Yeah, that seems to be a very common statement. Thanks mate. I don't really intend on making any part of the port bigger, just plan on making it how it would be had the casting been better. I will not lower the floor.

 

The original design was not bad, but rough foundry work and addition of smog bumps usually made a mess of the ports. If you smooth off the smog bumps and open the gasket surface to the original contour of the port they work pretty well.

 

I had no idea there were two types of smog bump. Which years had which?

 

Wasn't a year thing, so much as which foundry/engine plant.

 

bowl work, blending into ports and under the valve really help sbf heads, it takes some majojor work to get them to flow good though, id look into aftermarket heads even gt-40's unless you are experienced at porting heads, otherwise grind the bumps off and do a gasket match about 1" into the head, you might see 10hp if your lucky.

Frankly a cam (especially a custom one) will give much more improvement than a gasket match, a dual pattern cam with 10-15 degs more exhaust duration and 108-110 lca with a higher lift rocker on the exhaust will wake up a poor flowing head.

 

But a poor flowing head won't take full advantage of a better cam.

 

Yeah mate I am doing bowl work as well. My question was whether or not the hole for the gas recirculation would effect flow. But thanks

That's right!

 

Was it only Californian heads which actually had a hole for the gas recirculation? Did the others just have a provision for it?

 

Yeah, there were a lot of heads that had the bumps, but were not drilled for the injectors. Whether they were drilled or not, the exhaust flow was pretty bad. I'd estimate the improvement at more than 10hp on smog heads, I believe I got more than that on my non-smog 65 heads.