64 vs 69 305e

[Jduckett]

Hi all.

Can someone please tell me the difference between a 64 and a 69 305e if any?
Thanks for you help. Jeff

[bigblockv6]

There was a horsepower increase from 142 net hp to 157 in 1966 as well as different cam timing, a newer style fuel pump and eccentric. In 68 the ventilation system changed, the breather from the back of the block was eliminated & capped off and new a breather cap with tube ran from the passenger side valve cover to the air cleaner. Thermostatic air cleaner was added to 1/2 ton models in 68, though none of these changes took place in 69, the 69 305E was basically identical to the 68 305E.

[Jduckett]

Thanks for the reply. Are the engine internals the same with the exception of the time chain and gear set? Pistons, rods, cam and crank. Is the crankcase breather port gone on the 69 or just plugged allowing it to be made to appear as a 64 block. I thinking of buying a 69 engine for parts for my 64.

Thanks again. Jeff

[bigblockv6]

The internals are the same with the exception of the timing chain and sprocket. As far as the engine breather hole all GMC did was capped it of with an expansion plug.

[Jduckett]

Nice. So I can assume if I put the newer timing sprockets I would theoretically see an increase in horsepower.

Thanks Jeff.

[bigblockv6]

The cam profile is different on 66 and up engines so you won't have any increase in power on the 64 305.

[TJ's GMC]

You'll like the 69 better. lol

[Jduckett]

Just so I'm straight. A 66 and up cam will with the chain and gear will work in a 64 block. I trying to keep the original motor with the truck.

Thanks Jeff

[bigblockv6]

Yes it will work! The thing for you to know is there were no major internal changes made to these engines in the entire run from 1960-74. GMC thrived on interchangeability on these engines. The biggest change was done in 1973 when the 478 got a bigger main journal crankshaft making it impossible to use an earlier crank only on 73-74 478 engines, yet you could turn down the 73-74 crank journals and use that crank in earlier blocks, in fact that's what I did with my 478.