Power gained by additional cam lift?

[djr48312]

I have a situation a 4v DOHC head with the following flow numbers:

.200 175 125
.250 205 148
.300 225 154
.350 250 165
.400 262 170
.450 270 172

Stock cam is 206@.05" 248 advertised with .309 lift where the head flows 225CFM,

How much power would be gained by lifting it out to where the head flows over 260cfm so for example .425 or .450" lift? We wouldn't increase duration too much maybe 216@.050" with 256 advertised.

I know in the situation if the heads were the limiter and it was a 300-350HP v8 with say a performer rpm 2 intake 750 holley, good exhaust and a 220@.05" cam and say you took a 220CFM set of heads and replaced them with a 265CFM set of heads the power gain would certainly be over 30HP possibly up to 50HP.

[mag2555]

In your last paragraph here’s what could be had assuming everything is ideal for each level of flow your taking about there, and with the detail of either one having the needed minimum port area to control the port velocity.

220 cfm@28” could get you 56hp per cyl, or 450 hp out of 8 cylinders.

265 cfm@28” could get you 68 Hp per cylinder, or 545 hp from a v8.

[djr48312]

In your last paragraph here’s what could be had assuming everything is ideal for each level of flow your taking about there, and with the detail of either one having the needed minimum port area to control the port velocity.

220 cfm@28” could get you 56hp per cyl, or 450 hp out of 8 cylinders.

265 cfm@28” could get you 68 Hp per cylinder, or 545 hp from a v8.

So are we expecting it to gain additional HP as if we replaced a 220CFM head witha 265cfm head at the same lift point?

[KnightEngines]

It depends entirely on how much air the engine wants!
If 225cfm is more than enough to feed it there will be no gain.
If it really wants 300cfm then the gain will be substantial.
Post up the full specs of the engine & what sort of power range (rpm) it works in, me or someone else with pipemax can run it through & see what it wants.

[djr48312]

This particular engine is known to respond with 30HP by porting the heads to 301cfm@.450", and using the low lift stock camshaft. it gains 25CFM @ .300" in that porting job. So i figured that stock heads would gain by using a higher lift cam that lifts it to where it flows in the 260's versus the stocker where it flows around 220cfm.

[CamKing]

It depends entirely on how much air the engine wants!
If 225cfm is more than enough to feed it there will be no gain.
If it really wants 300cfm then the gain will be substantial.
Post up the full specs of the engine & what sort of power range (rpm) it works in, me or someone else with pipemax can run it through & see what it wants.

exactly.

[pcnsd]

This particular engine is known to respond with 30HP by porting the heads to 301cfm@.450", and using the low lift stock camshaft. it gains 25CFM @ .300" in that porting job. So i figured that stock heads would gain by using a higher lift cam that lifts it to where it flows in the 260's versus the stocker where it flows around 220cfm.

A few thoughts.
More specificity is needed for a reasonable attempt at a semi-accurate response.
Inlet time/area targets can be increased by both lift and duration. Because valve train acceleration is limited by things like lifter/bucket/roller diameter, increasing lift will possibly/probably come with some increased in duration as a consequence.
Increased inlet efficiency will reduce pumping losses, but the most probable result of a inlet restricted motor being served greater mass will be an increase in the rpm of peak HP.
The common flow=HP empiricism equations are dated and biased by the weighting of push rod 2V V8's used in their creation. (JMO) You may do better.