PRHeads
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This is a 346 head, but will give you an idea......
If you do more than this for a mild small cam build, you’re probably wasting time and wearing out tools for no gain.
Stock pinch = .975”
Reworked pinch = 1.060”
The pinch work was a 7cfm gain.
(My recollection is that the 516 head has a wider pinch area than the later heads)
With a back cut OE 2.08” valve the port in the pics flowed:
[email protected]/[email protected]/[email protected]
For comparison, a gently used 452 head(factory valve and valve job) flowed:
[email protected]/[email protected]/[email protected]
For another comparison....... the big valve 906’s I had on my old 448, that made 535hp and ran low 11’s....... that I ported before I had a flow bench, and just used some guidance from a guy who did porting for a shop I was working at........ the 8 cylinder average(which I determined later on after buying a flow bench) was...... a whopping 239cfm.
I had spent quite a bit of time on those too.
If you do more than this for a mild small cam build, you’re probably wasting time and wearing out tools for no gain.
Stock pinch = .975”
Reworked pinch = 1.060”
The pinch work was a 7cfm gain.
(My recollection is that the 516 head has a wider pinch area than the later heads)
With a back cut OE 2.08” valve the port in the pics flowed:
[email protected]/[email protected]/[email protected]
For comparison, a gently used 452 head(factory valve and valve job) flowed:
[email protected]/[email protected]/[email protected]
For another comparison....... the big valve 906’s I had on my old 448, that made 535hp and ran low 11’s....... that I ported before I had a flow bench, and just used some guidance from a guy who did porting for a shop I was working at........ the 8 cylinder average(which I determined later on after buying a flow bench) was...... a whopping 239cfm.
I had spent quite a bit of time on those too.
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