Valves adjusted to tight.
Firing order mixed up.
either your timing is off or your valves still need adjustment
are you sure its just a blown head gasket?... if heads are warped due to overheating replacing the gasket wont help you will need new heads as well. You can get a Haynes Manual or Chiltons, they will give you step by step guidance on replacing your gasket.
they came with "186" casting number heads.........
Yes they are the same heads.
There are many places where one could purchase small block Chevy heads. Some of the best places to purchase small block Chevy heads at places like Amazon or Auto Zone.
Yes, and well.
NO.
Yes they will, but 305 heads have a smaller combustion chamber so it may raise your compression ratio.
These should be double hump heads. They are very sought after heads.
It may need a new throttle positioning sensor, or the temp control plug it is located on the intake manifold towards the front, also may be timing, the gunk may be oil so your valve seals in the heads might be bad, good luck.
The best practices for maintaining and replacing guitar tuning machine heads include regularly cleaning and lubricating them, checking for any signs of wear or damage, and replacing them if they no longer hold tune properly. It is important to use the correct tools and follow the manufacturer's instructions when replacing tuning machine heads to ensure proper installation.
305 heads of course, 350 heads will fit for sure and possibly 400. obviously no big block heads will fit. a 305 with 400 heads gets you a little over 352. 350 with 400 heads is a 383. add and divide