[Gary H]

Originally Posted by steve25

So I have two sets of 47 castings to port up.
One set had been fitted with 2.11” intakes and 1.77” exh valves .

The set I am posting up the flow results from the pair that still have there stock 1.96” intakes with a 45 degree seat and there stock 1.66” exh.

The exh numbers this head produced yesterday out of a end port where so surprising that I repeated the flow test again today to rule out fluke numbers that might have happened.

Note that the 47 casting has a date code of A 21 9, while the other head is this pair has a date of L 10 8.

Here are the stock flow numbers from this end port in the first column, and in the second column are the flow numbers from a stock 1971 96 casting with its 1.77” exh valve.

It’s too bad these 47 casting where not made with a 2.11” valve.

Flow @ 28”

.050”. 42.7
.100”. 62. 50.2
.150”. 86.5
.200”. 111.8. 95
.250”. 132.2.
.300”. 148.6. 128.2
.350”. 158.6
.400”. 167.4. 158.4
.450”. 174.3. 152.9
.500”. 180.3. 161
.550”. 184.2. 163.7
.600”. 188.2. 166.4

That's difference is pretty incredible. Is the port shape or valve bowl area noticeably different between the two?