Musthaveboost

Looking at stock casting # heads and stock angle heads VS after market 11 and 13.5 degree heads

i see that the 11 and 13.5 heads flow better on the intake

but on the 15 degree heads but the 15's flow better than the 11/13.5 on the exhaust side.

Heads were tested in 28" of water.

So what are some of the advantages and disadvantages between the different angle heads?

SOMbitch

iTrader: (8)

The 13.5/TFS and 11/ETP have much better PTV so you can run thinner gaskets for better quench, mill more for compression and still run a bigger cam.

Never really noticed less exhaust flow (and I am too lazy to look up right now) but 75%-80% or so of intake flow is considered optimal.

silver01z06

Generally the 11 and 13.5 are better flowing. I have not paid that much attention to actual exhaust side flow numbers but it would be strange would have worse flowing numbers. The advantages of the 11 and 13.5 is better flow and standing the valve up straighter. This allows you more piston to valve clearance. More clearance allows you to run bigger cams and not have to do things like fly cut or worry so much about interferance.

The heads that have the 11 and 13.5 valve degree are after market heads. The after market head companies have taken the gm castings and improved them. They have made design changes that help make more power and its not just in the cnc/porting work. An example is trickflow moved the spark plug location to improve spark according to them. Anyway look at what other people have done and proven to work and not work. If you want to be the experimental guy go ahead. I would just rather do it and know it will make power.