big block 400

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moparguy440

moparguy440

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ok here the deal I have a 75 big block 400 low miles I was going to stroke it to a 470 and drop it in my 70 dart but after getting it all apart the bearing all look good rod and mains,,so im thinking of building a beefy 400 taking it .040 h beam rods after market steel crank and aluminum heads a good forged piston 10:5 or above and huges .576 .584 cam,heres the ? has anyone ran or running the aftermarket aluminum heads imported from china there 500 cheaper than brock heads and are saying and showing same specs hate to spend 900 for a junk import head
 
moparguy440 said:
ok here the deal I have a 75 big block 400 low miles I was going to stroke it to a 470 and drop it in my 70 dart but after getting it all apart the bearing all look good rod and mains,,so im thinking of building a beefy 400 taking it .040 h beam rods after market steel crank and aluminum heads a good forged piston 10:5 or above and huges .576 .584 cam,heres the ? has anyone ran or running the aftermarket aluminum heads imported from china there 500 cheaper than brock heads and are saying and showing same specs hate to spend 900 for a junk import head
Click to expand...

Heck, my .02 would be if your spending the monies to buy H-beam rods and an aftermarket steel crank, why not just get a stroker kit!

However the 10.5 compression would wake the 400 up with the right other components.
 
Which heads are you referring to? Sometimes depending on final machining,metallurgy,design they are O.K and sometimes not...I think the 440 source heads might be fine.
 
What are your goals? If you are looking for high hp numbers and low e.t.s and you want to spend that much money to get H beams and custom pistons, might as well drop the extra to stroke it...even a 3.75" stroke will net you 450 cubes.

If you just want a cruiser, stay 400. Built well it'll still make 425-450 with those aluminum stealth heads you mentioned...

Really comes down to how much you can spend
 
The only reason I'd use Stealths is because the customer want's a factory looking head after it's painted. You will put the same money into RPMs as Stealths but IMO the castings are more consistent on the RPMs. Both make similar power and have similar potential although I'd ultimately give the knod to the RPMs for the spark plug location. Brandon just stole the RPM ports and put them into a stock type head casting so the plugs are straight.
 
Aren't the Stealth's combustion chambers 4 cc's smaller? That seems to be overlooked in many of the comparison discussions. Slightly higher compression ratio could cause some problems depending upon the set-up.
 
They are indeed advertised as 80cc nominal chamber volume, but depending on the piston choices and deck clearance, that 4cc shouldn't be a make or break for compression in most apps.

Let's assume for the moment, he runs a .040" over 400, with flat top pistons w/6cc valve reliefs (typical) 0.008" under the deck, with a .038"x4.4" gasket...with an 84cc head, he's looking ~10.1:1, with an 80cc chamber closer to ~10.5:1. In either case, you're going to have to be scrupulous with your induction, cam choice, stall, gear, etc. especially if your local fuel blends suck.

Assuming wise choices with parts and tuning, it *shouldn't* be a big issue.
 
desmo900 said:
Good information. What would his quench be with that set-up?
Click to expand...
I just want to thank everyone for the imfo I do plain on running the thicker head gaskets and if the 93 octane is not enough we do have the e85 fuel which Im thinking is around 104 or higher level octane but im thinking with aluminum heads water pump and intake along with radiator I should have no heat issues with it.and yes I was plaining on decking the block .020 and running the trw flat tops
 
desmo900 said:
Good information. What would his quench be with that set-up?
Click to expand...

If you read my description, it'll give you quench...

0.008" in the hole +
.038" head gasket = .046" by the math quench. The other way would be to mock it up and take a squish measurement from some play doh.
 
moparguy440 said:
I just want to thank everyone for the imfo I do plain on running the thicker head gaskets and if the 93 octane is not enough we do have the e85 fuel which Im thinking is around 104 or higher level octane but im thinking with aluminum heads water pump and intake along with radiator I should have no heat issues with it.and yes I was plaining on decking the block .020 and running the trw flat tops
Click to expand...

Be careful, there's another thread going on right now about good quench on a high compression engine and how it's wreaking havoc on detonation. If you're going to buy aftermarket pistons you might be able to find a set with a mild dish to keep the compression down and still run a tight gasket and keep the pistons at the top of the deck for good quench.

You may ask, "why run a dish at the top of the deck? Won't that have the same effect if I run flattop pistons with a thick gasket?"

Not necessarily. Even dish pistons still have an edge that runs close to the deck, and will create quench...

If you're going to the trouble of buying good pistons (which oddly enough are more available than 383 slugs) buy some to suit your uses
 
another option is run to the deck flattops with good sized reliefs, close quench, and work/blend the chamber to a little larger size...
 
txstang84 said:
If you read my description, it'll give you quench...

0.008" in the hole +
.038" head gasket = .046" by the math quench. The other way would be to mock it up and take a squish measurement from some play doh.
Click to expand...

I figured as much but wanted to confirm. Thank you.
 
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