Opinion On Keith Black Pistons

[RAMBLINFSJ]

I found these pistons at Summit. Summit Part Number is UEM-2225030-8. What's ya'lls opinion on these? What will compression be? Are they good quality? If anybody here has used these pistons, please give me your opinion. Thanks.

[jeepsr4ever]

Whats the dish on them? IIRC all KB pistons had a chevy pin hole and not a AMC pin hole.

[RAMBLINFSJ]

There discription is cast aluminum,Comp. distance of 1.580'', 4 valve relief, press fit wrist pins, pin dia. of 0.931'',and then the standard ring sizes. Under notes it says- Recessed head 0.190 inch deep x 3.600 inch diameter.

[1980_Cj7]

Shoot, we were planning on using the KB354 hypereutectic pistons next time around, but I just checked and MC is correct, you have to bush the rods to Chevy pin specs.

Plus, it's a little scary sounding about how critical the top ring clearance is and the extra heat that is built up and how the top land can be torn off the piston. They even have a pic of one that did that.

I think we'll be looking at some other pistons.

[jeepsr4ever]

There discription is cast aluminum,Comp. distance of 1.580'', 4 valve relief, press fit wrist pins, pin dia. of 0.931'',and then the standard ring sizes. Under notes it says- Recessed head 0.190 inch deep x 3.600 inch diameter.

:-|

[Rogue Racer]

The specs listed are the same as a replacement cast piston, like a Badger 362P or such. Nothing special, just an aftermarket copy of the original pistons.

If any of you have access to a regular Sunnen rod hone you can hone the Chevy pin size out to AMC size with no problem. Just be careful and measure often. The rod hone will take the material out of the piston in no time. You might have trouble talking a machine shop into doing it for you since that is not a "standard" machine shop procedure. Heck, nobody has imagination or adventure in their blood anymore.

[jeep_man_401]

I had a company make some bushings for my rods when I used the KB...in fact I told them I only needed 8 maybe 9 for a replacement. I got a bag with enough for another motor! :lo1l:

Price wasn't bad either. :t:

[jeepsr4ever]

The specs listed are the same as a replacement cast piston, like a Badger 362P or such. Nothing special, just an aftermarket copy of the original pistons.

If any of you have access to a regular Sunnen rod hone you can hone the Chevy pin size out to AMC size with no problem. Just be careful and measure often. The rod hone will take the material out of the piston in no time. You might have trouble talking a machine shop into doing it for you since that is not a "standard" machine shop procedure. Heck, nobody has imagination or adventure in their blood anymore.

:?: Dwight I have always liked your thinking

[82Waggy]

I had a company make some bushings for my rods when I used the KB...in fact I told them I only needed 8 maybe 9 for a replacement. I got a bag with enough for another motor! :lo1l:

Price wasn't bad either. :t:

Me too.

No big deal but it is an added expense - still cheeper than custom forged though - and a better piston for quench than the other off the shelf offerings.

[1980_Cj7]

Not finding anything that looks like a better alternative than the KB's. I wonder if KB could be talked into opening up the pin holes? I'm gonna ask.

[82Waggy]

Not finding anything that looks like a better alternative than the KB's. I wonder if KB could be talked into opening up the pin holes? I'm gonna ask.

Would be nice to know, but too late for me as I have already had my rods bushed. The pistons come with the wrist pins and spirolocks, BTW.

Let us know what they say.

[Rogue Racer]

If you are using 390-401 rods with the Chevy piston thing, then bushing the rod is about the only choice you have. You cannot hand hone .073" out of the piston and keep the pin bore perpendicular and true. If you are using 290-304-343-360 rods, then honing the piston pin hole to .931" is an option.

[82Waggy]

My 401 rods were honed open about .005 for a press fit on the bushings. The bushings were then honed as necessary for proper fit of the pins - we offset the pin bores a little to make all rods the same length.

[1980_Cj7]

Just talked to Jerry Ward at KB Silv-O-lite. He apologized for taking so long to get back to me. He was off, and all the other techs were at a show.

They cannot alter the pin size to fit the stock AMC pins. He said the pistons are made with a CNC program, and the whole program would have to be rewritten.

I asked if a machine shop could open up the holes. He said he would advise against that as there is not that much material around the hole and he thinks it would severly weaken the pistons.

I also asked if custom sizes like .035 were available. He said no, just .030, .040, and .060.

So, since these are the only hypereutectic pistons that I have been able to find for the 401 in a reasonable compression ratio, it looks like we'll have to bush the rods. I was hoping we wouldn't have to do that.

Well, at least now we all know.

[jeepsr4ever]

Just as I thought. :-|

Chevy pin .927
AMC 360 pin .930

Enlarging the bore .003 isnt a huge deal and can be done but if you run a 1.00" 401 rod then you have an issue. I dont know why they would even have pistons made to chevy pin specs when their wasnt EVER A AMC LENGTH ROD MADE FOR A CHEVY PIN......silly just silly :(:

[1980_Cj7]

I totally agree. He said that the pistons were originally designed for an AMC engine build-up some magazine or TV show or something was doing. Sorry, I forget the details. He said they specifically requested the pistons be made with Chevy pin specs, because Chevy pins were more readily available!?!?!? Soooo, that's how they designed them and still are to this day.

I was surprised when he said about the thinness around the pin, because the pistons are considerably heavier weight wise than the Ross forged pistons we used first time around.

This was all very disappointing. With all the technical advice, calculators, etc., on KB's web site, you'd think they have more options or be more accomodating on their pistons.

[82Waggy]

Bushing the 401 rod requires only a few thousands honing as well. Wish it was not necessary but the KB pistons and bushing process is still cheaper than custom forged with proper diameter pressed pins. The KB piston head is also much better for quench than any other off the shelf option.

[1980_Cj7]

Well I guess we are going with the KB354's.

So what I'm understanding is you hone out the rods to accept the bushings. How's it work from there?

a. Bushings press fit into rods and pins press fit into bushings?
b. Bushings floating in rods and pins press fit into bushings?
c. Bushings press fit into rods and pins floating in bushings?

[a440plus6]

Press into rods and drill oiling hole.

[82Waggy]

C

Once press fit into rods, the bushing is then honed for proper pin clearance - mine were fit with 7/10ths of one thousandth pin to bushing clearance.