KB pistons

[aaronkeiser]

Yeah I'd wait on that pistons before you bore. It would probably work out fine but If you want it "dead on balls accurate"(My Cousin Vinny) You'd better wait.

[gradon]

So they bolt the HB and flywheel to the crankshaft and then perform the necessary "surgery" on the crankshaft to balance it? I plan on using a new HB and the 94 steel flywheel, but eventually go to Hesco's lighter-weight aluminum flywheel, so if it gets balanced to the heavier flywheel, will there be probs when I switch?

[Flash]

I just emailed summit to let me know when a uem-kb944020-6 kit will be available--guess in three weeks. So guys, is it smart to go ahead and have the block work done with the 3.895" bore(.020 over) w/o the pistons in hand? Also when balancing the rotating assembly, do they need the pistons and rods installed on the crankshaft or do they just balance the crankshaft and weight balance the rods w/pistons?

I would not have the cylinder bored until you have the piston on hand..........The Machine shop will probably tell you the same. As the final hone will be to fit each piston individually.......or at least a compromise between the smallest piston to the largest piston. Were talking about piston diameter....May only have .0001 difference between them or could have .0005 or more the machines need this info before he can bore the cylinder.
And other reason is piston expansion is different between materials and casting processes, and the machinist will need the piston spec sheet, to know what exact diameter that will need to be bored so the piston done score or worse, seize in the bore .................

Wait for what ever piston you decide on before you bore(short answer )

Flash

[John]

If you have a machinist who will bore and polish for a piston set that he doesn't have on hand, you might need a new machinist.
John

[gradon]

Well I haven't asked him yet, but I did ask him to press the pistons to the rods when I get them, so it looks like I'll be waiting a few weeks. I guess I can go ahead and get the oil pump, hb, water pump, and timing set while I'm waiting. The head is supposed to be done tomorrow, so I'll post pics of the finished head and maybe get the valves and springs installed(but not rockers, as I might need to buy new ones and shim them for the .020 that the block gets decked and whatever was taken off the head--hopefully he has a #). So should I drop off the crank, a hb, and the flywheel tomorrow, or wait until I have the pistons and bring them together with the block(does he need the block to make sure the crankshaft's good or does he need the stock specs of the crankshaft and then machine it to whatever will make the .010-.030 journals fit, should it need it?). I'd prefer to get whatever work done by the machinist that can be done while I'm waiting for the pistons. Edit: I traded a machined 12cw for a 4cw that "didn't need" machining, but had it's oil holes chamfered, so I might be able to use stock size journals. Also I haven't made the spacer yet, so that might be something that needs to be done and given to the machinist for the balancing of the crank.

[gradon]

So here was my email to Summit with their response(this was same day that dwg told us 3-weeks):

I don't know if you have heard from KB yet, but they just developed these pistons(the 944 and 945 line) for the amc/jeep engines. They told one of the members on our forum(jeepstrokers.com) that you would be carrying them(along with Jegs, Hesco, and others). Are you able to order a set of 6 of the 944s .020" over with rings? Please contact me when they are available, with correct specs and prices, and I'll be ready to purchase them. Thanks

"Hello. The part is still in development. They do not have a build date at this time. You can check back in about 3 months for an update. Thanks"

[dwg86]

3 months? Well, one of the techs at KB took my name and number and said he would call when the pistons are done so I can post the info here.

[seanyb505]

Yeah Id imagine its probly more complicated than just receiving the part and throwing it online for sale. Or at least thats what Summit is doing. Either way I would think Summit would tack on its own mark up to make some profit. Cant we order them straight from KB?

[Shark]

that sucks. why would that guy from KB email me with that one week stuff?

[gradon]

I see KB updated their site and has the pistons as Jeep 4.6l(instead of amc/jeep). The stroke has been corrected to 3.895(was 3.905) and the pin height is now listed as 1.353(was 1.358, so dunno which one is correct). They have the dish for both 944 and 945 listed as 60cc, so they still need to update that. Under Notes it says: "Uses 4.0L Chrysler / Jeep block and rods with 4.2L/258ci Jeep crank shaft. Match your original 4.0L crank flange and snout to the 258ci crank you'll be using." I'd email them but they don't provide contact info and I'm not setting up that mail configuration assistant that pops up when you try. Maybe you can get them to put in correct dish info dwg.

[gradon]

So Flash, I've read this elsewhere before, but it didn't sink in until I read it again tonight: "These rods(the Eagle CRS6150A3D) are for full floating pins, require custom pistons (or at least full floating) so standard pressed pin pistons won't work." So these won't work with the KB's, right?

[Flash]

So Flash, I've read this elsewhere before, but it didn't sink in until I read it again: "These rods(the Eagle CRS6150A3D) are for full floating pins, require custom pistons (or at least full floating) so standard pressed pin pistons won't work." So these won't work with the KB's, right?

I don't know if they are for a floating piston on not?......Do you have a set that you going to us?

If so look in the center of the rod (piston side). Is there a brass bushing in there or is it just a drilled hole??

[gradon]

I was looking around. Being on standby for these pistons is making me consider parts I didn't before/were pipe dreams before--lightweight clutch, roller rockers, the eagles. I was considering the eagles cause with them, I wouldn't deck the block(unless having the piston be .0015" above deck is OK w/ the .004" machining like the head got). This would also ease my mind about stock length pushrods and whatever rockers I go with.

[John]

I was considering the eagles cause with them, I wouldn't deck the block(unless having the piston be .0015" above deck is OK w/ the .004" machining like the head got). This would also ease my mind about stock length pushrods and whatever rockers I go with.

You would not be the first to build with the piston proud of the cylinder slightly. Not in itself a problem, but valve clearence must be carefully checked and compression considered.
John

[kris]

Any update on availability ?

kris.