Head selection

1)- The extra 45-or-so horses comes mostly from the higher compression. But the closed chamber combustion chamber shape is a more efficient shape so that contributes, too. Many closed chamber heads are machined for an adjustable valvetrain which contributes to even more efficiency and power (with more aftermarket parts). There are closed chamber 2V type and closed-chamber 4V types. This last is the legendary "Boss-351" head. There are also aluminum versions from SVO and P.I Motorsports, that reduce engine weight subtantially for better handling, are easily repairable via welding and are already machined for an adjustable valvetrain. Iron 2V or 4V heads are scarce and nearly as pricey as aluminum while being virtually unrepairable if things go wrong inside.

2)- not necessarily, although adding the full "Boss" conversion with roller rockers will allow the use of mechanical cams in place of the hydraulic type, etc. Full roller rockers decrease the engine's loaded oil temps by 15-20 degrees, but add no extra power. Reduced oil temp is valuable at very high engine loads such as in competition.

3)- Whether you do this of not is a personal choice. Some guys are content to run 'only' 275-or-so horses and 150 mph in 5th. Others are not satisfied until they can run away & hide from that $78,000 Viper down the block. Your call....

Jack! I would beg to differ. If the roller rockers lower the friction across the valve stem and at the fulcrum, and take less Horsepower to run; does this not "Free-Up" a few extra Horsepower?? Regards, Marlin.

You know, 150 mph in 5th at this point in my life is pretty okay with me. I enjoy your responses to my questions because my sense is you drive your car much like I do. On the street, with my wife driving or not, maybe an occasional rally but that's it. The car already has tremendous acceleration and I can stay close to another family members Viper. I think I'm going to conserve cash and stay with the heads and the compression ratio I have for the time being.

Out of curiosity, which heads are on your current motor?

Joel
(another northern Calif. person)

I currently run a pair of SVO A-3 aluminum heads in our '72 L. I added them not for the power increase, but as part of an intensive campaign to lower the weight of our stock-appearing, flair-less, wing-less Pantera for better handling. The alloy heads, the required SVO open-plenum intake and a few other mods dropped 100 lbs off the engine wt. At this date, our Pantera L, with radio, AC etc weighs in at 2760 lbs- some 400 lbs less than it was as-delivered. The compression ratio is 10.5:1 and depending on the way I drive, 87-octane doesn't ping (due to aluminum's much better heat dissapation eliminatimng hot spots in the heads) but when I feel frisky, a tankful of 92 octane is better for it. The engine is 14 years old.

[Jack! I would beg to differ. If the roller rockers lower the friction across the valve stem and at the fulcrum, and take less Horsepower to run; does this not "Free-Up" a few extra Horsepower?? Regards, Marlin.]

Yes, probably, but for power increases of 1% or less on a 300-horse engine, you'll never see such an increase on the street. As I said, even racers add roller rockers simply for the better efficiency, the reduction of valve-guide wear and the cooling effect on the oil supply.