It’s not that the 350 is a dud when ‘built’ even in those heavy, square late 70’s pickups ( I owned a 78 Scottsdale once upon a time after building a pretty stout 350, I pulled it out for a 454) so where I sitting is putting a 383 stroker is only a few bucks more and will deliver a lot more torque which is what most pickup owners are searching for.
The 350 for the year have and really from 1972 to 1996 is a pretty neutered motor even without EGR as on some models. The root problem being low compression, a lazy cam, hardyly any ignition advance, lean carburetion combined with really lazy burning, overly large combustion chambers. These are the thinks that need to be addressed, emission equipment takes all the blame but compared to the lack of the performance fundamentals in the design of the major components of these engines, power losses to emission equipments is somewhere in the minor noise level. You need to fix the fundamentals not the bolt on factory junk. Not that you shouldn’t remove that stuff if you can, but removal alone won’t change much in terms of torque and power. This applies to your 350 and whether you use it as a 383 base build.
I have no idea what copper head gaskets would do by themselves, they are usually applied to high output engines that require the cylinders be O ringed to insure the compression seal, otherwise these things tend to leak what you can’t afford to lose.
Basically you need to get the compression up, these days that falls pretty hard on cylinder head and piston selection. Everything else just tails into that. To that end your basically looking at heads whether factory like the L31 Vortec of 1996 or the plethora of import and domestic aftermarket heads. The piston crown shape makes the bottom side of the chamber; the factory round dish being the least efficient burner of mixture, the flat top or D dish are quantum’s better at converting mixture to power. The other criticality is squish/quench clearance between the surfaces of the piston crown and the step of the combustion chamber. The less area overlap as occurs with a round dish piston combined with a greater clearance for any piston shape the more prone the engine is to detonation and preignition. So maximizing the effects of squish/quench builds what is called mechanical octane which permits getting more power from the fuels at the corner station. Done right this makes the fuel behave as if it’s octane is 4 to 7 points higher than its pump rating.
To pull this off takes some prior planning as the squish/quench clearance needs to be from .035 to .045 inch for a street engine. This counts the distance of piston crown to the deck and the thickness of the head gasket. For a cast iron head this isn’t too hard to deal with as there a several steel shim gaskets that are .015 to .019 inch in thickness that gets a standard block and piston/rod assembly beck clearance of .020 to .025 inch into the neighborhood of the total clearance. But if you choose an aluminum head then you’re looking having to use a thicker composite gasket the thinnest being .026 inch. This forces you into getting the block’s head decks milled (called “decking“) so this trip wire need to be thought out ahead of time.
Most makers of aftermarket heads also duplicate what the make in aluminum in cast iron as well, so there is some flexibility here.
The L31 Vortec factory head uses a unique intake bolt pattern so these add an intake purchase to your parts list most aftermarket heads are machined for the 1955 through 1986 bolt pattern and the Vortec 1996 through current crate engines of that style. The 1987 through 1995 is an oddball that looks like the early pattern but changes the angle on the bolts by the plenum, just something to watch out for as there are sellers that try to pass off these oddball 87-95 LO3 and LO5 heads as Vortec’s, so you need to keep your wits about you when head shopping. The LO3 and L30 are the shrunken head versions for the 305 in those years.
Come back with questions, they are easier and cheaper to answer than it is to correct bad decisions.
Bogie
www.jegs.com
