I am ready to buy a set of heads and cam. I have a 400 bored .30 over to a 406. I am looking at the dart Pro-1 Alumin heads with  64cc combustion chamber. I am also looking at the Comp Cams Mutha Thumper cam with .299 int and 319 exh duration. The lift is int .531 and exh .517 with a loibe seperation of 107deg. Does this sound like a decent power combo. I think if I run a thin head gasket it should up my compression ration from the 9:5:1 up to right around 11:5:1 (it has 76cc heads on it now). I am looking to see what other type of heads and cam combo option that maybe better for about the same price. I am looking for about a 500 or 550hp combo with a very rough idle and good horse power! Any thoughts???  

The last thing you want to do on a 400 block is run thin head gaskets. Because of the siamesed bores and water jacket design, 400s are sensitive to overheating issues. Running a thin head gasket might put you at risk for some problems.

If you want to increase your compression ratio, order a set of heads with a smaller combusiton chamber, or just have hte heads you want to buy milled down for higher compression.

If you're gonna drive the car on the street, that cam could be trouble with the 107-deg lobe seperation. The motor won't make a lot of vaccum, so power brakes and other vacuum dependent accessories are going to have trouble working. I'd give the Comp tech line a call, tell them exactly what you want the car to do and how you're going to drive it, and see what they recommend. If the car's going ot be driven on the street, I wouldn't go below a 110-deg lobe sep angle.  

You know it all depends on what you're going to do with this. A race only engine running leaded race fuel will handle 11.5 compression, my quick and dirty calculation is closer to 11.8 with 64cc chambers .025 deck clearance and a .025 gasket. Unleaded swill at 91 or 92 octane won't deal with this.

Since you're buying new heads I'd select a chamber size that doesn't require messing with odd gasket selections. The 400 does better with a composition gasket and aluminum heads require it rather than steel shim gaskets. So start with the deck clearance and gasket thickness, converted to volumes and calculate backwards from there for chamber volume. High compression and steel shim gaskets isn't a real good combination anyway. I mean it's OK for a race motor where you're going to be in it frequently, but a street motor where you may want to go somewhere further than a quarter mile away can become a problem keeping compression and fluids in.

Bogie  

I called Comp cams and they advised me to go with the mid size thumpr cam ( 291/311 dur and 521/507 lift. They said other then that the cam and heads looked like a good Combo but when i called summitt they tld me the Pro-1 Alum heads were to big for a street application unless i was plaining on running 13:1 compression. I asked the summit guy if he could tell me what heads i should look for that would giv me the max Horse/Torq that wold match to that cam. He didnt tell me anything specific just to keep the runner down around 200cc and compression around 64cc heads i i would be fine. So now i am confuse and starting over looking for heads so I'll pose the question to anyone here. Is there a set of heads that someone could recomend for me. I would like them to match the cam because after 55GUY told me about the cam i went onto the web sight and i like the way the rough idle sounds. The motor is in a 79 camaro It was my very first car when i turned 16 many years ago) It is only a toy that will be mainly cruised to the local cruise night but will see a little bit of track time. I want something that will give me the most amount of horse's for the buck.
I have started looking at cast heads and Alum heads i do not have a real preference I dont think the 40 or 50 pounds that i would save on Alum heads is that important for my application. Any suggestions?  

Give the guys at Comp a call, and ask them if they have a head from their RHS line that'll match up with your cam and intake you want and will make the power you want.

The general rule with a cam to head match is big ports/small cam, small ports/big cam.