What is the differnce between low cc and high cc heads

[Robry 87]

I have 60cc 305 heads on my 350 would i be better to run a stock 167cc headswith 1.94" intake valves and 1.50" exhaust.
But the new heads do not come with valves can i replace Thom with better after market parts,or can you guy's recommend so heads type and specks i should look for.I have a bracketmaster II cam 2000-5500 performer RPM intake,holly 700 carb, MSD ignition with hooker headers,3" exhaust.

[VileZambonie]

Not really sure what you are asking man.... No offense but You need to work on your grammar.

I think you are asking if 60CC heads or 76cc heads are better for your 350?

The 305 heads have smaller valves, ports, etc and will not flow as well. True a smaller combustion chamber typically packs a harder punch but you need volumetric efficiency. Get more air in get more power. I wouldn't run the 305 heads

[HAULIN IT]

Rob, I'm a little confused about the 167cc, there is no such item. The small block used many between 58cc & 76cc, now these are "advertised" numbers so they may vary slightly. The cc refers to the amount of air mixture or fluid for measuring you can fit in the chamber with a plate covering the deck surface, the deeper the valves are sunk,ect. the more cc will be in the combustion chamber. The bigger the combustion chamber the lower the compression (without changing anything else) also the larger chambers retain more heat because of the larger area. The ideal way to go is a flattop piston (or dished) to get the proper ratio you want/need. The cc of the head isn't the whole story, other factors such as port flow & valve sizes along with quality of the casting are all things to concider. Lorne

[SUX2BU99]

I think I know where he's getting confused. There are two cc measurements to take note of: combustion chamber volume in cc and intake runner volume in cc.  Numbers like 58, 60, 64, 72, and 76 cc are for combustion chambers. Bigger the number, the larger the chamber and the lower the resulting compression ratio (piston and rod length unchanging). With intake runner volumes, the bigger the number, the higher the flow, but the lower the velocity especially at lower RPMs. So, heads that are larger than say 180cc would make for a fairly high powerband which isn't always desireable in a heavier vehicle. Just my opinion.

305 heads have a smaller bore than a 350, so their combustion chamber cc's are smaller, like 58cc. That's not necessarily a good thing because their valves are shrouded and are difficult to make as much power as a larger chamber head for a 350 with it's larger bore. Not saying it can't make the power, it just makes it more difficult. Most performance heads have a chamber cc of around 64 to get the compression ratio up.

[Robry 87]

Look my grammer is not the best so. But my manners are so let me try agean.
 I have a 350 with 305 heads that are 60cc.My   magazine shows a replacement head that is 167cc, for my 350 and i do have flat top piston i don't no what type.i just wanted to no the difference.
  I'm just looking for so insight on heads and what i should look for?

[Captkaos]

What magazine are you talking about and what is the part number for the heads.  305 closed chamber heads are ok if you don't plan to go over about 5000rpms...

[Robry 87]

THE MAGAZINE'S NAME IS   TRUCK, AND THE PART # IS 30-7433 THANKS FOR YOUR REPLIES

[HAULIN IT]

Rob, I believe as Sux was saying, your getting combustion chamber cc's & intake runner cc's confused. Who makes this head? That is not a GM part number, must be an aftermarket company. You should either go back a read somemore or try to post a picture of the ad/article. We will be glad to help, just need a little more info. Lorne

[Robry 87]

I'll post some pic of the  heads i have and the one's i saw in the magazine and then you guy's can expline the difference to me. cool