Originally Posted by ryder57
Ok so I started taking the 307 apart and inspected the heads and they are not 305 heads. They are the "882" casting number heads with the big valves. Should put them in the 350 block and build it since they are bigger heads?
these are the worst SBC heads there are. The cr was extemely low with these heads on a 307 and they flow like crap.
Find a cylinder head with a small combustion chamber.
882 heads are useless and usually cracked too..
If the valves are 1.94x 1.50 and usable keep them and the retainers and locks.
If small 1.72" valves diameter ditch the heads whole.
Find a better head.
On the 307 bring the piston to TDC exactly and measure the piston deck clearance @ TDC.
This will be a whole different motor with a high compression cylinder head on it.
With a 882 head on it its no surprise your friend gave it to you. It would be a very lame motor.
You can fix that.
If you want any chance of using the thumpr cam in a 307 working well you need a high compression ratio+ head port flow
stiff gears and a converter.
You want a cylinder head with a real 53cc to 58cc chamber volume (measured) and a thin .015" head gasket.
The 307's piston deck clearance @TDC matters.