690 vs 817 heads on a dyno!

El Rat

Well Known Member
#1
My position is if you limit the RPM to 6000 you get more HP and torque with 817 heads. Obviously I am basing my position on 40+ years of racing.
One quick story: back in the early 80’s a famous head guru took one of the Buick configured heads for a SBC and epoxied the intake runner to raise the velocity. The problem with the Buick’s is/was they wouldn’t make power above 8000. The SBC Buick’s had a tall rectangular port and the thinking was if they could raise the short turn radius and thus make the port similar to a conventional SBC racing head they would get the best of both worlds. Well the head took a crap it made torque off the chart but wouldn’t rev over 6000. As an aside the head guru built the heads for Bernstein’s INDY car effort # 1 qualifier at Indy and crashed on the pace lap. What a maroon!
 

DonSSDD

Well Known Member
Supporting Member 2
#8
I think the 61 409 and the 62 409 had the same cam. The heads and intake were different.
61 was 360hp. 62 409hp.
Chevy frequently tinkered with advertised hp numbers for various reasons, it would be interesting to see dyno numbers. Hell of a coincidence a 409 made 409 hp for instance. What is the difference between a 62 409-409 and a 63 409-425?
 

dakota tom

Well Known Member
Supporting Member 1
#11
Chevy frequently tinkered with advertised hp numbers for various reasons, it would be interesting to see dyno numbers. Hell of a coincidence a 409 made 409 hp for instance. What is the difference between a 62 409-409 and a 63 409-425?
63 had more cam duration and lift. Better exhaust manifolds but hp numbers are probably with headers. 63 had single point distributor with vacume advance.
 

425/409ER

Well Known Member
#12
I wonder how a 690 head would work if one filled the port floor with epoxy and raised it up so the port would be more like a raised runner head. I bet it would make more power as from what I see some do with the SBC intake ports for the S/S crowd.
 
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