1971 Buick 455 GS F/SA G/SA Build

[HP HUNTER]

At this point I have the intake side of my head where I want it, its time to look at the exhaust side. Intake valve size is 2.005 on 315/330 HP 455. Valve job is 30/45/60 30 degree back cut on the valve.

[goinbroke2]

Originally Posted by HP HUNTER

At this point I have the intake side of my head where I want it, its time to look at the exhaust side. Intake valve size is 2.005 on 315/330 HP 455. Valve job is 30/45/60 30 degree back cut on the valve.

Really? 30/45/60 30degree back cut.....so a normal 3 angle cut? Did you flow the different angles and the 45 seat with 30/60 on either side flowed the best? That's interesting and certainly not what I was expecting. Having never seen the chamber I'll assume from that, that the chamber is big enough to not shroud the valve. (or the valve is small enough to not need the help)?

How wide did you make the seat?

From what others experienced with Pontiac's mimicking sbf flow characteristics, I thought the buick would follow suit. Apparently not!

Excellent, keep it going, let's see what the exh needs!

[GTOMayhem]

goingbroke you have a PM

Thanks
Rick Thomason
GTOMayhem

[HP HUNTER]

Originally Posted by goinbroke2

Really? 30/45/60 30degree back cut.....so a normal 3 angle cut? Did you flow the different angles and the 45 seat with 30/60 on either side flowed the best? That's interesting and certainly not what I was expecting. Having never seen the chamber I'll assume from that, that the chamber is big enough to not shroud the valve. (or the valve is small enough to not need the help)?

How wide did you make the seat?

From what others experienced with Pontiac's mimicking sbf flow characteristics, I thought the buick would follow suit. Apparently not!

Excellent, keep it going, let's see what the exh needs!

I wouldn't say my angles are optimum, but I was happy with my gains from the previous setup. The 45 was .040 wide. Its important to note the engine as run as tested (474 HP) in this thread had flow numbers @ 28" of

.200 131.9
.300 185
.400 211.7

Which leads me to this: 176 CFM @ 28" through the intake manifold @ .400 lift, which makes me wonder if there is lofting of the valve involved as mentioned by a friend?