Good morning folks.

Been like 12 YEARS since I've visited here, but the '80 4X4 20R's been running great since the rebuild back then.

But now, it overheated and then sat for 6 months, waiting to be repaired. An insidious pinhole leak in lower radiator hose occured, so no smoke or even smell. Just an almost unperceivable decel on I-5 with no accelerator pedal response. That's when I noticed the pegged TEMP gauge.

No oil or coolant was drained during this time, and the oil/coolant mix really damaged the cylinder walls and pistons.



After a hard time removing the pistons, and doing some initial light honing of these .50mm oversized cylinders, there's unacceptable gouging in a couple sleeves, #4 being in the worst shape & #1 being the best.

My question: What's normally done here to reuse the block, considering damage such as this? I ask because I really don't believe going to .75 over will be enough. Hopefully it will, but if not, What?

Thanks for any comments.
Steve

You can get 1mm OS pistons,but then you'd be at the very end,then you'd be stuck with resleeving. I've resleeved old tractors,not easy,but possible. There should be sleeve pullers available,but not sure on these motors. The sleeves are then frozen for a long time,and slip in with minimal beating. Hope this helps.

Thanks much.
Took the block in to the shop yesterday. Hopefully the damage can be covered by going 1.0 over.
They gave me the bad news on the head that I took to them earlier: Warped on top! The cam didn't want to rotate when I dismantled it, but didn't give it much thought at the time.

Overheating these motors is not a good thing.

Steve

I'm not familiar with your motor,but if it has cam bearings,the journals can be align-bored to remove the warp and different bearing shells fitted. It may require thinking outside the box,but I've found bearings to fit really rare motors,such as a really old Royal Enfield engine I rebuilt years ago.

Thanks for that comment.

I did wonder about that too. Why wouldn't the shop think about line-boring the head/top shells to oversize, and maybe turning down the cam's journals, in order to accommodate bearing shells? Too costly? Maybe. But, not quite like a Enfield engine, these 20R heads are getting harder and harder to find. Quite a few 22R heads are out there, but I don't believe they are compatible with a 20R block.

Steve

I did read about a 22r modified with a 20r head[open chamber] to produce about 1100 Hp! The 20r head had to be heavily modified to fit. bearing shells come in an amazing variety of sizes and widths and a fairly good automotive machine shop[dying breed,only one near my house is 100m round trip]can fit bearings to your head. If warped on the block side,the absolute minimum should be shaved off. In the event of over decking,there are copper shims to use with the gasket. I had to put one on my '88 P/U,which measured 185psi after a head repair.

Wow! No problem there!

Thanks.
Steve

Yes,maximum compression is supposed to be 171,and with the shim it measured 175,and I've not had a problem yet except a wrist pin noise. 350,000 miles is a lot,and I've not been easy on it.

That's quite a few miles for sure. That compression is something for me to shoot for. Thanks.
Called the machine shop yesterday and yes, they were able to bore the cylinders. I failed to ask them to what dimension (.75 or 1.0mm), as I was just elated that they were able to do it. We'll find out.

Steve

If your local machine shop cannot or will not line-bore the cam bearings to fit available bearings,find a shop online that can think outside of the box and fix your head. I know that this can be done,as some aluminum heads without cam bearings have been bored to accept bearings,either standard shell bearings like main and rod bearings or solid bearings indexed with a dowel. The solid bushings can be machined from a piece of bronze to fit into the head.either way should get you back on the road for a long time. Good luck with your project,and post results so that others in your situation have an alternative to buying a possibly impossible to find,and expensive head. This was done with many ancient motors with pour in place babbit bearings so that one could use shells instead of having to pour metal and ream to fit the crankshaft.