hi guys i am almost done restoring my 67 gs340 for the scond time and was wondering i have an iron headed 2brl 300 i just got an aluminum intake and was wondering if i could bolt on the aluminm heads with out any problems will the rockers bolt up i already know about the diffrence in port size and figure that if the 64 had 250 hp the should have know problem handing mine another thing will these heads change the compresion ratio o is the piston the diffrece between the two. thanks alot you guys have been a big help
It has been years, but I think I should know this. Am pretty sure you can use the 64 heads/manifold on the 65-67 300 block (not a 340!). Check the heads/head gaskets to the block passages. If my memory is correct, the 65-67 blocks have an addional casting to seal an opening in the later heads that is not there on the 64 heads. You can't go the other way around putting later heads on the 64 block. The later heads have a water port that will be open (even if you use the 65-67 head gasket) as there is no casting in the block to sandwich the gasket. The only other questions that comes to mind is the pushrods. This all depends on the deck height of the motor. Not sure if you need 64 pushrods or the 65-67 ones. My guess is you will need 64 one, but maybe someone else can confirm this. Rockers should be the same. Hope this helps, Mark
I'm confused. You start off by talking about a GS 340 and then mention having a 300 block. Are you strictly speaking about modifying a 300 engine; or, are you talking about using various mixed 300 parts on a 340 block?
I ran into this exact issue (putting a set of cast iron '65 heads on my '64 block). Didn't notice the extra water port until I had the engine together & fired it up. Water drained right out of the extra head water port - this was very disappointing after spending months collecting engine parts, assembling & getting everything just right. I had a machine shop plug the hole on the head with a threaded plug, put everything back together again & it's fine now. I wish I would have known this beforehand, would have saved me a huge headache of having to pull apart the top-end again.
re 300? thanks for the info guys your always a big help sorry about the confusion the car is a gs340 but the original motor is gone and was replaced with the 300 i am thinking about doing this swap only if it is possible without a great amout of work thanks again adam
