splashandburn

I'm in the process of doing some updates on my HP500EFI's (200 hours), head gaskets, springs and a valve job. While I have the heads off is there any advantage to replacing these with aluminm heads? Will I see any performance gains by doing just the heads? Thanks for any input.

splashandburn

Anyone?

JCPERF

You could pick up an easy 50 HP with a cylinder head swap.The weight difference is considerable by going to the aluminum heads.

formula31

http://server2.boatfreaks.org/forums...&threadid=3148

Dont know if this link is kosher but too much info for me to cut and paste

splashandburn

Thanks for the link - it did work but now I'm really confused. This link kinda says that the cast iron heads will make more power than the aluminum if all else is equal. Are the Edelbrock aluminum heads that much different than the cast iron heads so as to make a positive hp gain? Thanks again.

GPM

You would definatly see a power gain with a good set of CNCed aluminum heads I would be looking at a 320 cc intake runner, probably the 2.25 intake valve, the 2.3
may cost you some bottom end. You might want to look at m2race.com for some ideas. I personaly don't care for canfield or edelbrock.

formula31

Dont feel like the lone ranger. I was thinking of going from well ported 049's ovals with 119 cc chambers to the 110 cc edelbrock chambers and was told that I would gain nothing but less weight.

So if you were going to go from iron to aluminum with the same chamber size (like the rect.) you would have to get a bigger dome piston just to stay equal.

Obviously, I chose to stay with the iron.

formula31

Of course, assuming the runners and flows are the same, More flow is not always a good thing and can hurt, velocity is more critical for most of our engines unless you want to spin them high.

GPM

Velocity is important, but airflow makes the power, cubic inch and RPM dictate maxium air flow and horsepower. You only need roughly 250 cfm per cylinder [8]
to make 500hp. The smaller the cam, the less flow thru intake and head, the less
hp potential of the motor. Better heads, .600 plus cam, ported intake, 600hp@5600
Once again only an opinion.

Raylar

Being a cylinder head manufacturer I will throw in my two cents here! I am assuming from your location you could be boating in seawater. Unless you are very careful and generous with your freshwater flushing or have closed cooling the use of any aluminum heads that are at least hard anodized should be carefully considered, they will take more maintenance than iron with raw water cooling. If you choose aluminum hard anodized heads and you reduce your chamber size by about 10cc.,you can gain an extra point of compression on the same fuel and add at least 25-30 horsepower alone. Your engine can develop even more power from aluminum heads with good combustion chamber design, high velocity-high flow ports, quality valves, seats, and valve job than it does with your GM iron heads. As for the weight savings, my expierence tells me that in most cases the boats performance improvement will be negligable if any. Weight distribution within the boat is far more important. As for good aluminum cylinder heads, my personal opinion is that Edelbrock, Canfield, Dart, Merlin and Brodix all make good cast aluminum big block heads and some of these even offer hard anodizing and special marine duty valves, however I feel that the heads from AFR and Profiler are definitly better in terms of flow, port velocity, casting quality and overall fit and finish. For the most part one of the other reasons aluminum heads offer more power is the fact that they have been subjected to more development improvements than the iron heads they replace. Newer port and combustion chamber designs, cnc programs and manufacturing improvements have made the big block aluminum high performance heads a better value for todays performance boater.
Just some straight skinney!
Ray @ Raylar