3cyl connecting rod question

gears · May 13, 2015

So I'm putting my 158 gasser back together, machine shop bored it .040 over - the ring gap is .012" (top compression ring) perfect new spec.

The crank was magna-fluxed and turned .010/.010 rods were re-bushed and re-sized. I checked the bearing clearance with plastigage and got .002-.0025" clearance on both rods and mains.

2 questions:
1. Does it matter which way 'round the rod goes on the crank? (I don't believe it does since it's all been re-sized and the rod bolts are inline with the beam of the rod).

2. There's what feels like an awful lot of play on the #2 rod when it's torqued. Side clearance is .010" , same as the other rods. Is it a matter of a larger journal (compared to a SBF) allowing .0025" clearance to feel almost sloppy? NOTE this is with just the rod attached floating in the bore (no piston installed).

thanks guys

Mike(NEOhio) · May 13, 2015

I'm assuming it's a 3-cyl. I&T manual says the rods are numbered and numbers should face the right side, away from camshaft. But also says they can go either way. The notch in the pistons must face the front. What do you mean by "play" on #2? And what's a SBF.

gears · May 13, 2015

Sorry about that Mike - Small Block Ford (289-351 family V8) uses 2.120" journal and I've never felt the rod twist while on the crank like the tractor is doing. I figured with a 2.748" journal diameter the correct clearance might be amplified to where it doesn't feel as tight as other engines I've done.

Only numbers on the rods are the ones I stamped in it when I tore it down. I marked the block when I did it but the machine shop re-punched them when they did the rods so I have numbers punched on both sides of the rods & caps!

The cast dimple on the piston crown will go in facing the front of the block.

Mike(NEOhio) · May 13, 2015

Did you mic the journals? If only one rod feels loose it may have been ground undersize. Then you have a real beef with the machine shop. .0025 is .0025 regardless of the diameter. If anything, it should feel a little tighter with the larger diameter because it's proportionately less. You mentioned new bushings in the rods. Were the bottom ends reconditioned? Could be out of round and you checked at the good spot.

gears · May 14, 2015

bottom ends were cleaned and checked but did not need/get cut. I'll torque and mic the big end before assembly. I don't think I've got a mic large enough to do the journal..... I've got a Mitutyo digital caliper though.

gears · May 14, 2015

So I just got home and LUBED and torqued the rods and they all feel the same now, a little wiggle but not the crazy "slop" I was experiencing with the dry bearings on the dry journal. Must've been the odd angle (Engine is sideways on the stand resting on on the back of the block)

3cyl connecting rod question

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Mike(NEOhio)

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