258 Connecting Rods

Joseph.smith54

New member
Being my first rebuild, I expected to make some mistakes. The first big one that I noticed was not matching my rod caps with the rods after taking them out of the block. All of them are stamped but three of the rods and caps all have the number "3" stamped on the side. The others are 1,2, and 4. When figuring this out I also noticed that only one of my rods is a 707 (#4) and the rest are 352s. Just from the little research that I have done, I believe 707s were stock. Any insight?
 

I cant help at all, I've never rebuilt an engine... YET!!, but its coming.
 
The 707 rods were built from 71 to 82. The 352 rods were built from 82 to 87. Some one has been into your engine before.
 

Well joe , looks as though a phone call the machine shop will be in order. If the mains and connecting rod caps were mismatched prior to your disassembly , block will need to be align bored and the rods resized and this will mean oversized or custom bearings but the bearings are no big deal , it's the machine work expense , as you know. Got to sort that out before bearings are ordered , that's a must . I know you want this engine , and the whole jeep for that matter , done right , so , at the minimum , all parts of the rotating assembly ( rods and main caps ) will at least have to be gauged . But usually this works out to the align bore job and resizing the big ends on the connecting rods . I know you'll get your prices first but your machine shop guy is really reasonable and that's great ! Machine shop work is always known to be $$ .
I knew from the earliest pictures of the engine that work was done to it but this time around you'll get it right . No fear . I'm sure the shop will stamp the block and mains , rods and caps correctly on one side to match for future disassembly if needed . Always good if you decided to replace bearings with the engine in the jeep and the oil pan off to do a fresh up bearing replacement . Happens more often when a manual trans is used . Bottom ends just work a bit harder with a stick . You'll definately want to plan ahead for this and be ready for that future swap if need be .
Once the gauge and/or machine work is all done , the plastigauge will have the final word on calling it good or not. When properly cut and sized , the only adjustment is bearing clearing clearance and sometimes you got to over or under size if need be . But we'll see how that works out , possibility since this engine had some work done before . But maybe we'll get lucky .
I got faith in your machinist as long as your happy with him.
 
I did notice that all of the rods and rod caps were stamped when I dismantled the engine but I didn't notice the three that had the same numbers on them. I do plan on giving the shop a call to see what they advise. I'm hoping that they have a set there. If not then I'll be looking for used set at first and if I can't find a reliable set then I know jeep4x4center.com sells some for $30 a piece.
 
When i built my engine my rebuilder guy recomended shaving the mating surfaces of the rods and caps and doing so it makes the crankshaft bore smaller and needed to be rebored to standard. This makes sure that everything lines up the way it should. I don't remember how much that was but it wasn't very much. You might want to check on how much it would be at the shop you use. This way it won't matter if you get the caps mixed up.
 

When i built my engine my rebuilder guy recomended shaving the mating surfaces of the rods and caps and doing so it makes the crankshaft bore smaller and needed to be rebored to standard. This makes sure that everything lines up the way it should. I don't remember how much that was but it wasn't very much. You might want to check on how much it would be at the shop you use. This way it won't matter if you get the caps mixed up.

Although I've never tried this myself , it is done by machinists to true up the mating surfaces as you've stated . To my knowledge it's done on a wet stone , a large stone used to hone knife blades and such with a lubricant such as 3 in 1 oil . I would say you would have to be confident that your removing equal material from each end of the cap and conversely , each end of the rod as well to keep the mating surfaces true . Theoretically , that should accomplish what the actual machine does to square them up so the bearing shells will sit evenly. The sides of the rods are done too so that proper measured side clearance between two rods on a journal are correct .
Of course this is not for the faint of heart so you'll probably want a set of rods that you don't intend to use on a build to practice with until your talent has been found . A little at a time I guess and clean off shavings and oil to test fit on the crankshaft . Hey , if you get good at it , you could save money on machine shop cost . Low overhead too , just a stone and some oil !
the last small block we rebuilt had the rods balanced as a part of the crankshaft service and this step was already performed by the machinest but yes , he cautioned to check side clearance and if clearance was needed , use the wet stone and oil. Time consuming but will make you feel less worried at break in time and many miles after. It should be mentioned that these clearances need to be checked for accuracy with the rotating assembly actually assembled and not just test fitted on the crank out of the block . That will of course be when it counts.
 
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