Head flow rate effect to HP ratings?

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Hi guys,

I am having a stroked 496 BB on the engine stand and I am in the middle of choosing the heads for it. I already have stock 440Source heads that flow on intake [Email]290CFM@.600[/Email] valve lift, exhaust [Email]220CFM@.600[/Email] lift.

I just ran into CNC ported 440Source heads that flow a little better, intake [Email]315CFM@.600[/Email] lift, exhaust [Email]233CFM@.600[/Email] lift.

The cam I am going to use will give almost .600 lift on the valve with 1.6 rockers

The flow rate difference between these two heads is not a big one, on intakes 25CFM and exhausts 13 CFM. in percentages it's 8.5% and 6%.

By experience can you estimate how much the head flow increase will effect to the HP rating?

I know that exact numbers can't be given, but it would be nice to hear your experiences or real figures if you have had your engines dynoed after a head change.

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Hi guys,

I am having a stroked 496 BB on the engine stand and I am in the middle of choosing the heads for it. I already have stock 440Source heads that flow on intake [Email]290CFM@.600[/Email] valve lift, exhaust [Email]220CFM@.600[/Email] lift.

I just ran into CNC ported 440Source heads that flow a little better, intake [Email]315CFM@.600[/Email] lift, exhaust [Email]233CFM@.600[/Email] lift.

The cam I am going to use will give almost .600 lift on the valve with 1.6 rockers

The flow rate difference between these two heads is not a big one, on intakes 25CFM and exhausts 13 CFM. in percentages it's 8.5% and 6%.

By experience can you estimate how much the head flow increase will effect to the HP rating?

I know that exact numbers can't be given, but it would be nice to hear your experiences or real figures if you have had your engines dynoed after a head change.

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Try to get some mid lift #s from .300-.500 and compare the two. make sure your not sacrificing #s at mid lift to get A good upper lift #s if you are the 315 will be A instant loss of power. If you cant get it sooner your not going to get it later.

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So I guess giving more cam to the engine would give better HP/$$ ratio ???

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The cam can affect the power band, more duration tends to take away bottom end and add on the upper end to some extent, lobe seperation angle has similar affects also I would look at a cam with 250 to 265 degrees at .050 on a 106 to 110 lobe seperation angle with as mauch lobe lift that I could get for your motor That kind of cam will sound pretty nasty at idle and up to 2000 RPM, widening the lobe angle will tend to calm it down some down low in the RPM band while raising the peak torque and HP RPM I did a head swap on my street motor in my Duster, 512 low deck. I took off a set of ported 906 iron heads with big valves and put on a set of CNC Eddy RPM heads with the same size valves as the 906 had, the 906 intakes flowed 266 at .600 on a Super Flow 600 bench, the Eddy heads intakes flowed 310 at .600 on the same bench. The car ran a best of 10.69 ET at 124.5 MPH with the iron heads and ran 10.43 at 128.6 MPH with the Eddy heads I did swap rockers from a set of CAT 1.6 aluminum rollers(check to be only 1.54 at the retainers ) due to shaft wear to a set of Harland Sharp 1.6 aluminum roller that check out to be 1.64 at the retainers Buy the good heads now

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My question is how is the engine going to be used?
If your racing with it and need the extra power, then spend the $$$$ and port the heads, use a large cam, and setup the converter/gear to work with it.
If it is a street car, how often will it really be raced, and how could the extra $$$$ be better spent or saved?

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It's a 1970 Challenger, mainly a street car, but occasionally used at 1/4 mile or stop light races.

Here's some specs of the engine and drivetrain, Comp XR292HR-10 hydraulic roller cam, 1.6 roller rockers, 2" headers, MP M1 intake, B&M 3000 rpm stall, 3,55 gears

My target is to run with it to mid or high 11's. That would be enough to fill my appetite for speed, atleast for a short time

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I think 440source numbers right out of the box are way bogus. I hand ported a set of 440 source and can tell you they are way optimistic on their OOTB numbers.
Hears what a Friend got stock now this flow bench may be a tad stingy (hope it is by my indy head flow numbers)

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Those are interesting figures.

Looks like the flow was not much increased after the .400 lift, only 10 CFM to .500 and from .500 to .700 lift almost the same rate ~244/5 CFM

Anyone else having similar results?

440Source is marketing that those heads flow 290CFM @.600 OOTB

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440Source is marketing that those heads flow 290CFM @.600 OOTB

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My question is how is the engine going to be used?
If your racing with it and need the extra power, then spend the $$$$ and port the heads, use a large cam, and setup the converter/gear to work with it.
If it is a street car, how often will it really be raced, and how could the extra $$$$ be better spent or saved?

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It's a 1970 Challenger, mainly a street car, but occasionally used at 1/4 mile or stop light races.

Here's some specs of the engine and drivetrain, Comp XR292HR-10 hydraulic roller cam, 1.6 roller rockers, 2" headers, MP M1 intake, B&M 3000 rpm stall, 3,55 gears

My target is to run with it to mid or high 11's. That would be enough to fill my appetite for speed, atleast for a short time

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Hello,

You will get what you want with them stock more than likely. I would not CNC port them at this time. Save the bucks and pocket port and you will hit your mark for sure.

Damon