I really need to know the difference between these 2 heads besides the intake valve size. I don't have the casting # in front of me, so make it a general statement. thanks

 

Chamber size, port flow.

305's being smaller in both cases.

 

Do you think that is purely because of the valve size? or are the ports actually smaller?

 

From what I understand, it's not just valve size.

But, someone chimed in not too long ago that with porting work, the 305 types flow well. Of course, with 350 Vortecs, only the exhaust need work, so it sounds like you have to do a lot of work to the 305's to get them to flow as well as unworked 350's.

But, none of that is said with personal experience with either.

 

The ones I have worked with came off a 2000 to 2002 chevy van. Forget the casting # though. Stock the intake side of the vortec 305 heads flow almost as good as the 350s. The exhaust port is the same. The ports are identical just the valve sizes are different. The 305 has 1.84 & 1.50 valves where the 350 has 1.94 & 1.50. The chambers are similar it is just missing the little protrusion on the side oposite the spark plug. Also the chamber is 58cc vs. 64. The increased compression would probably more than make up for the little loss of flow.

I helped a buddy drill steam holes in a set and put them on a 400 in a late 70s 4x4 truck. We also stuck in a comp xtreme 4x4 cam in it. It could spin all 4 tires from a dead stop. Engine pulls easily to 5,000 so flow couldn't be too bad.