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Balancing Manley Connecting Rods

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I'm balancing my rods now but have a few questions before I take the plunge and start grinding them. These are Manley I Beams for a 4G63 motor.

First question. The rods came from Manley with big end/small end weights written on each box. However, my measurements were different from theirs (not in a linear fashion). I did 15 measurements for each rod and averaged. Each of the 15 measurements were all very close to one another ( 1 to 3 tenths difference). Do you think the measurements written on the box are inaccurate or am I probably weighing incorrectly?

Manley Measurements - Big End:

Rod #1: 440.1

Rod #2: 441.5

Rod #3: 440.9

Rod #4: 439.7

My Measurements - Big End:

Rod #1: 439.6

Rod #2: 441.1

Rod #3: 440.1

Rod #4: 439.6

Second Question. From my measurements it looks like I need to grind off the following amounts. Does this seem like a lot of weight to grind off? When I balanced my pistons, they were only off by .3 at the most.

Big End:

Rod #1: 0

Rod #2: -1.5

Rod #3: -0.5

Rod #4: 0

Small End:

Rod #1: 0

Rod #2: -0.3

Rod #3: -0.6

Rod #4: -0.9

Sorry for the slow reply here. First of all I've never matched manufacturers exact weights for pistons or rods so it doesn't surprise me. You also need to consider the accuracy of your scales as this can play a part in your measurements. For our purposes of balancing components it's not the absolute value that really matters but the repeatability (ie we want to measure the same component and get the same result each time), so it's possible that some of the variation could be attributed to your scales vs Manleys.

1.5 grams isn't an unusual level of imbalance so this also doesn't surprise me. What you can safely remove is going to depend on the rod design though. If you're worried about the material removal perhaps effecting component strength then you could also opt to increase your tolerance slightly.

1.5g could be the difference between with fastener lube or dry. When i balanced my rods, i actually cleaned the rods out so I knew i was not wieghing fastener lube, which could be inconsistent.

Thanks for the feedback guys. I'm using the same scale and balancing fixture as the videos. I've made sure that the fixture is setup perfectly and have gotten consistent weights, so I'm confident that my measurements are correct. I've decided to balance big ends to .1 gram and I'll leave the small ends alone, since they are ribbed and I don't see anywhere that I could take off weight without compromising the strength.

My machinist balanced the crank, flywheel, pressure plate, pulley, etc... and said that the best that they could balance to was within .5 gram. I'd love to get everything balanced spot on, but from what I've gathered, I think I should be fine. I'll definitely try to clean the rods of lube and try reweighing them.

Attached Files

0.1 gram imbalance on the rods is probably a little tighter than you specifically need to shoot for but it's not going to be harmful if you get down that fine. I see your point about the small end design. I wouldn't be opposed to lightly linishing those ribs, however you need to remove material evenly from the entire circumference if you decide to do so. This will mean that the amount of material you remove from each part is minimal and it should have almost no real effect on strength.

Reporting back with good news! I removed the ARP lube from each bolt and was surprised that the lube actually weighed anywhere from .3 gram to .16 gram per rod. I re weighed all of the rods, then balanced the big and small ends. The amount that I had to grind was actually pretty minimal compared to the pistons since it's a steal rod vs. the lighter aluminum piston. Everything is spot on now and weighs exactly the same to a tenth of a gram. So juiced on this!

Few more questions though if you don't mind.

-Do I need to apply any oil to the backside of the rod/main bearings before installing them?

-I saw that someone else recommends wiping the cylinders clean with transmission fluid. Do you have any thoughts on this?

-Do I need to apply any oil to the cylinder walls when assembling the engine? If so, is there any specific oil you'd recommend?

-If I leave the assembled long block sitting while I fab up the rest of the car, do I need to worry about corrosion?

0.1g is being a little anal, IMO - variations in the oil splash and even lube may be greater* - but it won't hurt. As an aside, did you check the individual big end bolts separately first, I assume you are keeping them with the rods they were measured in, as they may have been part of the discrepancies?

*and variations in the combustion pressures from combustion chamber filling and port flow variations if a non-IR manifold and/or plenum are used. Heck, even if all the rotating parts are done that close, as soon as the clutch plate starts to wear, it will start to throw it out.

No, no, NO! Shells and their bores should be scrupulously clean - that contact is part of the cooling of the bearings. Different folks use different practices, but I will use an evaporative cleaner, run a bare finger over the bore and shell as the fingertips are very sensative and can pick up even a thou" nicks, etc, then another wash off. Again, different strokes' but I usually use a light smear of ROCOL (or other) anti-scuff engine assembly lube and a drop or two of oil to lubricate the bearings before assembly.

IIRC, they do that in the theory that the ATF helps 'float' any debris out that may be remaining in the honing grooves to be picked up by a LINT FREE cloth. Shouldn't hurt and anything that helps eliminate debris is a good thing, IMO. Again, different strokes' :-)

Some people will use a light wipe down of their preferred running in oil, some seem to drench it in engine oil, some Japanese engines are/were assembled dry. A general consensus seems to be to avoid overoiling because it can cause ring seal compromises on initial running until the oil is cleared out. can't recall rebuilding a diesel, but I would expect an excess of oil being a potential source of initial runaway - look on YT for what can happen when excess oil enters a diesel from blown turbo' seals... Might be bad practice, but I will usually just give the CLEAN bores a spray with WD40.

Going to depend on how long and the environment - oil or WD40 should offer good protection for the most part but in a more humid atmosphere, especially with large temperature variations that encourage condensation on metal parts, it may be an issue. Not something I have had to worry about, but there are things that MIGHT help - bagging up the engine and, before sealing the bag, purge it with CO2, Nitrogen or other inert gas - corrosion needs moisure and oxygen - and/or a moisture absorbing material which should bring down the humidity, such as some dried rice in a cloth bag on some plastic or alloy sheet that keeps it from direct contact with the engine. Regardless, what you MUST do is protect it from dirt and dust that might make it's way into the engine.

My recommendation is to use a clean mineral based oil to lubricate the cylinder walls. Everyone has their own personal preference but mineral based engine oil is effective and you should have a supply on hand during the assembly process anyway. As Gord mentions above, the bearing shells and bore must be clean with no lubricant applied.

Yeah, I thought that 0.1g might be a little overboard (my machinist was probably laughing), but it really didn't take anymore effort and I'll have the peace of mind knowing that it won't be an issue once the engine is fired up. I'll make sure that the bearings are clean, light coat of oil on the cylinders, and the only thing left to do is gap the rings and assemble. Thanks guys!