360-1 Indy 245 cnc heads

Justin..... def one of those “it depends” things.

Those were on a 408 motor, which only had a 4.030 bore.
I doubt that little difference would amount to anything(.015” per side).

I did that test on an Indy 440-1 cnc345.
4.375 bore vs 4.500 bore.
Zero difference on the intake side.
The exhaust picked up a couple of cfm way up at the top.

I tested a fully ported T/A head(that someone else ported) on my 4.00” bore adapter and the numbers were noticeably lower than what the owner was told they flowed.
And, frankly..... they “looked” like they would have been better than what they were.
There was speculation that perhaps the other shop tested them on a 4.250” bore(the motor the heads were on had a 4.00” bore), so I retested on the 4.250 adapter.
Almost identical to the 4.00” test......... but slightly lower numbers at higher lifts.