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Pistons stuck


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So my new piston rings came in the mail yesterday and I installed them correctly onto the old pistons. The pistons were cleaned up and de-gunked prior to installation. Without rings, the pistons move very freely within the cylinder walls. After putting the new rings on I'll be damned if I could get the pistons to move at all. They are oriented correctly and in their respective order. I removed them, tried again with lots of lube and oil and they still don't move. With a ring compressor and deadblow hammer they fit right in but soon as they reach TDC, they don't want to move at all. What the hell is going on? I doubled check the boxed set that came, Hastings part # 665. :wall: With new rings I expect a tighter seal but this is ridiculous.

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I read that part in the manual where is tells you to check for ring gap. The instrutions that came with the pistons were fairly general and said some applications require the rings to be filed. Anyways I went back to the garage with my instructions and caliper. Both the old and new rings have the same exact gap when installed so no problem there. The instructions state:

 

"No portion of the inside diameter should protrude b eyond the piston land."

 

This statement is true for the old rings however NOT for the new ones. The width of the old rings is 4.4mm while the new ones are 4.6mm and protrude noticably past the land. So my guess is maybe the manufacter boxed the wrong size rings? This would make sense why the pistons have such a hard time moving is because the rings are too big.

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Have you rebored and honed the cylinders? If not it could be that the new rings get stuck when they reach the ridges in the cylinder made by the old rings at TDC.

 

If anything the top of the cylinder wall would be a minutely smaller diameter, so the piston would actually free up when it got past the top.

 

It's gotta be the wrong rings. 4.4 vs. 4.6 is a big difference when you're talking about clearances that get measured down to the 0.001". 0.2mm is ~0.0078"

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The ridges were removed so no hang up there. Only thing I can think of is the manufactuer boxed the wrong rings, maybe they are oversized who knows. Soon as I start my new job I may say "to hell with it" and just do a 4.0 swap. I have 3.55's and a 5spd so that would accomodate a 4.0 better I suppose. Guess I'll move onto interior work in the meantime.

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Soon as I start my new job I may say "to hell with it" and just do a 4.0 swap. I have 3.55's and a 5spd so that would accomodate a 4.0 better I suppose. Guess I'll move onto interior work in the meantime.

 

Keep in mind that you will need a new transmission for a 4.0 swap.

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Yeah, would need a new bellhousing among other things. Dang jeeps lol

 

Well yes. Because you need a different transmission.

 

The AX-5 WILL NOT bolt up the 4.0. There is no bellhousing for it, and if it did, the transmission would detonate.

 

You will need either a BA 10/5 or AX-15. But don't get the BA 10/5.

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the cylinders needs to be honed because engine is more than just wearing down the bore and rings. the top of the cylinder is has a larger bore than the bottom and the cylinder become oval shaped as it heats up and expands against itself. send it to a machine shop to get checked and re-bored or just honed.

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Well soon as funds permit, I'll either do a swap or just send everything to the shop and do a complete rebuild. Either way I was going to need to send the head in to be checked, I didn't like the color of a few of the valves. I suspect possible cracks.

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