4.1 rods heavier than 3.8--which to use??

[turbojack]

Took my block,crank,rods to machine shop,& the guy noted that the # 763 rods from the 4.1 had heavier caps ( more meat at the flat part on the bottom) of the rod cap,as compared to the # 763 turbo 3.8 rod caps.What gives???You see I only have 5 of the 3.8`s and a full set (6) of the 4.1`s.I like the idea of the lighter rods (3.8),but will they hold up to a 4.00 bore 4.1 ??I need to know this cause we`ll have to lighten one (4.1) rod to have a set (6) of the 3.8`s.By the way my crank is a turbo crank.---Any input will help,,,,,Jack

 

[cool 84]

I'm extremely surprised there's a difference. My 4.1 had the usual 763 two dot rods and I didn't bother comparing them to the old (bent) 3.8 rods but you can bet I'm going to. Are you sure your machinest is right and maybe the 3.8 rods were previously balanced making them lighter? I know balancing is done by removing metal from the part of the rod you mentioned. To answer the question, the block will give up before the rods, there should be no problem.

 

[turbojack]

4.1/3.8 Rods

I looked myself,& shure enough,about .025 or so bigger,thus making the rod heavier.I told him to use the lighter 3.8`s & shave the 4.1 so I will have 6 Identical rods.Lighter rotating mass!!He wont do anything till I get all my ducks in a row.This block must be a later version,has .625 oil feed holes.Any way machine shop going to balance whole eng.-------Jack

 

[turbojack]

4.1/3.8 Rods

Just talked to the guy that I bought those 4.1 JE pistons from & he said he used the 3.8 Rods & had the whole eng re balanced.He was running 4.1 bored & stroked to 274 cu. in. Didnt say any thing about 4.1 Rods heavier,he just used the 3.8`s.Ran it for 8000 mi,no problems.Turned 10`s 1/4 mi.-------Jack