I have an 88 351 with 124K on it. I pulled it out of the truck to put new main and rod bearings in and to replace all the gaskets. The engine kits all come with new rings. Should I install the new rings even though the engine ran good? If the cylinder is slightly out of round will the new rings seal or will this cause more troubles than its worth. I don't want to spend a ton of money on it getting it machined. If the cylinders are all within specs should I put them in?
Any thoughts or suggestions would be appreciated. Thanks.

 

FIRST: Have you removed the pistons yet? If you have not disturbed them, you can leave them alone. This is not super-easy as you have to do all bearing work VERY CAREFULLY to avoid dinging the crank rod journals with the SIXTEEN rod bolts. Here are some tips:

o Put 16 pieces of any hose that snugly fits on the rod bolds. The pieces of hose should be at least four inches long.

o You can take it apart by yourself, so long as the hoses are keeping all 16 rod bolts from contacting the crank journals. Take off all rod & main caps and then just lift the crank straight up out of the block, which should be upside-down at the time. Remove all the old bearing inserts.

o After wiping all the bearing bores dry, insert the upper halves of all rod & main bearings. Don'f forget assembly lube.

o Get as many helpers as possible to help with the crank reinstall - as many as can stand around the engine - hopefully it is on a stand. Four helpers (two rods each), with you doing the crank are just right. (I have done this with only ONE helper, but it takes a pretty coordinated helper.) Then slowly lower the crank in place in the reverse motion of the removal, with all your helpers moving their rods appropriately.

If you have disturbed the pistons & rings, then it is a tough call on whether to replace the rings or not. If you had a lot of cylinder wall wear there would be a deep ridge at the top of the cylinder that should be ridge-reamed. If you skip this step and drive the pistons out, you risk breaking a ring land on a piston, which is NOT good.

If you replace the rings, you will need to hone to break the glaze on the cylinder walls or your new rings will not seat. You also need to clean any carbon out of the ring grooves in the pistons.

All in all, skipping the ring replacement will save a lot of trouble, but that is only a good idea if you KNOW that the rings are in good shape. My question is how did the bearings get worn out so far ahead of the rings?

 

I haven't pulled the heads off or moved anything yet all I've done is pull the caps off one at a time to measure the gap.
I think that this truck had very poor maintainance done prior to me getting it. I noticed the bearing issue due to the fluctuating oil pressure and the low oil pressure at a warm idle. The bearings are worn to the service limit in my hayes manual, that is why I don't think I need to do any crank work.
The oil pick up was plugged with what looks like old gaskets from the previous owner changing the pan gasket and timing chain cover gasket.
I didn't do a compression test before pulling the engine so now I think my only option to check the condition of the rings would be to do a leak down test.

Thanks for the tips about the hoses on the rod bolts, good idea.

 

Well the rings are the least of my worries. Did a leak test and had high(80%) leak by on three cylinders, pulled the heads, ones cracked.

On a good note the cylinder walls aren't scored at all and only have a small ridge, should be able to hone them and put the new rings in.

Now the question is how far to go on the rebuild, new cam, lifters and bearings too?

 

If the crank journals are not beyond service limits and are round, you could re-ring and minimize costs. Take a look at the lifter bottoms - you can use the cylindrical edge of one as a straight-edge. If the lifter bottoms are concave, it is time for a new cam & lifters. Maybe someone on these forums is up- or down-grading and will cut you a deal.

Be sure to get a good honing job as it will be very important for the new rings to seat properly. I favor moly-filled rings, or straight cast-iron for ease of reseating in an old bore, but I'm sure someone else can give you more options. (It is important to remove even a small ridge as the sharp edge on the new rings will hit the ridge - the old rings were slightly worn).

Good luck in picking up a new head or heads cheap.

 

I appreciate all the advice, now I hope I can talk the wife into letting me spend the money on it, we blew the auto budget on her new car(05 Taurus).

I can buy new heads for $230 each, a cam, bearings and lifters for $200, hone for $100, oh and need a cam bearing tool don't know how much that costs. I forgot to mention that the manifolds are cracked new are $120 each. I did find a set of hooker performance headers for $200,smog leagal for $480, kind of a no brainer there.

This $800 bill all of the sudden makes me think I should go get a loan and go all out on it.(last truck I did that on only got 6mpg but was a hell of a lot of fun.

Thanks again for all the help.

 

If the "new" heads have a good valve job on them, they are worth that money. I would not rush into cam bearings - you may not need to replace them for an overhaul. I would not buy the tool unless you are going to do a lot of engine building. Have your machine shop install the bearings while they are doing your machine work. You can cut a lot of costs, by shopping around wrecking yards and the classified ads here on FTE.

 

Do the heads from a carburated 86 351 fit an 88 fuel injected? Please tell me they do that will save me a ton of money I have a set I had a lot of work done to just waiting to put in a truck again. If not oh well.