It’s an interesting comparison
. (first engine)
9.5 cr
063 closed chamber oval port heads, 2.19/1.88 valves
750 holley
Edl Air Gap
hydraulic roller cam from cstraub, 242/254; .655/.640, 108 lsa
1 7/8 super comps
1†spacer
Results with 91 octane fuel:
518 hp @ 5500
543 tq @4200
(second engine)
13.1 cr
closed chamber rectangular port heads, 2.25/1.88 valves
BG 950
Holley Strip Dominator
Solid Flat tappet, 256/266; .600/.620
2 1/4 headers
2†spacer
Results with race gas:
584 hp @ 6800
509 tq @ 5100
a point to think about
you normally gain about an average of 3.5% in hp for every point of compression added
518hp at 9.5:1 sure is not bad, and you can use pump high test fuel and theres a 3.6 point higher compression ratio on the larger duration, and higher cpr combo,, 3.5% x 3.6 points in compression equals about a 12.6% gain in horsepower due to the increased compression alone, 518hp x 1.125 increase from compression increases=582 hp, Id have expected more from the smaller roller combo, the added duration, larger ports, higher compression, larger exhaust, and the swap to a single plane intake and larger carb,on the second engine mostly accounts for the higher rpm and lower torque peak, on the larger duration second engine combo, the 2.25" exhaust is too large for a 427 displacement, (that hurts scavenging of the cylinders) and a good dual plane intake probably would still have worked reasonably well on the large rectangular port combo
. (first engine)
9.5 cr
063 closed chamber oval port heads, 2.19/1.88 valves
750 holley
Edl Air Gap
hydraulic roller cam from cstraub, 242/254; .655/.640, 108 lsa
1 7/8 super comps
1†spacer
Results with 91 octane fuel:
518 hp @ 5500
543 tq @4200
(second engine)
13.1 cr
closed chamber rectangular port heads, 2.25/1.88 valves
BG 950
Holley Strip Dominator
Solid Flat tappet, 256/266; .600/.620
2 1/4 headers
2†spacer
Results with race gas:
584 hp @ 6800
509 tq @ 5100
a point to think about
you normally gain about an average of 3.5% in hp for every point of compression added
518hp at 9.5:1 sure is not bad, and you can use pump high test fuel and theres a 3.6 point higher compression ratio on the larger duration, and higher cpr combo,, 3.5% x 3.6 points in compression equals about a 12.6% gain in horsepower due to the increased compression alone, 518hp x 1.125 increase from compression increases=582 hp, Id have expected more from the smaller roller combo, the added duration, larger ports, higher compression, larger exhaust, and the swap to a single plane intake and larger carb,on the second engine mostly accounts for the higher rpm and lower torque peak, on the larger duration second engine combo, the 2.25" exhaust is too large for a 427 displacement, (that hurts scavenging of the cylinders) and a good dual plane intake probably would still have worked reasonably well on the large rectangular port combo