[mike4814]

Ok heres the combo:
406 small block
10:5 cr
280H comp magnum
roller tip rockers
demon carb
weind dual plane intake
hooker header
2 chamber flowmaster
stock heads 194 * for now open to sugestions on what to run

what kind of power do you think i'll make the way it sits? and after a head swap to a nice free flowing set of heads? Thanks

 

[Motorhead62]

Mike,

That is about a 375 HP combo. Bolting on heads will add another 50 -100 depedning on which head. Are you sure you have a 10.5-1 cr?

 

[mike4814]

if i rememeber correctly the pistons are flat top keith blacks. I believe the machine shop said cr would be around 10-10.5:1. I know the block wasnt decked and the heads were not milled.

 

[Bill70]

I built a 8.5:1 406 with Comp 268H cam, Performer intake and Hooker headers. It was less than spectacular. I later took the heads off and had 2.02/1.60 valves installed and it made a huge difference. Power was up where I expected it to be. IMO, don't bother with small valve heads on a 400. You would be leaving a lot of hp on the table.

 

[Motorhead62]

Mike,

Then you are right in there for a set of heads like the Performer RPM.

 

[DZAUTO]

I cannot count the number of times that I have recommended using high flowing aftermarket heads on a healthy SB400. It almost seems that some people just do not relate the displacement of a small block to that of a big block.
But, no matter how you slice it 400+ cubic inches is 400+ cubic inches, regardless of whether it is a SB or BB!!!!!!!!!!!!!!!! Consequently, it needs to breathe!!!!!!!!!!!! You wouldn't put mickymouse port/valves in a BB 396-427, so why do it on a SB?????????????? Makes no sense to me.
If you want max output on a SB400+, you really need something like World or Dart heads with 210-220cc ports and 2.05 or 2.08 intake valves! And guess what? YOU STILL END UP WITH THE BIGGEST VALVES THAT ARE STILL SMALLER VALVES IN A SB HEAD THAN THE SMALLEST VALVES THAT COME STOCK IN A BB HEAD!!!!!!!!!!!
Nominally, about the BIGGEST intake valve for a SB head is a 2.08, and the SMALLEST intake valve in a BB head is 2.19. The BIGGEST exhaust valve used in a SB head is 1.6, but yet the SMALLEST ex valve in a BB head is 1.72. Big block heads are well known for their superior breathing ability. Again, 400+ inches is 400+ inches, and to extract max performance from 400+ inches, it needs to be able to breathe! So, give your SB400 a head start!