Which head/combustion chamber is better for performance? Speed master aluminum LA or aftermarket magnum iron head?

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pittsburghracer said:
Out of the box Speedmaster heads are in the 250cfm area. I’m betting a J or X head can be made to flow better than that but be prepared to pay a handsome price. I could do a set for free (or close to free) and I’m not even interested.
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I have the interest if you have the free!?
 
rebelcaptain said:
Mentioned were Edelbroor Performer, TrickFlow, Speedmaster and ProMax heads. What about the 1970 and 71 stock 340 heads with the large 2.02 valves? Are any of those aftermarket heads better/worse? The literatures says "increased performance". Performance doesn't necessarily effect gas mileage. What's the story?
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My impression of an AJ response!:

Not sure where you want to compromise regarding fuel efficiency, performance, and budget -the first two categories move in the opposite direction.

Much of this is obvious but for review:

More gears in your transmission, with a steep first gear so you can run an axle gear closer to highway gears.

For example
Mopar 833 (2.66) with 3.73 rear= 9.9218
Tremec TKX 3.27 with a 3.0 rear= 9.81
Close in first gear launch yet the 3.0 axle with a .73 overdrive gear will get you that performance and fuel economy.

There is more to torque converter selection that I simply don’t know-perhaps the higher stall converters are less efficient than stock???
A999 904 autos come with a 2.75? First gear versus 2.45/2.48? Typical auto first gear-again am out of my element


My guess, smaller, more efficient intake runners (heads and intake), in comparison to engine displacement size, along with compression, and specific camshaft point towards fuel efficiency.

I don’t enough where air speed becomes too turbulent in these intake runners-the geniuses here would have to tell you where to draw the line with a 273/318/340/360/37X/408/416 etc.



So closed chambers should support more compression- so more fuel efficiency.

Fuel econ people run small carbs-again not in the direction of performance-how much performance or fuel economy do you want?



Cam intake lift at .050” at 204 starts the torque at 700 rpm (where yellow rose said don’t lower your engine idle any lower than that.) But no one here runs a cam that small (like 318willrun ‘s crane cams 693901 or 693902 cam/cam lifters) for performance unless (like 318willrun’s scenario of 2.45 gears) they are running highway gears

Some books like intake and exhaust valve sizes closer in size to each other for fuel efficiency .

Valve job seems to do as much as head porting-you get both Econ and performance with this.

Obviously:
Lighter car,
Wheel size that matches engine and cam size

There are hundreds of books on this broad trade off.

As RustyRatRod would say, “hit the books!”

Or maybe get a discertation from AJ as I just took a swing at performance versus gas mileage.

I don’t think doing anything that increases fuel air consumption will support economy-only improving efficiency of the process.

I think birdsong on YouTube got 20++ mpg with a 440+cubic inch B body with ?3.23? Gears
Someone can correct me on that.

Bert wishes
 
pittsburghracer said:
Out of the box Speedmaster heads are in the 250cfm area. I’m betting a J or X head can be made to flow better than that but be prepared to pay a handsome price. I could do a set for free (or close to free) and I’m not even interested.
Click to expand...
Yeah you got slant 6 heads to do. lol
 
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