3.2 rods... KOBOOF/OOG/OOH?

[nik97]

I have 6 3.2 rods from 3 different engines IIRC. 2 of them have "KOBOOF" casted into the side. 2 are labeled KOBOOH and the other 2 are KOBOOG.

My questions is this; can all the rods be used in the same motor provided everything is balanced?

 

[nik97]

Anyone?

 

[yzstud]

as long as they are balanced, i see why not
would it not be the same as spinning a bearing and replacing the rod that spun the bearing?

 

[gmorrell]

Balance is a given, especially if you're going to be combining them with some spendy forged pistons, I assume that's the plan?

It's far more important that the big ends be properly resized for the crankshaft rod bearing journal and rod bearing combination. If you don't get this right, the engine won't last 50 miles. Is this a machine shop buildup?

 

[LJRuddy]

... Those are the assorted sounds the rods make as they fly through your oil pan after a rod bearing failure at 7300 rpms... It really does not matter which rods you use in your engine as its more of a preference to what noise you want to hear shortly before you send your SHO to the junk yard.

 

[nik97]

Balance is a given, especially if you're going to be combining them with some spendy forged pistons, I assume that's the plan?

It's far more important that the big ends be properly resized for the crankshaft rod bearing journal and rod bearing combination. If you don't get this right, the engine won't last 50 miles. Is this a machine shop buildup?

I'm building the motor but the machine shop will balance the rotating assembly which will include forged pistons.

Correct me if I am wrong but, aren't all 3.2 rods going to have the same journal ID assuming they have not housed spun bearings?

I'm just curious why they have different castings on them.

 

[jthod]

... Those are the assorted sounds the rods make as they fly through your oil pan after a rod bearing failure at 7300 rpms... It really does not matter which rods you use in your engine as its more of a preference to what noise you want to hear shortly before you send your SHO to the junk yard.

I was thinking the same thing!

 

[1993MTXSHO]

hey, my rods were the best, mine said kabooi:laugh_ti:

 

[Lorenr]

Rods

The casting or in this case forging numbers don't mean much.

Measure the thickness of the original rods. The machine shop will do this if you cannot. Compare this number with the new rod. They must be the same.

Weigh the original rod and compare that weight with the weight of the new rod.

Measure the center to center distance of the original rod and compare this to the new rod.

Resize both the large and small ends of the rods.

If this s done correctly you should have zero problems.

 

[nik97]

After reading up a bit on rod resizing, it seems most people do it when changing rod bolts/studs or switching/swapping rods. I could see this being necessary when building an engine out of mixed parts. How necessary is it to resize rods out of an engine in decent condition like a used shortblock with original internals(junkyard shortblock)? No different than changing your rod bearings...

 

[yamahaSHO]

Everything changes over time. In addition, cycling heat will eventually help relieve many of the stresses (seasons) in metal parts. It is far better to bore out a seasoned engine than a new one. These rods should now be seasoned and have very little stresses left in them (aside from what you see on the surface). With a resize, they'll hold their shape much better now. Believe it or not, but the bores are not perfect right now.

If you want the motor to last, don't be cheap and have them resized. If your rod bearings aren't fitting correctly, they'll spin in no time. You're not dealing with the stresses of a stock motor anymore. You're placing MUCH more force on all your parts now.

I had mine flash ground, resized, shot peened and new bushings pressed and reamed for about $280 after tax.

 

[Brett]

After reading up a bit on rod resizing, it seems most people do it when changing rod bolts/studs or switching/swapping rods. I could see this being necessary when building an engine out of mixed parts. How necessary is it to resize rods out of an engine in decent condition like a used shortblock with original internals(junkyard shortblock)? No different than changing your rod bearings...

Sorry for the thread hijack, but i gotta ask.

I had a rod bolt break on me while torquing them after rod bearing install. I just took a bolt out of a 3.2 rod and put it in. Bad news?

 

[yamahaSHO]

Not the best idea. My machine shop wouldn't remove and replace a stud without resizing the rod afterwards.

 

[zak]

My guess is that the different letter codes refer to either big end bore or big end weight "as cast". This way when building an engine the Yamaha worker could select 6 of the same weight, or big end bore, rods. If the latter, he could have bearings meant to fit that bore.

My 0.02 - zak

 

[yamahaSHO]

I think they have more to do with the year they were made. Both Terry's and my '95 had the same numbers. I used one of his old rods on my rebuild to have everything match. I can't remember what it was, but I noted a difference between our '95 rods and some of Pat's gen 1 rods.