Re: Camel Hump Heads on a 307???
 

Not to pull my math nerd card here, but the CR calc is pretty straightforward.

Here is the overly simplified version, assuming a piston top dish volume of 12cc and head gasket volume of 8cc...

1) Convert your engine displacement to cc: 307*3785/231=5030cc
2) Divide by number of cylinders: 5030/8=629cc displacement per cylinder
3) Take or measure your clearance volume (how much water does it take to fill your combustion chamber) in cc. A 1960s high performance head will have around 64cc. Add the volume of the dish 12cc and head gasket 8cc to get 84cc.

4) Then take total volume at BDC (clearance volume + displacement volume) and divide by total volume at TDC (clearance volume). (629+84)/84 = 8.5

You can then adjust any of these if you use a different head or dish/dome configuration. And better yet, if you can measure any of these you'll get a more trustworthy number.

EDIT: P.S., and if you have a domed piston and you know the volume of the dome, you subtract that from the head volume.

Re: Camel Hump Heads on a 307???
 

If 307's really come with 76cc heads, then going to 58cc 305 heads will up the compression a bunch yes. If you are only starting with 8.5:1 compression though, that's not always a bad thing.

That being said, 305 heads have small valves. I wouldn't run them unless they were vortec 305 heads which still flow decent.

Re: Camel Hump Heads on a 307???
 

Ok, my old heads were at my cousin's house, I sold him a bunch of parts and threw the heads in for free. The heads that came off my motor were 70 cc chambers not 76. I can get them back for free but don't really want to to use them.
I'm pretty sure they came with factory shim gaskets and the piston isn't very far down the hole. The motor was suppose to have 9 to 1 compression. I really would like close to 10:1, 64 cc with a shim gasket should get me close shouldn't it. My goal is no less than 9.5:1 and not over 10:1.
I really would like around 300 hp but with the factory heads and a good cam and four barrel carb I figure I would be around 250 hp. It looks like the extra 50 hp is going to cost me around $1000, not sure if it's worth it.
Oh yeah, the pistons are flat top, no dish.

Re: Camel Hump Heads on a 307???
 

I have been gathering parts, found an GM factory aluminum intake and trying to talk a friend out of a set of 601 high compression 305 heads. I also have a used quadrojet that looked clean but not tampered with on the way. I'm hoping to rebuild it but if nothing else I will use it for parts.
In the mean time I decided to do a little termite damage repair on my shop. I knew they had gotten in the frame around my doors but wasn't overly concerned because I had planned to enlarge the doors anyway. Well it was a lot worse than I thought.
https://photos.app.goo.gl/ZQak5qQvMzKJybrN8