scuffed pistons, starting over

[Flash]

They thought the 4.2 had a deck height that was higher, right. So that gives that piston more pin height, more stable in the bore at BDC? I have been reading the KB 944 thread and am going with those pistons this time. They may have gotten them today after I left. I don't have my 4.0 rods anymore so will get those and then get the #s we've all been waiting for.

What year is you motor?
Any and all the info you can give us on them I/we would appreciate.

Flash

[gradon]

Summit quoted me $478 on the pre-order(before I found out about a ktm kit that includes the rings). Realm got his "backdoor" from a KB rep who obviously was above their "sell only to distributor" rules(kudos), but kept it a shade below their MSRP. If you can't have them at your doorstep for <$500, then KB has wasted their time and energy on a product that not many people will buy, IMO.

[highstumpr]

I called summit and got the 684.00 or so number so got them thru napa for 667.00. I wanted them so I bought them, I don't know any sales reps to cut me a deal.

[4point6]

Where are you getting the KB's from. I just went to summitracing.com and entered uem-kb944030 in thier search. It came up with set of 8 pistons for $917.00!!!!!!! Something is wrong because it should be 6 piston set. If thats right, 917.00 divided by 8 equals 114.00 per piston. That would be $684.00 for a set of 6. I read someone got them 450.00... Where???

I just checked Summitt, searched for UEM-kb944* - 4 results:

UEM-KB944020-6 SET OF 6 PISTONS $478.69
UEM-KB944060-6 PISTON SET OF 6 $691.39
UEM-KB944040-6 PISTON SET OF 6 $691.39
UEM-KB944030-8 PISTON SET OF 8 $917.99

[Flash]

Didn't KB say that the .030" piston was all that was available for now????????(UEM-KB944030)

Definitely likening the the .020" oversize piston price But thats still $80 each!

This one has got to be a miss print UEM-KB944030-8 PISTON SET OF 8 $917.99 unless they have NO intention of
Selling any of the .030"

Flash

[dwg86]

At those prices they won't selling many...just my opinion.
When I started looking at stroking my Jeep engine, the one thing I liked was the fact that you could use off the shelf parts and build a real torquey engine at a reasonable price. Now, I know its better to use a longer rod on any stroker engine, because the longer stroke pulls the piston lower in the cylinder, and a longer rod will help reduce side loading the piston. But using the 258 crank and rods was done by AMC. The way I see it, and I may be wrong, by using the 258 crank and rods in the jeep 4.0 block(still basically the same block as the old 258), its almost like running a big bore 258. Also there is only a slight differance between the rod ratio using the 258 rods and the 4.0 rods, 1.51 vs 1.57 .
It seams that most people that have had problems with thier "low budget" stokers, at least from what I have been reading, is not the bottom end, but with cams lobes flattening out. All those small metel paricals floating around in the oil could have contributed to the piston scuffing problem.
If It was in my budget, or I was building a high HP engine, using nox, blower, or turbo engine, I would use the forged piston. But for a 250HP daily driver??? I can't see spending $80.00 to $100.00 per piston when I can spend $20.00 to $30.00 a piston. Right now I am more concerned about cam issues, wihch hopefully will be taken care of soon.
Sorry for the rant, but $667.00 for an "off the shelf" piston (with a poor quench) is not a good price (I am very disappointed). When you can get 8 sbc or 8 sbf pistons for half that price. Stepping off my soap box now.

[highstumpr]

I think the rod bearings not being notched has to be a factor in my case. The guys at the shop didn't seem to concerned or willing to notch them. What size should the hole be and should I file it or use a little die grinder? My cam was just starting to die, maybe getting more oil than some from the 300,000 plus miles in the lifter bores. I'm going to use cam savers this time.

[dwg86]

I think the rod bearings not being notched has to be a factor in my case. The guys at the shop didn't seem to concerned or willing to notch them. What size should the hole be and should I file it or use a little die grinder? My cam was just starting to die, maybe getting more oil than some from the 300,000 plus miles in the lifter bores. I'm going to use cam savers this time.

If you look at the rod and cap you can see the hole where the split line is (cap and rod seperate). A small die grinder might be easier but a small flie would work. Make the hole in the bearings the same size as the hole in the cap/bearing. I would NOT put the bearings in a vise, hold them in your hand, and make sure to clean them real good after you are done (I use spray brake or carb cleaner). Also clean the block and oil passages real good. I use engine degreaser and hose it out, dry it with compressed air and put a light coat of oil on bores and surfaces where the main bearings go to keep them from rusting. When you put the main bearings back in the block, wipe the oil from the block bearing surfaces before installing the bearings.

[highstumpr]

The pistons came in today, KB944.040, they sure are pretty. Will bore the block first of the week, it's a 92 HO. Should have the rods and bearings ready to go in and by mid week then see where we are. I think we decked it .015 last time hope we're not to close already. I hate just waiting around. On the BDC idea, I still don't have a block to look at but a sleeve for the 4.2 is right at an inch longer than one for a 4.0.

[highstumpr]

Well I kept searching and found that "oleshot" answered my BDC question back in oct 07 in the yahoo group, thanks. It's about only .050 less piston in the hole at BDC.

[dwg86]

Well I kept searching and found that "oleshot" answered my BDC question back in oct 07 in the yahoo group, thanks. It's about only .050 less piston in the hole at BDC.

What was the question? If I may ask... What did you pay for the .040 KB pistons, and where did you get them?

[Flash]

I when back to the first page and found the question, but wouldn't mind hearing the answer too


Flash.

[gradon]

The question is "How much lower in the bore @BDC is the piston using the 4.2 rods(compared to stock setup)? The answer is .050"?

[highstumpr]

that's the difference between the different rod/ piston combinations not the stroke, which would be another .242 (half of the .484 stroke increase) out of the bore.

[gradon]

So one piston is .050" lower(in add. to the .242") due to the different pin heights?