I know these are not the best motors but I have a set of 305 torker heads and a nice new RV cam best suited to a small engine. And other goodies like an intake, carb and headers.


I can get a nicley rebuilt 307 (Chevy not olds) with flattop pistons for about 600 bucks or a stock rebult 305 for 500.

So, given the parts I have kicking around what short block would do me best?

I would like to keep my world heads since I paid a decent price for them. They are model 42650 I think.
So thats why I am sticking with a 5.0. Plus It should be better on gas than a 5.7 right?

I know everyone is going to say go with a 350 but if I keep my 58cc 305 torker heads what compression ratio 350 would I have to go with in order to avoid needing premuim gas?

 

What is this engine going in, the car or truck? I would think if they both had the same heads and cam the 305 would get a tiny bit more MPG do to the smaller bore and therefore it has less piston ring surface and would have less friction, but the 307 would make better upper RPM power due to the larger bore and less valve shrouding. As far as compression you should use one of the many online calculators to figure it out.

 

think of the friction and pistons speeds related to having a longer stroke though
adding more stroke to a motor makes the WHOLE RING travel that much further causing a lot more friction then just adding a little more ring from a larger bore.

 

Right now the motor will be going into my car...but I may put it in my truck down the road when I can afford a new 350 for the car. See the truck has over 250k on it and burns oil, I don't use it much anymore but I would like to keep it.

 

Generally speaking, the smaller the bore the greater the potential for good fuel economy. The flame front has less distance to travel away from the spark plug the smaller the bore is. More of the A/F mix will be consumed during combustion- less chance some of it can "hide out" far away from the plug. Hence, greater efficiency, greater economy.

That would be the 305.