Chevy 250 Opala,
I am glad you are trying the upper lumps.
I hope it turns out good for you.
Also, just remember, even if you do not see a huge gain on the flow bench does not mean your engine will not be much difference performance wise.
I saw a gain in CFM on the flow bench machine but I think I felt the gain more by actually installing them in my Camaro & driving it.
For the exhaust port,,, I believe you just add material to the floor of the port,(the short turn radius)
You would need to heat up the cylinder head to a certain temperature somewhere between 200 & 300 degrees, & I think even higher than 300 degrees???? (don't quote me on the temps)ask people who do that type of brazing. then apply brazing rod material & slowly bring down the cylinder head temperature,,the heads have a tendancy to crack though. Not so much when you are using a new casting.
The exhaust port does not flow that bad as compared to the intake.
So basically try to do most of your improvements on your intake side, that is where you are going to make more power.
Not saying don't try & improve the exhaust port flow,just your gains will be more pronounced with your intake improvements.
Goodluck!
MBHD
