Originally Posted by Joel78Vette
I have a SBC 2 bolt-350 bored .030" over with 062 vortec heads (now 175cc intake runners and 60.2cc chambers) with stock valves (yes 3 angled), after-market springs (1.265" singles) set at 122#'s, 7/16" studs with guide plates; cast steel crankshaft, eagle rods, flat top, 4 valve relief, hyper-eutectic pistons; polished professional products cyclone intake (dual plane good to 5500 rpm's) topped off with a stock 650 thunder series edelbrock carb. The camshaft is a Howard's Race cam (retro roller)-214/218@.050", .488/.495" lift w stainless steel 1.6 full roller rockers. Quench is about .057". about .016" in the hole with a .041" gasket (1003, I believe). Static compression sits about 10:1 at 1700 ft above sea level. I have a full 2 1/4" hooker exhaust with 1 5/8" - 3" ceramic coated headers. A level 2 700r4 w 2200 stall converter and 3.55 rear gears on 27" tires (255/60r15). The block mains have been aligned honed and have studs vs. bolts. Good Hp and TQ numbers would be appreciated. Thanks, Joel
Nice combo, I'd say hp is somewhere in the 375 to 400 range around 5600 to 5800 RPM, torque around 390 to 410 about 3500 to 4000 RPM.
Pluses on everything, except the intake and carb and to a lesser extent quench.
Negatives are the intake and carb. The Edlebrock Performer RPM and a 750 Holley would give more top end power with very little sacrifice on the bottom end. I know the calculators on CFM for a 355 lead one to about a 600 to 650 cfm carb but you'd find the bigger Holley or Edlebrock/Carter will better support a 400 plus horse top end, if indeed you want to crack that somewhat of a bragging right barrier.
The squish/quench could have been tighter which would be more effective if it was .040 inch. But the compression really isn't that off, my calculator produces 10.3 Static with a rounding to 60ccs in the head and assumes 6 cc's in the pistons. The dynamic assumes a 5.7 inch rod and I calculate the Howards 110235-12 really doesn't close the valve tight on the seat till 61 degrees After Bottom Center. This is a long ramped cam from the .050 inch lift point on the intake being 266 at zero (or there abouts) and 213 from .050 inch tells you there's 53 degrees of ramp between those two points. Assuming the cam is symmetrical that's 26.5 degrees on either end of the lobe from .050 to zip. Subtracting that from my 61 degrees you get 35 (then take out 4 for the advanced grind nets 31 which I didn't do)
which is pretty close to someone’s calculation of closing at .050 which would not take into the dynamic effect of the rising piston shoving high pressure mixture past the almost, but not quite, closed intake valve. This effect is nothing like flow benching intake flow at .050 inch lift with a pressure depression of 28 inches of water. This is more like where compression goes with a burnt exhaust valve, that's a substantial pressure loss, 'cause the piston is pushing mixture out. So anyway running my personal DCR calculator it drives an effective stroke of 2.79 inches which reduces the 10.3 SCR to a Dynamic Compression Ratio of 8.46. Certainly 93 octane unleaded burning in an L31 Vortec chamber ought to be good with this. Perhaps not ideal but certainly acceptable within the context of a street performance engine which at least for a DD can't be taken to the same operation/configurational edge that a race engine can be pushed against.
So I'd say this is a darn good effort. Well thought out; you're to be congratulated.
I’ll sort of PS this; where some claim to run less than .040 inch squish/quench, this gets risky in that one can easily bang the pistons and valves and at high RPM the piston to head structure. For a street engine that will wear and that includes the softening of the valve springs with age, running under .040 can result in unpleasant and expensive experiences.