aftermarket aluminum heads

[kelly theaker]

i have for some time now contemplated putting a set of alum, heads on my 69 tri-power 427 , . the vehicle is starting to run well . i continue to fine tune the
carbs and timing but i am always looking for more performance . I believe the heads were 118cc, rectangular port and had been ported before my ownership. i ask for your oppinions , are the aluminums just a weight savings and a timing advantage or do they offer this and additional torque and h/p.

[Gene M.]

Re: aftermarket aluminum heads

Kelly,
If you are refering to the new GM over the counter aluminum heads you should see an improvement. Most of it would depend on cam and header selection. If you are refering to the old L89 heads there would be far less notice in street performance over the stock cast iron. Remember intake and exhaust must balance to see maximum benefit. Corked or choked exhaust will hurt horse power the most.

[Warren F.]

Re: aftermarket aluminum heads

Kelly:

There is definitely a difference other than just weight savings, between the original L89 heads and the original (Corvette) LS6 heads. There is a difference in the intake port contours as well as less shrouding around the spark plug areas in the combustion chamber areas. Exhaust shape ports changed to accomodate for header styling match ups then.

Most Corvette magazines with written articles on the different aluminum heads for L71/l89, early/late L88, ZL1, & LS6, show that the ZL1, late L88 & LS6 heads flowed 10 to 15% better than the L89 & early L88 heads.

[kelly theaker]

Re: aftermarket aluminum heads

i was referring more to an edelbrock or other brand name alum heads/ Brodix , are they of similar flow or not , any one have feedback ? I am currently running the stock L71 heads and thought winter is on its way maybe a switch to aluminum and put the others on shelf . Just looking for a small project . How about the GM units , are they a better quality unit or is everyone using the same technologies that GM has engineered. I understand that GM is using Edelbrock to cast and finish their heads . This is a street driven piece and as correct as i am aware of untill judging shows different.

[Clem Z.]

do not forget that you must

raise the CR .5 when going to aluminum heads from CI to get the same HP because of the better cooling of the combustion chambers in the aluminum heads. remember heat is HP and you loose combution chamber heat with aluminum heads. you best bet if you are looking for max HP is to have the head chambers coated to prevent the heat loss.

[Steve Antonucci]

Re: do not forget that you must

Clem,

Can you comment ( with details please ) on the coating of the chambers?
What type of coating, who does this, how long will it last, etc.....

Steve

[Clem Z.]

to save me a lot of typing which i am slow

go to www.calicocoatings.com and click on coatings at the top of the page