Hi all,

I'm rebuilding the 4.0L out of my 2000 XJ. I had the piston/rods assemblies in order when I took them out, but by the time I got them back from the machine shop with the new pistons on them they got all mixed up.

Is there any way to tell which rod was in which cylinder? or does it even matter which goes where as long as the piston is facing the right way?

Each rod has casting numbers on them and two letters stamped on the flat side of the rod, but there doesn't seem to be any discernible meaning behind them.

 

no.

 

Doesn't matter.

 

Sweet thanks guys, that's what I figured but you never know.

 

did they fit new bearings to a reground crank?

i would ask your questions to the machine shop that did the critical work b4 proceding.

 

No it's a stock crank with standard main and rod bearings. Just had the block bored .030" over and new pistons/rings.

 

then each rod fits one crank journal. any rebuilding instructions call for measuring bearing clearance with plasticgage. also to number the parts. i cant imagine your 6 rods and bearings matching the crank if it was not reground with rod bearings to match.

my opinion is you have a problem, hard to solve. dont know what to suggest.

i would ask your questions to the machine shop that did the critical work b4 proceding


did you keep the rod caps with the proper rods?, crucial. rod bearings? with each rod?

 

So the position of the rods matter or no?

I'm using brand new standard size rod bearings on a stock crank. Yes I did keep the correct end caps with each connecting rod, they are stamped on both halves so it would be pretty hard to mess that up. I measured oil clearance with plastigage and they are all within spec.

Assuming each rod is matched with a specific journal (which I'm not entirely convinced it is), I would be more worried about rod side clearance. For example if rod #1 was matched to journal #1 because it gave it a side clearance of 0.010", but if you put the #1 rod in the #2 spot it changed to side clearance to 0.020". In that case, yes I would be worried. But I think Jeep (chrysler) forged the rods separate from the cranks?

 

my concern was if they were worn they would need to go back the same . if new bearings then it should be ok if clearance is good . you originally just said pistons, not rod bearings.
i would still ask the shop. good luck.

 

Thanks for the input, I'll give the shop a call and I'm also going to measure the rod end play and make sure that's in spec too instead of just oil clearance.

 

Just plastigage and go.......

 

What you might consider in the future is to use a numeral stamp set to stamp each one as removed, I was taught this by a shop teacher in HS many yrs. ago (1963). They are cheap and have many uses in the shop.

 

this.

 

Agreed, and I do stamp my caps. There is just simply no reason not to.
Also ensured that the cap goes back on precisely the way it came off after the piston is pulled.


I don't know why anyone is suggesting he plasti-gauge? His machinist should have sized his bearings and instructed him which to order.

 

it's a vital step in engine assembly, not doing so is simply wrong and outright foolish.