Im looking into renewing main and rod bearings in my '87 351W. Is it possible to complete the work w/o removing the eninge?

Thank You

 

No.. and that is besides the fact that it would be pointless to do so.

 

Ok, you say its not possible. If itis possible why would it be pointless? Anyone else ever here of renewing the bearings with the engine still installed in the truck?

 

IF the crank has been checked and is in good shape you can roll a set of main bearings in it. IF the rods have been checked and are in good shape you can put a set of rod bearings in it. But if it needs mains and rod bearings chances are prolly close to 100% the crank needs grinding. If you are selling it and dont mind screwing someone, go ahead. If you plan on keeping it go ahead and rebuild it.

 

Why do think it needs new bearings? Low oil pressure or knocking?

 

The not possible is very likely the oil pan removal, I don't know if 2wd's are different but on my 94 F150 4x4 351 I don't think the oil pan could be removed with the engine in the truck and I doubt the older trucks are much different.
The pointless is debatable depending on the engine condition, on a gas engine generally if that mains/connecting rod bearings are shot the rest of the engine is pretty tired as well but know of a few guys that have done just that and have gotten many more years of use out of their truck.... But if you have to pull the engine to remove the oil pan you might as well do a full rebuild.

 

And there is the catch.. you can't know what the engine condition is without removing and inspecting the various components. Crank bearing surfaces don't often go out of shape but the big end of the connecting rods do go slightly egg shaped over time and this wears the bearings unevenly. Installing new bearing on these rods without grinding the openings circular causes pinch points that will quickly lead to a bearing failure. Sure you might get lucky and keep the motor running but there is an equal chance you may not and and then you will have trashed the motor beyond repair.

But besides all that, the motor has to be raised up quite a bit just top get the oil pan off so you are disconnecting the exhaust and mounts anyway and then you got to work in tight quarters under the truck. But you are now 1/2 way to completely removing the motor so why not just jerk it all the way out and either rebuild it correctly or swap in a lower milage used motor.

 

You can get a good idea of the piston ring and valve health from a compression test, The camshaft and lifters are only a guessing game. An explanation of why you're wanting to do this and a better description of the truck/problem would help us with the correct repair?

 

That's interesting I've never heard of seen of that...?

 

Thanks for all the replies. Im looking into renewing the bearings to correct low oil pressure when the engine is up to temp. No knocks or unusual noises, truck runs great, just looking to bring the pressure up a bit. Right now Im running 15-40 with a can of Lucas Oil Additive. At cold start up the pressure it at 40psi, when warm its at about 14psi at idle. Idle RPMs are at about 1000. I wanted to renew the bearings the easiest way possible, but it sounds like there is not short-cuts to do this. thanks again for the replies

 

14 at warm idle is on the low end of acceptable. What does it run at cruise rpm? Can you get 10 psi per 1000 rpm?

 

At 55MPH/about 2700RPM I read about 35PSI when its up to temp.

 

Just run it. Look for another 351w and do a rebuild/upgrade etc. Do it on your own schedule and just swap out the whole thing once you're ready. Serving suggestion. ymmv

 

To be perfectly honest if the truck isn't burning oil like crazy and oil pressure is low I wouldn't have a problem with putting new crank and main bearings in an old engine, it's never going to be as good as a full rebuild but you will have an old engine with good oil pressure. I've only rebuilt lawn mower and Diesel tractor engines and as long as they weren't knocking from bearing wear have never had a problem with crankshaft's or connecting rod's being out of round, if you can figure out how to lift the engine enough to remove the oil pan it could possibly be a good way to get some more life out of motor.
I just recently tore apart the 2.9 that I swapped out of my 89 Ranger mostly for antifreeze in the oil but also very low oil pressure and really think if I had put new bearings in the motor it would've fixed the oil pressure problems. The cam bearings that are supposed to be the problem look like new but the connecting rod in main bearings were very worn, it wouldn't have fixed the 3 quarts of oil every 3000 miles but a free low mile engine and transmission with a 120$ complete seal/gasket kit was a very lucky upgrade.

2.9 Connecting rod bearing.

You can't see it but there is an impressive amount of wear on the cylinder walls, around 220,000 miles on the 2.9.

 

85E, thanks for your advice. I may just run it for now and look to pull it in the future (the oil pressure doesent seam to be as much of a concern as I thought). I just put an actual pressure gauge in over the weekend and when I saw what the PSI was when the engine was warm, I got concerned. TWIGS, I hope Im not where close to that much bearing ware. I have close to 0 oil loss every 3000 miles.