Couple 400 upgrade questions

[jdscofield]

Hey guys,

Spring is around the corner so thoughts of "what to upgrade this year" are sneaking into my head.  Currently, I have a 400 bored .30 over, hypereutectic flat top pistons, eddy performer rpm intake, Holley 750 dp, long tube headers, flow masters, 727 with shift kit, and suregrip with 3:55's, and a turd cam ( camshaft is tender subject, needs to be swapped).

My plans this summer:

Firecore distributor, rev-n-ator
Whiplash cam

Some thoughts floating in my head:  engine still has low compression.  Could do 915 closed chamber heads, but the 452's flow better.  So, what about using 440 pistons with 400 rods.  If I had stock bore 400 pistons, I believe I would need .20 440 pistons.  Supposedly, it would raise my compression to 9:1.  If I were to swap out the .30 400 pistons with 440 pistons, would I then need .60 440 pistons? Would my compression be higher than 9:1 because the block is bored .30 over?  Would I need to do anything to the heads or could I leave them stock?  If using 440 pistons is even possible, can I use the 400 rods and bearings?  Ultimately, will this raise compression and create significant hp?

Also, planning on installing 2400 rpm stall.  Any recommendations?  Since the 400 crank is externally balanced, do I have to add weights to the converter, or would it come from the manufacturer ready to install.

Very interested in hearing your thoughts, advice, and experiences

[c00nhunterjoe]

Wht part number pjstons are in it.

[jdscofield]

Not sure.  To make a long story short, I had recently moved to a new state and needed my engine rebuilt. I was living in a apartment complex and couldn't rebuild it myself.  Even got reprimanded by apartment management for changing plug wires on property.  Anyways, shop owner and I discuss what I wanted done.  Zero deck block, bore .30 over, forged domed pistons, camshaft, compression ratio goals, etc.  picked up car, only secretary was at work.  Paperwork was vague.  Took shop owner almost 5 months to return my calls regarding specs.  Would never give me anything on paper.  Only description on paper I did receive says long block.  I stuck a camera down my cylinder, I do have flat top .30 pistons.  I am assuming they are stock height and just bored .30.  Also assuming block was not zero decked, heads and intake were not shaved to reach desired compression, and camshaft was not the one I wanted

[Nacho-RT74]

not too many options for 400s...

if you got Hypereutectic pistons mostly sure you have KB240s pistons in it. Practically only option for 400s, aside get custom forged setups. On blue printed blocks they sit 0.020" below the deck ( per specs ). But if block was not decked to blue printed specs, maybe they can be on 0.030-0.040 below the deck.

The option for compression upgrades more than KB240 gives as far I know are ( still being a 400 ):

-Custom pistons

-Closed chamber heads

-a combination of above

If you don't have KB240s on block, they are a really good option out of the box, even better if you make Zero deck and closed heads, getting quench on headgasket thickness... or getting block blue printed, making to sit pistons at 0.020" below the deck and using metallic headgaskets. Then find a camshaft that suit your desires and match the TC ( yes, with counterweights )

if you want to change to forged crank, get a 383 forged one, allong with Balance dampener and forget about TC counterweight

THAT was to be my own project long time ago, untill I found allmost for free a 440 crank then made the stroker ( basic )


From there, the next options are Stroke it, using:

-Modified Stock 440 crank ( just cutting counterweights and mains ), then use 400 or 440 rods then get Hypereutectic or forged pistons accordingly to the rods selected

-Same as above but cutting offset the rod journals and setting rods and pistons accordingly ( options are there ).

-Aftermarket cranks being sold around on kits allong with rods and pistons

Cut block to zero deck on stock pistons would mean cut maybe 0.15-0.20". Too much.

Allong with everything of these... bigger valves and porting job

[jdscofield]

Hey Nacho, I was hoping you would chime in.  So you think the 440 piston idea won't work?  I was laying on the couch last night thinking about different ways to raise compression in that motor.  I thought maybe it would work because the 440 pistons are a little taller, that I would just have to match the width.  I'm not sure if the block was zero decked or not.  Between the way my paperwork reads ( long block ) and his pausing to look through notes to answer questions, I am starting to think he ordered a remanufactured block with a .30 bore.  However, now that I'm thinking of it, I'm pretty sure he sent it to the machine shop like he said he did.  The heads are e definitely the ones I had before because I had snapped two valve cover bolts and had to use helicoils.  I also remember him calling me because something with the lower portion of the distributor was messed up and was waiting for the part to come from Detroit and also informing me that the block was already bored.10 over.  So, should I assume that if he sent the block to the machine shop to be tested and bored, then it was probably zero decked?  He did tell me my compression was 8.75:1 and that the reason the pistons were hyperutectic was. Ecause he couldn't find aftermarket forged pistons.  What do you think?

[Nacho-RT74]

440 pistons on a 400?

Ok let's see. Here is a list of sealed power piston stock replacements and specs. Check the CH if is posible

http://www.campbellenterprises.com/mopar_sealed_power_cast_pistons.htm

KB240 pistons CH is around 1.908" and per manufacturer specs on a blue printed block sits 0.020" below the deck. That means you can fit a 1.928" CH piston into a blue printed 400 block to get zero deck

Making the maths it seems stock later 440s replacements low compression pistons will fit 0.016" below the deck. It seems posible. Need to check your deck height first though.

But aren't these also longer skirts and heavier?


I'm definitely NOT the guy to talk about this, just thinking out loud.

[Nacho-RT74]

KB240s got valve reliefs, where stock not so you have to be sure about cam lift

Now, this is comparing with stock replacements to be a cheaper. If you think on another 440 replacement performance pistons, then is a no brainer, KB240 are the ones out of the box on a same price rate with others

This is just IMHO