Cylinder head swap

lwarrior1016 · Dec 8, 2015

OLD H2S said:
Can the JBA PI shorty headers fit a NPI head? How about with some work?

PI and NPI accept the same exhaust manifolds.

JerZeyStangz · Dec 8, 2015

ttocs said:
I replaced my BBK with JBA and was amazed in the difference. Better welding/fit thicker flange just all around top notch product.

Looks like superior product in the pictures compared to other brands. You get what you pay for!

lwarrior1016 said:
PI and NPI accept the same exhaust manifolds.

That awesome. Noted.

ttocs · Dec 8, 2015

I never thought there could be that much of a difference in headers since its all just plumbing really but taking the old crusty bbks out and holding them both you could feel how much beefier the JBA was. And like they said above looking at the welding it was just so much cleaner. I sent them off to nitroplate and had them coated to hopefully help them last and keep temps down.

JerZeyStangz · Dec 8, 2015

[video=youtube;O1bXPNy1Yn4]https://www.youtube.com/watch?v=O1bXPNy1Yn4[/video]

This video really helps you narrow down what headers do what and the proper sizing...

96laseredcobra · Dec 8, 2015

I'm running Bbk shorties tuned length. And will be putting them on the pi heads in Feb.

sent while thinking of mods for my 4.6s using tapatalk

96blak54 · Dec 8, 2015

You haven't stated a pi swap in your build thread?

OLD H2S · Dec 9, 2015

Well I liked that video, BUT...while helpful we are comparing apples to oranges. A 4.6 motor flows 400 cfm at 5000 rpm, this is with the heads off and no restrictions obviously. You must pick the real world rpm you will be running at, road race, drag or street, makes a big difference in everything, but you know that. When you hit your red line are you shifting in a 10th of a second or running down the front stretch for 30 seconds?
A 427 Chevy flows 617 cfm at 5000 rpm and 772 at 6250 rpm, this is a lot more than our puny 281 cid can, we max out at 508 cfm at 6250 rpm. No need for big tube sizes, 508 divided by 8 cylinders is 63.5 cfm for each jug, not really much waste gas to get rid of, But it is very hot and expanding into the exhaust manifold at very high speed. Lots of design work to get it out, maybe scavenge the next cylinder, push a turbo ect.
I have had 3 Terminator motors and liked the stock Cobra manifolds the best, junk you say? They pull the same hp numbers as short tube headers, now I lost 30 hp at 6250 rpm to long tube headers but running a 3.27 rear gear the car was going so fast at 5000 rpm I never used the extra hp the long tubes made any way and they were a pain with the extra noise and fitting headaches. I killed 4 transmissions, having to fit around steering shafts, getting them off to remove the trans was killing me, I sold them to a burn out king and he loved them, his tire expense was nuts. To each his own...
Maybe I will chop up the stock flange and cut a Cobra set off and weld up a set of cast iron Cobras that fit a NPI head ????
Flame on guys..

JerZeyStangz · Dec 9, 2015

OLD H2S said:
Well I liked that video, BUT...while helpful we are comparing apples to oranges. A 4.6 motor flows 400 cfm at 5000 rpm, this is with the heads off and no restrictions obviously. You must pick the real world rpm you will be running at, road race, drag or street, makes a big difference in everything, but you know that. When you hit your red line are you shifting in a 10th of a second or running down the front stretch for 30 seconds?
A 427 Chevy flows 617 cfm at 5000 rpm and 772 at 6250 rpm, this is a lot more than our puny 281 cid can, we max out at 508 cfm at 6250 rpm. No need for big tube sizes, 508 divided by 8 cylinders is 63.5 cfm for each jug, not really much waste gas to get rid of, But it is very hot and expanding into the exhaust manifold at very high speed. Lots of design work to get it out, maybe scavenge the next cylinder, push a turbo ect.
I have had 3 Terminator motors and liked the stock Cobra manifolds the best, junk you say? They pull the same hp numbers as short tube headers, now I lost 30 hp at 6250 rpm to long tube headers but running a 3.27 rear gear the car was going so fast at 5000 rpm I never used the extra hp the long tubes made any way and they were a pain with the extra noise and fitting headaches. I killed 4 transmissions, having to fit around steering shafts, getting them off to remove the trans was killing me, I sold them to a burn out king and he loved them, his tire expense was nuts. To each his own...
Maybe I will chop up the stock flange and cut a Cobra set off and weld up a set of cast iron Cobras that fit a NPI head ????
Flame on guys..

I get what your saying but the 1996 Iron exhaust manifolds have to be even "punier" than a stock terminator manifolds by far. Ford had to have change the exhaust diameter to even get a decent performance from the terminator engine. I will be using TFS heads so I think the JBA's will be a good pair for me with Positive displacement blower.

Does the CFM of air change when there is blower on top of the motor as the manifold being pushed by given rpm?