304 Engine Ring Question.

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My son has a '74 CJ and the right bank is smoking. We are going to pull the valve cover on Tuesday and check to see if the drain back holes are clogged as well as putting new valve stem seals in and checking compression.

My question is (since he doesn't have much money after buying etc.) if we find a bad cylinder, can we just pull that piston and replace the rings?

Also, would we have to pull the intake or can we get away w/leaving it and re-sealing it up (that is if the valley pan doesn't give way).

Thanks,
Jim

[tufcj]

You can pull the piston, hone the cylinder, and put new rings on it. If there's a ring ridge that you can catch a fingernail on, then you'll probably need to run a ridge reamer through the cylinder too. A ridge left at the top can break the new top ring. You'll need a groove cleaner to get the carbon out of the ring groove before installing new rings (a broken piece of an old ring will work). Remember that pulling the piston requires pulling the pan. Getting a pan gasket in and sealed on the bottom of a motor can be difficult.

You can get the head off without pulling the intake, but you'll never get the head back on and the intake sealed. You're better off just pulling the intake and buying a new $20 gasket and avoiding the hassle.

Bob
tufcj

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Thank you Bob, we will see after we do a compression test.

If we are down that far maybe we should re-ring them all but not sure what rings to buy either.

We will see. Sounds easy enough.

Thanks again for all the help,
Jim

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Bob, should we change out the bearings on the crank (where the piston attaches) or just leave them since we won't be turning the crank?

Thanks again,

[tufcj]

How many miles on the motor. You can change the rod bearing just to do it, or you can look at it once it's out and make your decision then. Any scratches or copper showing, replace it.

The 304 that was factory in my Jeep dropped a valve at a little under 60K. Valve head broke off and the stem punched a couple of holes in the piston before bending over 90 degrees and jamming in the valve seat. Had just one head redone, replaced one piston/rod (with rings and bearing). Ran it another 40K before I was given a 360. Put it on a stand and took it apart. It had just over 80K on it. Had the heads done at a shop, cylinders were still within spec, so I honed them, did new rings on the factory pistons and main/rod bearings (all standard) dropped in a new cam/lifters/timing set. I ran that motor another 50K, it was in my Jeep when I sold it. Still used less than a quart of oil between 3000 mile changes.

Bob
tufcj

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Well ACCORDING to the odometer he has 87K on the 304.

I need to find a simple easy rebuilding book to read, been a long time.

I talked to the machine shop and 1200.00 for a short block & 1800.00 for a long block rebuild - ouch.

Short block seems ok (but may need parts?) but then the heads won't be decked to match the block UNLESS the gasket can take care of that?

Going to talk to the kids and see how they want to go. He is jonesing to drive his Jeep he just bought but he will get a ticket for helping kill mosquitoes :)

[rsbad454]

Yes indeed, AMC engines aren't cheap to build. I probably have 3500-4000 into my 304 and it's stock.

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Agreed.

We are going to tare down Jr's 304 and check the cylinders/taper etc, if ok, then we will just re-ring it for now from NAPA.

[rsbad454]

Here is mine as of right now..

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SWEET !