Piston Replacement

[mcpcola]

Ok I know about replacing all pistons when one is damaged but this goes out to all those who haved replaced one or two pistons I would like to know how you did it. Like my main concern is the rod bearings on the pistons that are replaced. My bottem end is damaged due to timing belt but right now i do not have the time to pull the motor for a complete disassembly i need to replace the pistons and rings with out removing the crank. The bottem end is in perfect shape and extremely clean. I am going to buy a built bottem end after the first of next year so it really only needs to last through the winter.

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[perley03]

By the looks of those pistons I'd replace all 4. You never know what kind of damage occured when they came up and smacked the valves. There could be cracks in the pistons that could cause major problems down the road. If it were me i'd pull the engine, ship it to a machine shop and have them mic every part over to see if it is out of tolerance. Then go from there. If the bore is within tolerance, go with standard sized pistons and rings. Also with some bent valves, you might want to have that head pressure checked for leaks or cracks. I only bent 4 intake valves when my T-belt went, but i had 2 cracks in those chambers, which lent me to looking for a new head. But, this is totally my personal opinion, so you might have different thoughts about things, but i always like to play it safe and do things once, and not have headaches later down the road.

 

[mcpcola]

I have picked up a new Head as the old one was shot.

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I am replacing all pistons with Top-Line Ceramic coated ones. My only fear here is taking the caps of the connecting rods to pull the pistons and putting them back on the crank with out damaging them. I only have a month to get it back together and no where near enough money at this point to have the entire engine prepped.

I guess what i want to know is if its possible to pull the connecting rods off the crank swap out the pistons and then put them back in using the original connecting rod bearings.

 

[perley03]

No, please do not use the old bearings. When ever you take off the caps on the rods, replace with new bearings. When you remove the caps, put some hose or tubing over the studs on the rods to protect the crank and the cylinder walls. Good luck with the process and keep us posted. And if you have any questions just ask we're here to help.
Shawn

 

[mcpcola]

No, please do not use the old bearings. When ever you take off the caps on the rods, replace with new bearings. When you remove the caps, put some hose or tubing over the studs on the rods to protect the crank and the cylinder walls. Good luck with the process and keep us posted. And if you have any questions just ask we're here to help.
Shawn

So even though i am not having the crank turned it is still ok to put in new bearings

 

[tom04841]

If you are just tring to get by till winter, there should be no problems with reusing the rod bearings. Just make sure they are VERY clean and use plenty of assembly lube when putting the rods back in. And also make sure you put the rods back in the same cylinder they came out of. I had to do a piston swap in a hurry and low budget, and have 50k on them after reusing them with no issues.

 

[mcpcola]

If you are just tring to get by till winter, there should be no problems with reusing the rod bearings. Just make sure they are VERY clean and use plenty of assembly lube when putting the rods back in. And also make sure you put the rods back in the same cylinder they came out of. I had to do a piston swap in a hurry and low budget, and have 50k on them after reusing them with no issues.

Thanks that is extremely help full I know this is not the right way to do this but that doesn't mean that it won't work. I planned on cleaning them well marking the caps if not allready marked and useing a good bit of lube and put them back in exact same way they come out but with new pistons and rings. I am affraid that if i put in new bearings which i have that they will wear out quickly and develop rod knock. I am going to put in forged parts sometime in february or march but I do not have enough time before it starts getting cold here and starts to snow to do a full build and my only other ride is a sport bike which is not going to see any winter riding so i need to just get it to run.

 

[half-cocked]

On the note of replaceing one piston, I have done it on a SBC and the engine is running very strong in a rock crawler FJ40. I know everyone says "These 4G63's are not SBC's and you cant do the samething." My personal opinion is why not, if your cylinder walls can be cleaned up and cross hatches are decent, put a new set of rings (I did replace all 8 sets on the SBC) and drop a new piston or two in. Pistons SHOULD never come into contact with anything other than the parts you put them on, i.e. rods, rings. Saying your breaking in your pistons is like saying you seating your bearings.

 

[GVR4592]

With the amount of force that the pistons hit the valves, the rod bearings could have been damaged. I would replace them, get some plastigauge and you can get a rough idea of what the clearances are. That way you know for sure if there will be a bearing failure.

Not that I reccomend doing this, but I've done it a few times. One time I was running to much nitrous on pump gas and I broke the ringlands on all of my pistons. I tore it apart gave it a quick hone, installed new pistons, rings, and bearings, and I was at the track that same night with no issues.

 

[bullettdsm]

GVR4592 is right (ouch that hurt). I have re-used rod bearings in certain situations. From the look of your impact, I would be hesitant to re-use those. The new bearings are not going to wear out quicker and give you rod rap. On the contrary, you stand a better chance of getting rod rap by re-using your old bearings. Bearings are pretty cheap from Bruce at partsdinosaur. Quick turn around also. One thing about plastigauge in this situation. You can literally have "dents" in your bearing that you may not be able see. If you do the plastigauge in an area that is not dented you can come out with good numbers. A possiblity to watch out for.

You obviously know about matching the rod caps etc. and heavy lube assembly on the new bearings.

Good luck with whatever you choose.

MB

 

[diambo4life]

Do NOT reuse your rod bearings.

 

[mcpcola]

I am going to get a complete master engine rebuild kit this is the one i am looking at and I will be using new bearings in the rebuild. I think this is an excellent price but i am going to see if they will swap out the pistons for 2G pistons and rings
http://cgi.ebay.com/ebaymotors/ws/e...m=200002304212&ih=010&sspagename=STRK:MEWA:IT

 

[chuckdog_5]

seems like a decent kit, if you go with the 2g pistons, you do know your going to have a lil over 100$ in maching work to get them to fit on the 1g big rods. not really worth it to me. im in the same boat trying to figure out what rods and pistons to go with

 

[BOBS90TURBO]

You can allways do what I just did,After blowing a ring in #2, instead of a quick rering, I got on ebay and found a stock used engine with 120k on it and good compression for $350 plus $250 for shipping, new T-belt equipment and headgasket with oem head bolts and I am good. And now I have the time to rebuild my bad motor the way I want.

Just another quick option.

 

[TSIfreek]

W T F is rod rap?? I want to know