[Formulajones]

I don't use hypers in anything. Never had a noisy forged piston either so not sure what others have going on with that deal

[ponchjoe]

Thanks, KBd would be a last resort for me. I’ll probably just go heavy Speed Pro

Originally Posted by chiphead

You guys still think Hyper pistons are a viable alternative? What about resistance to detonation and ring butting? Hyper pistons are high silicon content. They are dimensionally stable, but are brittle. Heavy detonation can crack them.
Some designs (particularly the KB hypers) tend to put a lot of heat in the top ring. In high power, nitrous or boosted engines, they tend to butt the top ring and tear the top of the piston off. They also cannot have dished milled in the top to lower compression. For a low compression, lesser than 400 HP builds, they would be an option. But if you get the bug for more HP, the hyper pistons quickly become a limiting factor to power production.

I used a set of Ross 2618 pistons in a long rod 400 nitrous street/strip motor. It ran for 10 years and about 15K miles. My only complaint was the piston slap when cold. Upon teardown, the pistons were good, even though the rings and bearings showed signs of being unhappy due to years of being run hard. The looser bore clearance makes some noise when cold and can shorten ring life. At least in 2004, the Ross pistons had limited options for customization. I sold those used Ross pistons to somebody here, they were still perfectly good.

Since I like to make the max power on pump gas and use nitrous, I have to use good pistons and rings. That 434 got the Autotec pistons and a $350 set of AP stainless LS style rings, torque plate honed, 6.8 BBC rods, the whole burrito. For a cruiser, the only pistons I would NEVER use would be a hypereutectic or the 8-eyebrow cast monster. Just be sure to consider the compression, camshaft choice, RPM range, gearing and risk of detonation with less expensive pistons and ring packs.

[AG]

Icon forged if one will fit your desired CR. Otherwise it's custom piston and choose your favorite manufacturer, doesn't matter who that is since they are all over $1100 with rings (Ross, DSS etc).

[chiphead]

Originally Posted by ponchjoe

Thanks, KBd would be a last resort for me. I’ll probably just go heavy Speed Pro

That should be fine. A TRW piston with moly top ring, ductile iron 2nd and standard tension oil rings will be fine. I assume aftermarket 6.625 rods with press fit pin?

The next concern is compression. What heads are you using to get 9:1?

['ol Pinion head]

AutoTec 4032 alloys here in one build (slight domes, metric ring pack). Bought em from Shanon's 7 years ago when they were a smokin deal. Next set will be flattop AutoTecs from Paul K, once Don @ DCI has the mid 80cc chamber round port heads available.

[Jay S]

Originally Posted by AG

Icon forged if one will fit your desired CR. Otherwise it's custom piston and choose your favorite manufacturer, doesn't matter who that is since they are all over $1100 with rings (Ross, DSS etc).

The Icon IC890 have a decent quech, DSS and Ross for a 400 you have to deck the block to get a good quench. The DSS and Ross from Butler also all went to reversible pistons with the intake sized relief on both valves. They loose some compression against an icon. The IC890 icon for a street and strip 400 is a very nice piston.

[rohrt]

To me, even with a buget street build I would spend the money on the best short block build that you can and cheap out elsewhere. Meaning foged rods and the best bang for the buck piston. The short block is one place you cant easily go back and redo.
My researh has found Icon and Autotec hard to beat and way better then the old TRW as already stated.

[grivera]

Originally Posted by AG

Icon forged if one will fit your desired CR. Otherwise it's custom piston and choose your favorite manufacturer, doesn't matter who that is since they are all over $1100 with rings (Ross, DSS etc).

These are the ones I meant by KB forged

[ponchjoe]

Originally Posted by chiphead

That should be fine. A TRW piston with moly top ring, ductile iron 2nd and standard tension oil rings will be fine. I assume aftermarket 6.625 rods with press fit pin?

The next concern is compression. What heads are you using to get 9:1?

Ported 7k3, zero decked

[SD455DJ]

Originally Posted by Jay S

The Icon IC890 have a decent quech, DSS and Ross for a 400 you have to deck the block to get a good quench. The DSS and Ross from Butler also all went to reversible pistons with the intake sized relief on both valves. They loose some compression against an icon. The IC890 icon for a street and strip 400 is a very nice piston.

I agree!

Dennis

[Rar_421]

Just looked at a set of srp pistons, any reason they are designed with a 1.690 compression height?
Anyone using them,how much was taken off the block to get a zero deck?

[tooski]

Originally Posted by JLMounce

. The SpeedPro's may be around $400.00, but you're going to need to add rings to that, so the prices can start to narrow a little bit.

I don't think the SpeedPro's are full floating. So also added would be the machine shop cost to put them on the rods.

[Kenth]

No love for the KB hypereutectic pistons? Aside from the needed larger gap on upper ring, which may be missed during assembly how bad can they be in a street engine?
Anyone used and broke them and why did they brake?
I have a set in my 421 with 4.16" bore, so far so good.

[PAUL K]

Originally Posted by Kenth

No love for the KB hypereutectic pistons? Aside from the needed larger gap on upper ring, which may be missed during assembly how bad can they be in a street engine?
Anyone used and broke them and why did they brake?
I have a set in my 421 with 4.16" bore, so far so good.

Set up properly the KB Hypereutectic pistons work well. They run quiet, help the rings do their job due to the tight running clearance and keep heat in the combustion area..... Their down fall is they're detention intolerant and when they break you have catastrophic results.

[dataway]

I'm not an engine builder, but I built my current engine using the Speed Pro pistons. I consider the pressed in pin a major disadvantage. Just another thing a machine shop can mess up (they did mess up one of mine that had to be replaced).

The weight and rings were not a big factor for my street engine, but the hassle of worrying about a shop over heating the rods, or tweaking the pistons when pressing the pins isn't something I'd want to do again.

[Joe-Touring]

I bought a blown up 455 a couple years back. Had KB Hypereutectic pistons in it. Not sure of the whole story, that engine was a disaster, but to the point: top ring touched itself and popped off a chunk of the piston crown.

Happened to be a in a cylinder that already had a replacement sleeve. Cracked that sleeve. So now the block needs to be re-resleeved :/

[Kenth]

Hardly the pistons fault if the mechanic is ignorant.

[Dragncar]

Originally Posted by Joe-Touring

I bought a blown up 455 a couple years back. Had KB Hypereutectic pistons in it. Not sure of the whole story, that engine was a disaster, but to the point: top ring touched itself and popped off a chunk of the piston crown.

Happened to be a in a cylinder that already had a replacement sleeve. Cracked that sleeve. So now the block needs to be re-resleeved :/

The guy did not follow KBs instructions.

[Cliff R]

I still remember being in the pits at Norwalk about 20 years ago and a guy pitted next to us "hit" his new 455 build with a shot of nitrous with disasterous results. He tore the engine down at the track since he was stuck there for the long weekend anyhow. Most of his new KB HT pistons were missing from the bores and piled up in the oil pan. They shattered like glass and left the rods and pins moving up and down in the bores void of any pistons on them.....NO THANKS!

I know that's an extreme scenario but it tells us that they have an elastic limit far below what you'd see from a decent forging, even the WAY too heavy TRW/Speed Pro forgings. Not a fan of those either because every set I've ran into ends up WAY to far down in the holes at TDC when I mocked them up required too much to be machined from the block to establish Zero Deck.

Anyhow, I've used Ross which are nice, and ICON, KB forgings. Since all my engines get forged rods and most will have the full floating option they fit the bill nicely. The modern alloys also allow for tight fitting compared to antiquated forgings from long ago. With a torque plate for final honing I set them at .002" here and have never had a single issue with that deal.

Even with all that said IF they made a nice flat top cast piston, even pressed pin I'd use them. Nearly all of my SBC builds get flat top cast pistons and they are fit really tight for minimal "rocking" in the bores, good ring seal and long life expectancy. The cast piston options for the 400's are absolutely pure bovine excrement and always have been. I still remember mocking up an engine I was hired to assemble decades ago using those pistons. They were WAY down in the holes at TDC and already taking over 15cc out of the squish area like using a dished piston. Team that up with a 4X or 6X-8 head in a 400 build and you'll have about as much compression as a Briggs and Stratton lawn mower engine, and left wondering why it doesn't idle or run for chit once placed in service......

[Formulajones]

Originally Posted by ponchjoe

Thanks, KBd would be a last resort for me. I’ll probably just go heavy Speed Pro

It's not a bad choice, just be aware as Cliff mentions you'll have to shave a bit off the deck to get them at or near zero. I've used these pistons before in builds some 25+ years ago before we had all the nice choices we have now. Those engines are still together today, quiet as a mouse and running fine, but as mentioned, the blocks needed decked to get them up to the top.

That's not necessarily a bad thing as every single engine I've ever touched needs decked anyway simply because they are so far out of spec, and Pontiac is one of the worst with that deal. You'll find them lop sided many times having to take as much as .007-.0010 more material off one end compared to the other end to get them square. So it's not like it's the end of the world using the speed pros anyway. Probably my bigger gripe with them is the large tractor ring package they come with. That's pretty antiquated these days as smaller ring packs have proven themselves to be a better deal all around with better sealing abilities, lighter weight, less drag, all equals more HP.

The price differences aren't really enough to even consider a decision maker in my opinion anyway, I'd just go with a nice modern forged full floating deal with a small ring package and call it a day.