some gm service head for the corvette,,semi closed chamber.its been to long to remember the p/n.

So to clarify for OP and follow thread, these WERE NOT peanut port heads, correct?

correct,,large ovals.

Any idea what is the primary runner lenght/diameter off gill/stainles marine manifolds? Cant find any info.

First flow test done. Step 1. Intakes: slightly cleaned valve throat. Exhaust: stock. Test pressure 10", results converted to 28"



Head casting: 14092360.

good port
​​​​​0.100=65cfm
0.200=144cfm
0.300=207.5cfm
0.400=243cfm
0.500=263cfm
0.550=266cfm
0.600=266cfm
​​​​​​

bad port
0.100=62.5cfm
0.200=145.5cfm
0.300=211.5cfm
0.400=233cfm
0.500=244.5cfm
0.550=251cfm
0.600=252.5cfm

Exhaust, no pipe.
0.100=50cfm
0.200=94cfm
0.300=128cfm
0.400=157cfm
0.500=175cfm
0.550=180cfm
0.600=185cfm

What you thing about ferrea 5000 series valves? Planned to use 6000 series valves but ferrea dont offer 1.72" exhaust valve, 1.88" is the smallest.

try rev,manley and even PEP automotive parts,they may have a quality stainless steel valve.

https://www.summitracing.com/parts/slp-v-1989x