Elliott S.

Anyone actually have the Arao heads on their car? The Grand Prix community is finally getting better heads. Arao is making us some 4 valve Aluminum heads for around $4500. There has been some doubt as to the effectivness of the 4 valve heads over the 2 valves. I can look at graphs all day long, but individual experiences is where its at. Do they actually perform as to what they advertise? The worst part on the Grand Prixs are the crappy 2 valve heads. Our best ported race head is outflowed by a stock inline 4 2.4L grand am head. Ive searched, but all i could find is that they look good and look promising. Any real world experience? thanks

ShiftyCapone

iTrader: (7)

You may want to try another forum. I doubt you will have much luck asking the wrong crowd.

CraZ-28

Sorry bro, completely different drive-train on these boards.

Elliott S.

i wasnt asking about the drivetrain, i was asking in general how much better (if at all) the increase in the number of valves have helped SBCs. We're just trying to figure out if it will be worth it or not. I wasnt asking you guys on how they would work on L67/L36 engines, just if they actually worked on SBC engines or not. Just gauging whether they help in real life, or just in charts

ShiftyCapone

iTrader: (7)

The benifits of a DOHC cam motor are too numerous to mention in one post. There are certain aspects of it that are unmatched when compaied to a 2 valve IC engine. However there are trade off for both. You cannot simply convert a SBC to run 4 valves. it is an entirely different mechanical system. I would check out a few IC engines books to see the comparison between the two. Don't be fooled by power output alone as your determining factor. Many 2 valve systems can produce the same power as DOHC set-ups. The differences lie in efficiecny and changes in your typical IC engine power curves.

JPrevost

The arao heads aren't DOHC, they're still pushrod and no you can't make as much horsepower with 2 valves compared to 4, it's just more air flow and a better chamber design (fast burn to the max).
I haven't seen arao heads in person but I have held and inspected their first design heads when they went under the name D__something something. I want to say Delphi but that doesn't sound right. Anyways, yes 4 valves per cylinder is superior in every way shape and form compared to 2 valve heads. Why do you think EVERY high specific output motor HAS 4 valves per cylinder... it's because they flow air, lots of it.
Horsepower is how much air you can fit into the combustion chamber. Ideally you'd want no popet valve and a port with the same cross-sectional area as your bore, but that's impossible , so the alternative is adding valves/ports since the flow potential of more area is just that, more potential... which CAN (usually does) lead to more air. Add the fuel and you make more horsepower, nothing new.
DOHC, pushrod, they all do the same exact thing only in different ways. The DOHC design is more reliable at high engine speeds is the only benifit, at low engine speeds it actually costs you more power than a well designed pushrod setup, it's ALL about efficiencies. DOHC doesn't have the momentum of the rocker arm, pushrod, and lifter so it can use lighter weight springs and rev to the moon where as a pushrod has less rotating weight (usually) which takes less horsepower (since spining up a heavy object takes power).
All in all I'm a firm believer in heads, it's where the horsepower potential is made and yes, bigger IS better when you want horsepower.

Marc 85Z28

iTrader: (3)

Dominion

Elliot S. - If you're looking into the Arao heads, have a look at Coates' heads. I don't know if they have a website.