I am thinking of putting E-Tec heads on my engine instead of Vortecs. Since the Vortecs have a 63cc chamber and the E-Tecs have 64cc chambers there should not be a significant change in compression, but I planned this engine out based on almost 10:1 compression with d-dish pistons, .038" piston-to-head clearance and multiport EFI so it would run on pump gas with the Vortec heads.
Ususally aluminum heads increase performance by allowing a higher compression ratio, but they actually reduce efficiency slightly by allowing more of the combustion heat to exit into the cooling system instead of pushing the piston.
So, does anyone know what will happen by making this change?

<font face="Arial,Verdana" size="2">Originally posted by GetMore:
So, does anyone know what will happen by making this change?</font>

You will save about 45 pounds off the nose of the car and make more power with the E-Tecs. They flow better than Vortecs, especially on the exhaust side.

The thermal effiency stuff is probably true in theory, on the street it means next to nothing. JMO.

If you have the bucks then go for it. Aluminum heads also look better at shows, etc. Again, JMO.


[This message has been edited by MikeM79 (edited September 10, 2005).]

IMHO the heat doesn't just transfer to the cooling system, it also transfers into the intake and carb heating both air and fuel. Have a good cold air and cool fuel strategy with Aluminum.

the biggest draw back with Al heads, $$

Fuel milage SUCKS with aluminum heads.

There is no magic in the aluminum and yes heat is power and the aluminum does transfer heat away from the chamber. So a nice hot iron head 'should' make more power than an identical head poured from aluminum. BUT,, the fact is aluminum is the choice of manufacturers because it's more workable, production costs are less and the obvious weight thing. SO most all performance heads are aluminum not just for those reasons, but repairability. If your dumping $2-4k in a set of performance pieces for your motor,,,it's comforting to know damage can be welded up, machined back down and your back in business. That's also one of the big reasons the aftermarket uses aluminum is the ease of machining to make a repeatable design, head after head after head. Not so easy to do with casting iron.

So why does fuel milage suck with aluminum heads??? I think it's chemistry! ,, and part of that 'left brain vs right foot' connection. Something in the aluminum enhances the excitement of the pleasure centers in the brain when the right foot goes WFO and allows the aluminum heads to do what they were designed for http://www.nastyz28.com/ubb/wink.gif

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Interesting physics Marv akin to the apparant, gravitational mascons found just under the accelerator pedals on most Camaros. I never considered the easier repairability of aluminum. Its a good point. I didn't get aluminum over basically the price of good ones and I have an orange painted sleeper appearance I'm working towards. A good cool air strategy is important on any car. I'll never understand the words "fuel economy" and "high performance" used in the same sentence.

<font face="Arial,Verdana" size="2">Originally posted by Marv Davis:
Fuel milage SUCKS with aluminum heads.
</font>

Marv, I was getting ready to really launch a verbal assault until I read the rest of your post! You are the master!

Marv I was just about to disagree with you until I read the end of your post.But now I totally agree http://www.nastyz28.com/ubb/smile.gif .GetMore i dont know what the rest of your combination is but if you get the 170`s I cant tell you this.Be prpared to have a permanet http://www.nastyz28.com/ubb/smile.gif on your face cause those heads are just awsome.On a sidenot about fuel milage I`m getting roughly 17-18 mpg on the highway.

Andy

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355 10.5 TO 1,E-Tec 170 Heads,Super Victor Intake,Proform 750DP Race Carb,Comp Cams Pro Magnum 1.6 and 1.5 RR,Comp Cams 285B6 Cam,3.42 Gear,10 Inch Converter,2 1/2 Exhaust,Dynomax Race Welded Ultraflows.
Best ET:11.84
Best MPH:115.05
Best 60Ft:1.609
3500 Pounds With me

The nearly constant flame inside the cylinder negates the SUPPOSED thermal loss of aluminum heads.

Its an Old wives tale that the unknowing keep passing along. That's why you see it written in the Car Rags like HotRod Car Craft etc.

<font face="Arial,Verdana" size="2">Originally posted by hhott71:
The nearly constant flame inside the cylinder negates the SUPPOSED thermal loss of aluminum heads.

Its an Old wives tale that the unknowing keep passing along. That's why you see it written in the Car Rags like HotRod Car Craft etc.</font>

Then please explain to me why an engine with iron heads will make more power then an identical engine with aluminum heads? Compression, cam, ports, valves and every other part is the same except the head material.

Haven't ever seen conclusive proof of more power with iron vs aluminum

Any magazine test that does show a whopping 5hp difference is followed by a Full Page ad from the winner of the shoot-out.

Im sure that if more power was to be had and since the car MUST weigh in at 2350 lbs anyway
The Pro Stock cars would have Iron heads,, but yet they don't.

<font face="Arial,Verdana" size="2">Originally posted by Joekool:
Then please explain to me why an engine with iron heads will make more power then an identical engine with aluminum heads? Compression, cam, ports, valves and every other part is the same except the head material. </font>

Show me the tests and we can discuss. I have never seen a test with identical heads that has proven the power advantage/disadvantage.