Originally Posted by wildeman
I have asked this question a while back, but now I have some more info on my motor. I currently have a 355 sbc with SR torquer heads (76cc, 2.02/1.6, 171cc intake runners) street port/polish, an Edelbrock Victor Jr, Holley 750 vacuum sec., Lunati cam with .480 lift int/exh 292 adv dur, 230@.050., and Sealed Power L2256F30 pistons. The motor came assembled with the Fel-pro blue gaskets (.040) and the motor is claimed to be a 10:1 400hp. With the heads, I'm thinking its about 370 and 8.5:1. I swapped out the gaskets for
.015 steel shim gaskets, but I figure I'm running around 9:1. I've been looking at the Patriot pn2168 aluminum head to get that 400hp or slightly more. Would these heads be a good choice or is there better for around the same price?
As you describe this engine would be very close to one we dynoed the specs were:
Engine 362 horse 355
Crankshaft GM cast
Con Rod 5.7 GM Pink
Piston Old TRW Pwr Forged F/T, 4 reliefs
Rings 2 x 5/64 Moly, 1x3/16
Head 340292, 64 cc, ported, angle plug
SCR 10.0:1 (.025 deck, .019 gasket)
Intake valve 2.02” Back Cut 30/Polished
Exhaust Valve 1.6” Back Cut 30
Rocker 1.6:1 Comp Stainless Roller
Cam Comp Magnum 280, 230/.480 I&E 110LSA
Carb 750 Holley
Exhaust 1-5/8 Long Tube
Torque 370@ 4500
Horsepower 362 @ 5800
The 292 head uses a smaller 64 cc but old fashion chamber so your Torquer's larger chamber while you probably need a few more degrees of advance the end result between them should be close.
The old Comp 280 cam in terms of duration and lift at the valve from .050 is close to the Lunati 292; I'd expect similar performance between them.
Your Victor Jr will out breathe our Performer, but given the limits of head flow and combustion efficiency downstream of the intake I rather doubt the bottom end can work the Victor Jr anywhere close to its capabilities to deliver mixtures to the cylinders so its presence is a moot point in my mind.
Your piston selection is identical to the old TRW Power Forged with the same old wide rings just with a coating on the skirts. My experience shows that skirt coatings are not where most piston friction is; that's in the ring pack, the skirts hold a pretty good oil wedge between themselves and the cylinder wall. A narrower ring pack and lighter tension rings nets measurably less friction but drive other tricks to seal over the long haul on street motors and really push the limits on windage control technology. A high volume/pressure oil pump, stock oil pan with narrow low tension rings will build you an oil burner.
So all-in-all I think your guess at 370 is in the ball park. The Patriot 2168 head will bring a much better configured (Vortecish) combustion chamber which will pick up the power with no other changes. The aluminum will let you push the compression up which the rampy cam you have needs as for its duration it takes it forever to close the intake valve. Back cutting the valves, especially the intake greatly, improves low lift flow for a rampy cam working a 1.6 rocker can have good advantage to improve flow as the valve is opening and closing on these long ramps.
Hopefully you measured deck to crown clearance while the heads were off, this distance from .025 OEM to maybe zero as remachined plays a heavy part in the compression ratio as well as the squish/quench effectiviness.