ironhorse583

iTrader: (5)

many say it isnt worth the money..any1 have any real world data..going from stock 243s to ported 243s has to b worth power..

so u take an ls2 with stock head and intake running 15lbs of bosst making say 700rwhp...

now take the same ls2 add ported heads and a fast 102...the added airflow drops boost say 3psi..u pulley down to make up that 3 psi..how much power is it worth.?

ironhorse583

iTrader: (5)

here is something i came across...do u think it holds true.?

generally understood that .257 Flow_Factor is a pretty good measure
of HP expected per Cylinder for certain Flow gain
in N.A. engines

15 psi Boost Pressure has a potential pressure differential of =
approx 412.0 inches of water

( 412 / 28 ) ^ .5 = 3.837

3.837 * 20 CFM = 76.75 CFM increase @ 15 psi Boost

76.75 CFM times .257 * 8 Cylinders = 157.8 Potential HP gains
.....so subtracting various pumping + heat losses, etc.
gaining around at least double Intake Flow gains
which should easily be approx 82+ HP potential

The Alchemist

iTrader: (19)

I would think that more gains could be seen by getting the exhaust to flow better since you have 15psi (the example used) pushing air into the cylinder, you need help getting the spent air out of the cylinder and exhaust.

HCI2000SS

iTrader: (2)

The way I look at it is like this: Unless I was to forge the motor (and other necessary components) i'd just leave the heads alone. Any blower will easily max out the stock internals capabilities even with the stock HCI, so why upgrade the heads unless you plan on beefing up the internals at the same time. Just my opinion

RonSSNova

iTrader: (3)

If ported heads add power, w/o the added stress of more boost, isn't that a good thing?
I ported my 799's. it just made sense to me.

ironhorse583

iTrader: (5)

lets assume the car and motor are built to handle 30psi. ronssnova makes a good point..but how much does the porting help.? Alchemist i thought the same thing till i started researching the top fuelers..here is some info...

Top Fuel Dragster - Doug Kalitta - { High Wing DownForce model }
April, Houston, Texas 10 Feet Elevation { NHRA specs }
30.04 Sea-Level Corr.Barometer, 66 deg.F, 45 % Rh, 91 F Track surface

60 Ft= .847
330 Ft= 2.150
660 Ft= 3.058 - 279.04 MPH
1000 Ft= 3.822
1320 Ft= 4.486 - 333.91 MPH

2250 Lbs. 496 CID 4.187 Bore x 4.500 Stroke

Peak HP= 7933 @ 6715 RPM Peak TQ=6205 { 8550 RPM limit }

6.8:1 Compression Ratio , 2.400 Intake 1.940 Exhaust valves
39.3 % overdrive on Blower
62 deg BTDC at Starting Line & 58 BTDC at Finish Line


1.940 / 2.400 = .80833 E/I Valve Ratio

2.020 SBC Chevy Intake Valve = 1.632 exh Valve at that same
Top Fuel Supercharger application

the Power is on the Intake side !

Blown06

iTrader: (32)

Thats a horrible example to use..........fuel cars bring there own air to the game via the "fuel". Thats why you see such a bias.

The Alchemist

iTrader: (19)

Also, look at the exhaust on them. They are 2"+ primaries zoomies. Not exactly worrying much about exhaust velocity when they have no merge collectors, no mufflers, and the total length of the exhaust is like 3'.

ironhorse583

iTrader: (5)

both very good points...so back to the question..if u port the heads for an NA build and pick up say 25hp would that turn into 50hp when u add 15lbs of boost.?

ironhorse583

iTrader: (5)

good info in here on ported head results....

https://ls1tech.com/forums/dynamomet...e-800rwhp.html