I have a 72 Mach 1 with a 351 cleveland that is in need of a rebuild. For street use, nothing extreem, just under 400hp i would think/hope. It currently has open chamber 2V heads. A few years of researching online has directed me towards using the Aussie, closed chamber 2V cylinder heads because of their higher compression. However, after speaking with the guy who would be doing the rebuild, I realize that the combustion chamber of the open chamber head is much larger, thus flowing more air, thus more power??? His recomendation is to keep the open chamber heads becausethey will provide more air flow, and just use domed pistons to get the compression ration up. Makes sense to me, but then again, im a noob;p But, I have heard that the 2V heads tend to ping a lot. Can this beavoided? Is there any other reason that I would want to go with the Aussie heads?? What would the experts(you guys) recomend?

Thanks!!

 

A couple things....unless you are paraphrasing and simply trying to convey something that you aren't really what he said....get a new builder.

With that said...he might simply be trying to save you a little money. You can make a fun little ride with lots of power using the heads you have. The trick with the aussie heads is when you aren't doing a full rebuild to put them on and it ups the compression for more power. If you are changing pistons already, it is just as easy to reach a target compression with the heads you have.

 

A few things, what is your budget, when you say rebuild are you saying new crank, rods, pistons, heads, intake-all the good stuff, or kind of a take it apart, clean it up, new bearings rings and gaskets, and put it back together. I think that should be your first decision after you know how far you want to take it then parts can start being selected.

 

Also the difference is that open chamber heads have a combustion chamber that looks like a circle, the valves are unshrouded more than closed chamber heads, and the spark plug location is laid back. Closed chamber heads have "double circle" chamber, basically it looks like a girl with one boob higher and smaller than the other. It also has a quench area on both sides of the chamber.Yes open chambers do flow better but you have to consider everything, cam, bore, stroke, valve size, heads-remember its all a package not just heads.

 

btw, flat top or dished pistons also produce more power than a domed piston if you can keep the compression the same via chamber size. its a trade off really.

personally, i'd ****** a set of aussie heads if you can find a set cheap. if not, grab something with a small dome and do the best you can with your current heads.

either way, you need to have a little time spent cleaning up the ports especially where the short turn radius is right under the head of the valve.

 

Thank you all for your replies!! As far as the kind of rebuild im thinking, I believe he will be usinga master rebuild kit that will replace everythingexcept the crank. The block will be bored .030 over. Im looking at a 4bbl carb(i believe around 650cfm), weiland excellerator intake, headers, anddual pattern cam with around .510 lift(forgot duration but i remember it wasnt much more than stock). We are shooting for around 9.5:1CR Hope thats helps... So, would an open chamber setup like this provide much more power than a closed chamber setup, both running the same compression? Will a larger combustion chamber provide more power than a smaller closed chamber with the same compression ratio?

Thanks again!

 

dude roller cam it theres at least 50 to 75 hp just in this swap alone, i recently done it and man! it actually idles smoother than my old 268h cam and it has more lift and duration, and the power is awesome, has a completely different tone, and is much louder! but if i had the money id go for the chi heads. the open chamber heads will get the job done while keeping comp at a reasonable level, my m-code has the quench chambers and monstrous valves and with 93 octane its just barely cutting it. the 2 brl ports will give you better bottem end torque than with the 4 brl heads making it more streetable. the problem with the quench chamber head is that the chamber is actually too small, and its shrouds the valves but it still makes really good power, the open chamber heads dont shroud the valves nearly as bad but the size of the chamber tends to create 2 flame fronts causing pinging, this can be somewhat cured by removing all th rough casting marks in the chamber and smoothing all rough edges, but thats a whole nother story! if there running the same piston then the quench will make more power, due to more compression and larger valves although the 4 brl cars dont come alive till they hit about 3 grand and from there they just keep pulling

 

lol @ my77stangs avy.