REuse Piston rings

[SFerinTEXAS]

What to throw this out there. Thinking (maybe dreaming) of using a donor 78 79 motor to convert my XJ to the earlier spec top end including pistons. Want to keep eng and frame numbers intact. Can I expect to pull the pistons and save the rings? keeping each piston in its original bore in the transfer, can the rings be removed to clean the pistons and then be reused?

Doing some road test on the XJ (all stock) getting good mpg , close to 40 but to anyone who has never had a 79 to compare to the 82 there is quite a noticeable diff in the power . I do believe with the engine conversion along with the earlier TCI and timing advance the XJ will compete in my heart with the SF.
If i never had the 79 I would never have known the difference and then I Would Be Happy but NOOOOOOOOOO.

[DiverRay]

If you use the mechanical advance, pick up coils, and TCI as well as the barrels and head, it should work. I would hone the cylinders lightly, and reinstall the rings/pistons in the old bores. The BIG pickup is the advance, so keep that in mind.

[Geezer]

Reusing the rings is fine but I don't recommend any honing of the cylinders when reusing the original rings. It would lead to early wear.

Just be sure to keep them in their original hole and on the same piston...

Geezer

[SFerinTEXAS]

Thanks for the input. So DiverRay you think the advance retro would bring alot of the pizaaz back more than anything else? that is doable now.

anyone else feel free to jump in.

[Ivan]

I would venture to guess the head and cams are the major difference. Ignition can only be advanced or retarded so far, and I would guess a timing light would show minimal difference between the 10M and 2H7 setups. Although I could be wrong.

If I ever get the funds around, I would like to get a set of megacycle cams, just to see what they would accomplish.

You're right though, the early setup is much more spicy than the later ones.

[SFerinTEXAS]

So I have a new head gasket and I really would like to not change the pistons as that would be a major project I don't have time for anytime soon. I know the pistons are different and the compression is greater on the early models, and the chambers are smaller on the early models so maybe without changing piston i would recover a little of the compression with the early head. Hate to do all but the pistons and wish I had later.

[Ivan]

I was talking with TRBig last week about the very subject of early head on late pistons. He said that he used some clay in the chambers once and there was something like .15" clearance between the valves and pistons. I can't imagine the early head would have them over that much closer. In terms of combustion chambers, that's a lot of difference. My replacement 2H7 engine has a wrist pin knock and I only have 80 pistons to replace them, and I was concerned about the same issue.

[SFerinTEXAS]

Maybe before I do anything else I need to test the boost sensor. Hard to believe it's not working with the mileage I'm getting but after reviewing the advance info (thanks C_Bug) I will not do anything until I test it. If its not functioning correctly might explain my lack of Pizaaz.And dismay. Thanks everyone. Frying other fish right now so may be a week or so till I get to it.Had to decide which bike to set aside for a while and right now it's hands down the XJ. Still in testing- shake down with it, Got it a year ago this month and just jumped in on the restore a few months ago. So far so good.

Again ... anyone else want to add anything ... feel free.

[Poprock]

Put a YICS tester in the system. You'll probably want to test it for a really long time. Running one in mine and it improves power from 1500 up. I'm running a XJ top end on a SG.

[SFerinTEXAS]

I did the vac sinc with the tool installed (Thanks rpgoerlich). All went well. Engine runs like a sewing machine . The whole idea with my first post also included the desire to dispense with the YICS. Until I check the status of the timing advance I'm just farting in the wind. I've collected enough XS stuff over the years that I have quite a few options. If I thought blocking the YICS would MAKE ME HAPPY then I might consider it. Really rather it go away all together.