KB Hyper Pistons

[oldskydog]

Does anyone have any experience/opinion on the KB Hypereutectic pistons? I took my 67 Nova 327 to the machine shop in hopes that I could just break the glaze in the bores and re-ring the original L-79 forged dome pistons but alas, it was not to be. Too much clean up required so it had to go to .030. I now have to get new pistons and since it will not be raced or run too hard I'm looking at the KB Hyper pistons with a .100 dome to keep it near the 350hp specs. I couldn't find an off the shelf 327 forged domed piston without spending big bucks and I don't want to go to flat tops. These are supposed to give me 10.5 to 1 with the original 64cc 462 heads. I'm also using an original GM 350hp hydraulic cam that is in good condition so no break in problems (I hope).
Any comments/suggestions?

 

[bubbletop1961]

I have used kb's in my last 2 motors. The motor I have them in now is a 9:1 set up for turbo. NOT the choice for most people doing forced induction, but, I never seem to have extra money so its what I could afford at the time. I have been very happy with them and have nothing bad to say about them. Tuning a carbed turbo car was alot of fun. Although it wasnt easy for someone thats never done it before. They lived thru a lean condition right off the bat. Then way rich. Then my timing retard wasnt activating. It was only 6#'s of boost, but it was 6#'s of boost with 32 deg of timing. I was trying to have 22 deg under boost. Made 3 passes at the track and who knows how many times I romped it around town. They seen 13#'s of boost max. now the motor is n/a agian and is still running good. I would say my experience is very good.
but that said. I've always heard they are more brittle than fordged. Get into detonation or a bad tune and the break. Just what I've heard.

 

[1958 delivery]

I don't know if they have been improved at all since first introduction. But I've seen too many break for what they cost. I always felt they were nothing more than over priced cast pistons.

 

[models916]

Federal Mogul

I used Federal Mogul version of the silicone cast piston (10:1) in my last stroker sbc. I beat the daylights out of the engine on a regular basis and experienced no problems. The guy I sold it to uses it in a 4x4 off road racer and it is still performing well. State of tune is more critical on cast pistons. Timing, jetting, oil infiltration (detonation) will break the tops of the piston. I think they are rated for MILD performance use.

 

[Ronnie Russell]

Ihave used the Fed mOgul hyper pistons models referred to in several dirt track motors. No breakage, and nobody is tougher on parts than those crazy dirt-trackers.

 

[1958 delivery]

Most all that have broken have been the very upper edge. Probably from detonation. And there's probably a heck of a lot more that don't break. Personnally, I choose to spend the little extra and use forged when it's a good Hi Perf build.

 

[oldskydog]

Thanks for all the input guys. I have decided to give them a try since this is a resto build and not a performance build with just an occcasional romp on the street.

 

[bubbletop1961]

Youll do just fine with them. I would do it again.

 

[1958 delivery]

Thanks for all the input guys. I have decided to give them a try since this is a resto build and not a performance build with just an occcasional romp on the street.

Out of curiousity, how much are they?

 

[models916]

Summitracing price

Pretty cheap.

http://store.summitracing.com/partdetail.asp?part=UEM-KB193030-8&autoview=sku

 

[1958 delivery]

Looks like about $200 vs $320 for forged.

 

[models916]

Wish!

Don't you wish 409 forged pistons cost that little?

 

[dq409]

Looks like about $200 vs $320 for forged.

??????? And for $120 more you get a way better piston !!!
I don`t know,,,, I think I`d spend the extra cash,,,,,
dq

 

[Tic's60]

Ok I'll throw in on this

The LS7's specifications are significant for a production engine:

500 horsepower @ 6200 rpm
475 lb.-ft. of torque @ 4800 rpm
7000-rpm redline
Unique engine block with larger 104.8-mm (4.125-inch) bores and pressed-in cylinder liners
Forged steel crankshaft with 101.6-mm (4-inch) stroke
Titanium connecting rods
Cast aluminum flat-top pistons <------ Please note Cast Pistons are used
Racing-derived CNC-ported aluminum cylinder heads with titanium intake valves and sodium-filled exhaust valves
Dry-sump oiling system
11.0:1 compression ratio
Camshaft with 15-mm (.591-inch) lift
Hydroformed exhaust headers with unique "quad flow" collector flanges.

This should be fun

 

[models916]

Hypereutectic is better than just cast aluminum

Hypereutectic pistons are considered safe to use without power adders. Street engine? Not a problem. KB heat treats their pistons different than others, hence the higher cost over Federal Mogul. Oh, and don't forget to gap that second ring larger than the top.

 

[1958 delivery]

Hypereutectic pistons are considered safe to use without power adders. Street engine? Not a problem. KB heat treats their pistons different than others, hence the higher cost over Federal Mogul. Oh, and don't forget to gap that second ring larger than the top.

This brings me back to square one. I've seen a lot of street engines break the upper ridge. Yes, probably got into detonation. I would pay the extra $120 for forged, unless it's an absolute grocery getter.
I have an absolute stock original 67 El Co, 327 4spd. I built it with cast pistons, cast iron intake, quadrajet etc.
My 57 Bel Air 350, has forged pistons, steel crank, alum heads, etc
Two different animals for my driving style.
I consider Hyper pistons as glorified over priced cast pistons. Just my humble opinion.

 

[Bungy]

I'll toss in my vote for what it's worth. (yah I know, not much) I've used the Hypereutectic pistons (Speed Pro) in two small blocks with both of them being abused very hard. One ran for 6 years before blowing a head gasket. The other is still in use today (must have about 75,000 miles on it) Never had a problem with the pistons in either. I say use em. Another benefit besides cost is you can run tighter clearances with them and won't have the rattle at start up as with the forged with the wide clearances.

 

[oldskydog]

Hypereutectic pistons are considered safe to use without power adders. Street engine? Not a problem. KB heat treats their pistons different than others, hence the higher cost over Federal Mogul. Oh, and don't forget to gap that second ring larger than the top.

Models,
The instructions for the KB pistons call for an increased gap on the top ring. They say it's higher up on the piston than what we are used to and with the tighter clearances it gets hotter on the top ring and needs more clearance for expansion. When I told my engine builder he said he had never heard of that. Maybe that's why the tops break off if the the machine shops guys don't give the top ring more clearance.:eek:

 

[chevymusclecars]

Cecil

I have no experience with the pistons but question why if you have a 67 Nova with the original block why would you even take the chance? All of my engines are high performance big blocks or 409s and I would not consider anything other than a forged piston and crank in them. An original engine block is not replaceable.

Just my opinion.

Bill

 

[oldskydog]

Cecil

I have no experience with the pistons but question why if you have a 67 Nova with the original block why would you even take the chance? All of my engines are high performance big blocks or 409s and I would not consider anything other than a forged piston and crank in them. An original engine block is not replaceable.

Just my opinion.

Bill

Bill,
Without a doubt if it was the original 362 block I would go the extra expense but my block is a CE warranty replacement Chevy II 327 block casting 3959538 with a casting date of Jan. 69. It was an L-79 replacement with the high compression pistons and 350 hp cam although it was only rated at 325 hp in 67. It's just for fun since it would never be correct as an L-79 car.