Attempting a motor rebuild

[Captndrydock]

My ol '77 Chrysler 135 has dropped compression down to 125 from 150 psi in the bottom cylinder. I took the head off and the gasket seems fine, but the piston has quite a bit more play when I rock it side to side. Looking from the transfer port, the top ring seems very loose and I can see the ring has side to side movement inside the landing. That is, it seems more wallowed out than the others. I can see space on either side of the ring as I push it. What causes something like this? As far as I can tell, the ring is not broken and the cylinder walls are in pretty good shape.

So I've decided to restore and rebuild this motor and trying to learn all I can before I begin. My factory service manual leaves out a lot of detail. Is there a factory rebuild manual? I've searched online to no avail. Any tips or suggestions are appreciated. Or if anyone can point me to videos or other forum discussions, that might be helpful. Or just general discussion in this post...

Btw, this is for the fun of it, as much as anything. I have 3 other smaller 4 cylinder Chrysler motors that run fine, but they're not the 135hp. I'd like to restore this motor to like new condition, paint and everything. It was original to my boat that is also fully rebuilt and restored.

 

[airshot]

To start, you need to take things apart, then get an inside micrometer or a dial bore gage to check the bore and see how round/ out of round each cylinder might be. Probably will need to be bored oversize so pistons and rings will need purchased to match the new diameter.

 

[Captndrydock]

Thanks, yeah I figured it would need to rebore/hone. There is some light scuffing, but no obvious gouges that I can see. And almost 50 years of use, so it could well be a little out of round. I'd like it to be tight and like new when complete. Need to find a reputable machine shop.

 

[rolmops]

After fifty years of use, you might want to resleeve and really get a great engine

 

[Captndrydock]

After fifty years of use, you might want to resleeve and really get a great engine

Is re sleeve better than rebore/ hone?

 

[rolmops]

Is re sleeve better than rebore/ hone?

Re sleeve will get you back to the original size. It is a good idea when the cylinder has been oversized before and when over seizing does not make practical sense because the cylinder walls are badly scorched. At least here where I live there is not a great price difference between the two. I am not so sure that Chrysler parts are still available. It has been a while since mercury bought them out

 

[racerone]

Pistons and rings appear to be available in 0.030" O/S

 

[Captndrydock]

Re sleeve will get you back to the original size. It is a good idea when the cylinder has been oversized before and when over seizing does not make practical sense because the cylinder walls are badly scorched. At least here where I live there is not a great price difference between the two. I am not so sure that Chrysler parts are still available. It has been a while since mercury bought them out

Oh Chrysler parts are available if you know where to look.

 

[Captndrydock]

Well I just removed the head yesterday. I'll get the motor off the boat , disassemble and send updates of progress! Might be a couple of months as I research more and get all the replacement parts together. Thanks all!

 

[Captndrydock]

Re sleeve will get you back to the original size. It is a good idea when the cylinder has been oversized before and when over seizing does not make practical sense because the cylinder walls are badly scorched. At least here where I live there is not a great price difference between the two. I am not so sure that Chrysler parts are still available. It has been a while since mercury bought them out

Pretty sure this motor hasn't been rebored, but we'll see! Thanks!

 

[jerryjerry05]

Not sure you can re-sleeve this motor.
Parts are available. Check Wiseco pistons. I've had good luck when I use them.

 

[The Force power]

My ol '77 Chrysler 135 has dropped compression down to 125 from 150 psi in the bottom cylinder. I took the head off and the gasket seems fine, but the piston has quite a bit more play when I rock it side to side. Looking from the transfer port, the top ring seems very loose and I can see the ring has side to side movement inside the landing. That is, it seems more wallowed out than the others. I can see space on either side of the ring as I push it. What causes something like this? As far as I can tell, the ring is not broken and the cylinder walls are in pretty good shape.

Can you post pictures?

 

[Captndrydock]

Not sure you can re-sleeve this motor.
Parts are available. Check Wiseco pistons. I've had good luck when I use them.

Thanks Jerry, Yeah, I plan to rebore/hone anyway. Yes, Weisco is also what I've heard is best.

 

[Captndrydock]

Can you post pictures?

l'll be glad to post pictures or videos. I need to figure out how to do that in this forum first. I already have quite a few pics and vids and I'm sure to have more!

 

[jerryjerry05]

Just remember to buy the Wiseco wrist pins and rings. They won't work right unless you do.

 

[racerone]

They come in a kit with wrist pins and rings as far as I know.

 

[Captndrydock]

Can you post pictures?

https://www.facebook.com/video.php?v=3590424351248561

 

[The Force power]

https://www.facebook.com/video.php?v=3590424351248561

IF.. that is the only piston that shows "symptoms" I would remove the carb. / Intake and from that end remove the end-cap of that particular piston/rod.
and see ???

 

[racerone]

That looks to be the wrong style piston ring.----I would not hesitate to take this motor all apart !!

 

[Captndrydock]

That looks to be the wrong style piston ring.----I would not hesitate to take this motor all apart !!

I don't think this motor has ever been apart, judging by paint on gasket edges and bolts. I have a friend online that thought the piston wasn't a true high ring piston. Hard to say for sure. I'll know more when I get it out. I'll post pics...