's apart. And the parts are pennies compared to how much I value the little bit of time
I get to work on stuff like that.

I guess if I care enough about the vehicle to pull the engine, I figure I'm going to keep it for a while, and knowing
everything's OK in there is important to me.

I tend to draw the line at boring- if the heads come off and the cylinders are
measurably tapered, that's where I have to decide if I'm just slapping it back together as- is, running it for a bit more
and getting something else, or doing a full rebuild, and all that THAT entails (stroker, overbore, etc, etc. etc.)
Often, if I like the truck, I'll toss it back together, and then start building another engine for it as I have time and funds.
That's kind of where I am with the 351 in the 'new' 250- it's 'ok', but eventually, I'd like something more exciting.
So I'm looking for a roller block, GT40 heads, blah- de- blah to do a 'junkyard hotrod' motor for it.

t
would check the bearings.
And let the cat out of the bag.

 

My original plan was to just leave the bottom end alone because I wasn't aware of any issues, and it should last quite a few more miles. Thanks for the input.

I will take some measurements when I get a chance. I got the Fel Pro 9333 head gasket because that's what all the mustang guys seem to use, but it appears to have a .047" compressed thickness.

Thanks for the input. I'm with you in that I know that if I tear into it I'm going to want to go all the way with it - machine shop, new rings, bearings, maybe 393 stroker kit, etc. I actually started a thread about EFI strokers the other week, but that's going to require a new tune and more money. I think I will save that for down the road. On a project that's already over budget, if it's not necessary, I'd like to avoid it.

 

Yes bearings are one of those things that are better left alone, if the motor makes good oil pressure it doesn't need new bearings, if it doesn't make good oil pressure it needs a full rebuild and anything less is just a waste of time and money.

 

Yeah, need to get a measurement on the relationship of the piston crown to the deck surface. While it should be zero deck, better safe than sorry. If it's off a bit, it's a good Idea to tighten it up a bit. Once, you get above .050 your chance for preignition goes up and efficiency starts going down.

 

Thanks. By the way, I've used the search function quite a bit during this project, and several of your old posts have been a lot of help to me.

So I don't have a dial indicator or the proper jig to really check, but I did my best with a straight edge and some feeler gauges. I checked a cylinder on each bank. Both seemed to be exactly the same. I'm gonna try to explain this the best I can - On the uphill side of the piston (toward the valley), I could not get the .0015" (the thinnest size I had) in between the straight edge and piston so I assume it's pretty close to zero. However, on the downhill side (toward the outside of the block), I could barely slide the .0015" between the straight edge and piston. .002" would not go.

So I guess that puts the piston to deck clearance at zero to .0015" below. So you've got me rethinking my head gasket choice.

 

That's pretty close to zero. You can get away with the gasket you were talking about. I doubt you will have any issues.

I like to close my quench as much as possible personally. I haven't built an engine in the last 20 years with a quench distance over .040 and even at 10:1 I've gotten away with 87 octane for just cruising and if the engine is going to be worked hard and timing is on the ragged edge 91 always does the job with no ping.