400 HiPo pistons to stock specs engine

[Nacho-RT74]

Where to find HiPo pistons to 400 engine using stock rods and everything... a friend of mine wants to find some pistons with better comnpression than stock ones. Untill now I only have found 400 pistons to stroker engines and 400 with same or similar stock specs.

He wishes 10:1 CR, but anything better than stock 8.2:1 will be Nice.

[firefighter3931]

Those will have to be custom made. Diamond racing can make them and they're not much more $$ than an "off the shelf" piston. They will also be a little lighter than stock.


Ron

[Challenger340]

KB240 made by Silvolite/Keith Black, might be an option to investigate. 

[Chryco Psycho]

personally I will not use KB Hyper / cast pistons

[chargerbr549]

Another option might be to use the low compression piston for the 440, I have read about people doing that but I have never done it myself. I think the factory 440 low compression piston is about .100 taller than the stock 400 piston so you should be in the neighborhood of 10 to 1, just remember that the 400 has a stock bore of 4.340 and the 440's is 4.320

[Challenger340]

personally I will not use KB Hyper / cast pistons

Not Even for Non-Nitrous, Non- Blower applications, just street, "pump gas" style engines ?

How Come  Chryco ?

[AKcharger]

Another option might be to use the low compression piston for the 440, I have read about people doing that but I have never done it myself. I think the factory 440 low compression piston is about .100 taller than the stock 400 piston so you should be in the neighborhood of 10 to 1, just remember that the 400 has a stock bore of 4.340 and the 440's is 4.320

So you'd have to sleeve the cylinders? how could you make that work?

[chargerbr549]

A 440 piston .040 oversize would be .020 oversize in a 400 block and a 440 piston .060 oversize would be .040 oversize in a 400 block so you shouldn't have to sleeve it all.

[Nacho-RT74]

Nice stuff you told me about low compression 440 pistons ... we will analize. I know about the 020 difference, but didn't know about the height. I guess you talk about post 72s 440s. Pin is at the same height too ?

AK, sleeve the engine is not a big deal... in fact engine is already sleeved. Mine is also sleeved to standart bore.

Chryco... I have got nice coments about KB240 pistons for street use from moparguy01 and I think RD is on them... what's the deal about what you think.

Challenger340 is right, is just street gas 95 oct use...

[Challenger340]

I believe the KB 240 Piston will be substantially lighter than a stock low-pop 440 Piston as well, easier to balance the engine, to stock, as it's made for THAT 400 application.

That, and it will be made for a "400", in whatever oversize you desire.

Some "PRO's" of the KB 240;

Cheaper to buy than Forged.

Utilizes an "accumulator chamber" ringpack design, thats the big "space" between the top & second ring lands, provides a volume, so pressure doesn't build up between the compression rings. Nice RPM feature, on a street engine.

Hypereutectic alloy; provides extremely good thermal stability. Doesn't change as much dimensionally from cold to operating temp. as other pistons, hence, you can run tight Piston/wall clearances ( so KB says).

Very light weights for comparable mass of alloy used.

Huge Flycuts; you can pretty much run any camshaft/any lift, without Piston to Valve issues.

CON's of the KB 240;

Must run "specific" top ring end gaps, read LOTS ! Alloy characteristic and conductivity, transfers excessive heat into top ring, which may "Butt-ends" if proper top ring gap(supplied by KB), is not adhered to. FILE THE TOP RING GAP !

Hypereutectic; high silicon content alloy;
The very thing, "silicon content", that makes it hard, strong, and thermally stable, also unfortunately, makes it "brittle" and susceptible to Cracks when exposed to high shock loads.
Example; severe "detonation", as can be experienced with Nitrous or Blower applications, a high frequency dynamic factor. Think "wine glass" and the Opera singer ! Not a very forgiving alloy in those applications. Softer, regular Cast Pistons, are actually more forgiving in those app's, but too weak otherwise, so they fail too.

Must use a Torque-Plate on the block when fitting Pistons, that, or add .001" to KB recomended clrc. Should always use a T-plate anyways, on ANY Piston fit job.



Personally, I have no problem with the KB Hypereutectics in a Non-Nitrous, Non-Blower/boost, type "Street" H.P. application. I've even machined/built a few "bracket-bashers", running mid 11's with them, absolutely no problems for years now.

Hope the above info helps your decision. By no means is it complete, but, just a few considerations.

Personal decision, Your Call

[Steve P.]

I have a set in a motor I am putting in my Coronet. (They were in the motor when I bought it). I had a local engine shop go through and check everything. Right off the bat they found problems with the build. (From what I have heard, the original machine shop was top of the line). Well, they screwed up on this one. Too much to tell.

Most of the machine shops around here LIKE the KBs. Of course when they blow up due to PING or whatever else, they get your money again for the next build.. Haha....   

I'm going to try them in this motor, but if I had to buy a new set of pistons they would be forged...

(NOTE): I live in rainy Florida and it is not uncommon to end up with some water from the gas station..

[Nacho-RT74]

Huge Flycuts; you can pretty much run any camshaft/any lift, without Piston to Valve issues.

Good because probably will be stock 74/later Magnum one. ( One low miles used I have since gas pump cam and rod on his engine got a REALLY HARD damage. Gas pump rod will be make by a machine shop starting from a NOS one I have )

CON's of the KB 240;

Must run "specific" top ring end gaps, read LOTS ! Alloy characteristic and conductivity, transfers excessive heat into top ring, which may "Butt-ends" if proper top ring gap(supplied by KB), is not adhered to. FILE THE TOP RING GAP !

didn't get it completelly, but Moparguy01 told me something about that

Must use a Torque-Plate on the block when fitting Pistons, that, or add .001" to KB recomended clrc. Should always use a T-plate anyways, on ANY Piston fit job.

Sorry didn't get either... but consider I'm not a mechanic or maybe is a technical language issue... will read with attention later.

[Challenger340]

Nacho-RT74

If you use the KB Pistons, it's best that the shop doing the boring/honing, has a Torque-Plate to install on the Block, when machining.

[Chryco Psycho]

the $200-300 saved using the cast piston barely pays for the gasket set to rebuild the engine , + if you have forged pistons in the engine & want more out of it later you do not need to rebuild again
this is a no brainer

[AKcharger]

A 440 piston .040 oversize would be .020 oversize in a 400 block and a 440 piston .060 oversize would be .040 oversize in a 400 block so you shouldn't have to sleeve it all.

Brilliant!

This is a great thread...I'll have the same issue in May when I rebuilt my wife's 400...need better compression never thought of 440 pistons

[firefighter3931]

A 440 piston .040 oversize would be .020 oversize in a 400 block and a 440 piston .060 oversize would be .040 oversize in a 400 block so you shouldn't have to sleeve it all.

The 440 and 400 use 2 different length rods so the compression height might become an issue when trying to mix and match stuff. Honestly, for a few hundred dollars extra i don't see any reason to build a frankenstein shortblock when good parts are out there. I'm in agreement with Chryco, build it with a forged piston and it'll take a lot of abuse. 


Ron

[Challenger_7]

Hi Guys, I'm new here, this is my forst post
For what its worth, visit www.440source.com, recommended to me by a friend from this site. It might serve your purpose.

[Chryco Psycho]

the low compression Speed Pro 440 piston is actually short enough to fit a 400 block & yeild good compression , I have done this before

[firefighter3931]

the low compression Speed Pro 440 piston is actually short enough to fit a 400 block & yeild good compression , I have done this before

Interesting 

Wouldn't this create some balance issues though ? 



Ron

[Chryco Psycho]

778 gms for the 400 piston
802 gms for the 440 piston

[firefighter3931]

778 gms for the 400 piston
802 gms for the 440 piston

Thanks, that's what i figured. I suppose any non stock piston is gonna require a balance job anyway....



Ron

[Chryco Psycho]

it should be balanced anyway & it is not far off

[Challenger340]

the low compression Speed Pro 440 piston is actually short enough to fit a 400 block & yeild good compression , I have done this before

What 440 Speed Pro Piston, is actually short enough to fit ?  Can you please clarify ?

Is it the 424P ? "CAST" rebuilder Piston @ 1.912" Comp. Dist, another CAST rebuilder Piston, or, the L2266F Forged Piston @ 1.99" comp. distance. ?

Apologies, I couldn't find any others.

Which one did you use ?  How was the Piston Pinboss to Counterweight clearance ? Was it an issue ?

Any info would be greatly appreciated, Thanks.

[Chryco Psycho]

L2388F .155 below deck in a 440 block no valve reliefs

[Challenger340]

I could not find a Speed Pro part number L2388F, as a valid Part #, could you recheck Part number , Thanks.

I tried online here at; http://www.21cgt.com/FMWebCatalog/default.htm