Hey Francis – Great idea to go a bit “non-traditional” with your build. The 1985 and newer Chevy 4.3L; (262ci) V-6 is as you have suggested, a small-block V8 without the number 3 and 6 cylinders. There are a zillion of them out there left over from S-10 pickups and Astro Vans so the stock parts are plentiful. On the “go fast” side of the equation, it sounds like you’ve already tapped into Edelbrock for carburetor and manifold. Good call on the Headmans as well.

You may also know that the bores are 4.40” centers and the deck height is 9.025” (sound familiar?). In 1985, the 4.3L went to the same bore and stroke as a 350 V-8 (4.0” x 3.48”). The, oil pump, main and cam bearings, pistons, all of the valve train parts, and timing cover from a SBC will fit perfectly.

350 pistons are a natural upgrade. Do your homework on compression ratio, quench, gaskets, etc., up front – Stock heads are 68cc and stock C/R is about 8.5 - 8.8:1. With very little work, and a Fel-Pro .040” gasket, 9:1+ is attainable and you’ll be able to still run pump gas with no problems. The rods are 5.7” like the 350, but have a larger journal size (2.250” versus 2.100”) so make sure you plan accordingly if you’re going to swap rods. The stockers are really pretty good and your machine shop can clean them up, resize and shot-peen them (may be some disagreement here, but quite simply, shot-peening rods makes the rods more durable by strengthening the metal and reducing fatigue). The 4.3L is an internally balanced engine and uses the same harmonic damper(s) as a 350.

Comp Cams has a plethora of cam kits for the 4.3 but I’m a bit on the conservative side here not knowing what your overall build will look like. Summit Part number K18-124-4 has the following: cam, lifters, valve train, (hydraulic flat tappets, springs, seals, and clips – no pushrods). The advertised Duration 268/268, Lift .454/.454. Price is about 300 bucks. Note that the springs in the kit are 1.43” diameter and the heads need to be machined to accept them. The .454 lift may be a bit tight as well and I’d have the machinist relieve that and install 3/8” screw-in studs (since we’re already there!).

Summit carries quite a few 4.3 parts as do the guys at Six Banger Performance (http://www.sixbangerparts.com/chevv6performanceparts)

GM Performance parts catalog shows a lot of parts to ranging from aluminum blocks and heads, to special intake manifolds – but know going in that GM is really proud of their parts.

Brodix makes aluminum heads that bolt on and are designed for the Edelbrock intake manifold http://www.brodix.com/heads/v6.html.

Little work and this thing will sound great, push real close to 300HP, and in a nice light bucket run like grease through a hot tin horn!

Have Fun!
Glenn