[DeTomaso] Stock 4V Heads vs alloy

[JDeRyke at aol.com]

As you mentioned, the 35 lb per head weight-savings is one big advantage- 
both in physically handing the castings and for the car's improved center of 
gravity. Along with the intake manifold, the heads are the heaviest 
high-mounted parts in your Pantera. 
A second is infinite repairability; I've heard of alloy heads BROKEN IN 
HALF that were successfully rewelded. 
Third: the most desirable head configuration is the closed-chamber Boss 
type and all alloy heads come this way. Converting any common iron heads to 
Boss specs will cost close to the price of alloy heads. Reproducing the 
high-efficiency alloy head exhaust ports in any iron head is impossible.
Fourth, iron heads- even closed-chamber Boss heads- aren't very stiff; 
during the '69-'72 period when 351-Cs were being professionally raced, NASCAR 
shop mechanics developed a number of internal braces for the combustion 
chambers to keep them from flexing at high rpm/high compression running. All 
Cleveland cylinder heads are thin-wall construction just like the blocks; some 
heads flexed enough to reverse the flow of cooling water through the engine! 
This led to unexplained overheating and head cracking. The required mods 
called 'posting' are outlined in Waddell Wilson's racing engine prep book; Jr 
Johnson also had similar brace techniques. 
Finally, the cooling characteristics of alloy heads are far superior to any 
iron heads; so much so that one can usually run 1/2 to 1 full point of 
compression HIGHER than even a fully modified iron racing head. In these days of 
low octane tractor fuel being sold as premium gas for many dollars per 
gallon, being able to run pump gas without engine damage is certainly worth 
consideration! The only time iron heads should even be considered is if 
high-boost turbocharging is in your future. Iron heads retain more heat and boost 
than alloy heads- if you can keep the rest of the engine together.... 
My 2¢- J DeRyke (with SVO heads on the street since 1990)