KB Pistons

[1980_Cj7]

Got our new KB 354 pistons, and the bushings from Diamond Racing to adapt the Chevy sized pins that come with the pistons to the AMC rods. MAN, there sure ain't a lot to these bushings! And on top of that, they don't go over the pins, so will need honed out and get even thinner than they already are!

KB said the piston holes can't be opened up to fit the AMC pins without seriously weakening the pistons, but looking at them, and the bushings, it sure seems like they could be opened up that much.

It just seems like there isn't going to be much left of these bushings, and I'm wondering how they're gonna hold up.

[82Waggy]

Bushing rods is common practice - don't worry.

[jeep_man_401]

Got the same thing in my 401...no problems.

When they make something that thin to press into the rod, they are going to distort some and need honing to fit anyway.

Heck they even sent me evough extra to make another motor!

[jeepsr4ever]

Your bushings can get as thin as .028" after final honing and will look like paper in some applications but if they are done right they will last and in your overkill situation should last a long time :D

[Blown7]

Yep mine are only a .005 thousandths wall.

Jeff

[1980_Cj7]

Thanks for the replies and reassurance guys. Never having been there or done that, I was just a little worried. Now I can sleep again. All's we need is the new dizzy gears from Matt, then we can haul all these new parts to the machine shop and hopefully get the show on the road.

The only little glitch yet is I told the shop when they determine what size bearings are needed (they are just getting them themselves, if they don't already have them in stock), I want to pick the rod bearings up from them and mod them with the oil squirter holes. I'm counting on them not forgetting about calling us to pick them up and do that.

[82Waggy]

One other thing you might think about,

When I had my rod bushings installed, They were honed on a mill. A fixture was used so that each rods' journal to wrist pin length came out the same (real close anyway) - in other words the center of the bushing may have been offset honed a couple of thousandths to adjust for any previously existing rod stretch.

You will probably end up with approximately 30 thousandths bushing wall thickness: 1.0001 stock pin diameter less the .9272 KB wrist pin diameter yields .036 wall bushing. Actual bushing diameter is a little larger than 1.0001 - the rods will be honed open for a press fit and the bushin ID will be honed for roundness and pin clearance ( I think my pin clearance was .0007 [7/10ths of a thousandth]).

[1980_Cj7]

Good point. I'll mention that to the machine shop.

One other thing, do I have to do anything to get oil to the pins now that they will be free floated? Fuzz mentioned something about drilling holes in the ends of the rods, but I'm not sure where/how, and didn't get down to see him yet and discuss...or look at samples in his "401 Museum", ha, ha.

[82Waggy]

One other thing, do I have to do anything to get oil to the pins now that they will be free floated? Fuzz mentioned something about drilling holes in the ends of the rods, but I'm not sure where/how,


Well, some drill holes, or groove the bushings, or whatever, and some don't do anything at all.

My guys elected not to drill any holes or do anything else. They don't drill oiling holes for the bushings in the rods of any of their blown, nitrous, alchy, or nitro motors either.

[82Waggy]

I posted a pic of my floating KB pistons in a new thread.

[1980_Cj7]

I posted a pic of my floating KB pistons in a new thread.

Yep, already saw it. Thanks. I don't miss much in here as I watch religiously. Just waiting to hear from the machine shop at this point. Once they figure out what size bearings we need and get them, we want to pick them up and make the oil squirter holes/notches in them.

I did discuss matching up the rod lengths when they hone for the bushings and they said yes, that is part of what they do when they recondition the rods.