That's pretty damn good. I built a SBC 415 stroker around 10-12 years ago. If I was lucky I got 5 MPG.
Its the cam, tires, and the q-jet, and the mercy shown to the footfeed.
The cam is, even though billet and pretty to the eye, actually tiny. Really tiny. And the q-jet, a very nice one from SMI, acts like a typical q-jet. Pretty easy on the gas until you flush. The tires I had on it when I was driving it, were 31 inchers. It has a stock converter paired with the 700r4, and the lockup functions, so that helps also. When I built the engine, I used keith black pistons that are dished with a D shape, designed for the vortec head style combustion chamber. Full floaters with circlips.
They look something like this:
I calculated roughly 9.8 to one compression with the head gasket I used. I did use 1.6 roller rockers instead of 1.5, for a little extra, but only a little. It was more happenstance than anything else, as were most of the other parts. The oil pan I had laying around, from the blazer - a 4.3 v6 pan cut and rewelded with the JTR extension and redrilled with v8 oil pan rails. The block was given to me by a local farmer. The crank, rods, pistons, cam, rockers, gauges, centerbolt cast valve covers, intake, carb, timing cover (cast aluminum), water pump (aluminum reverse rotation) balancer (summit), were all late night ebay specials. Pennies on the dollar, the parts cost me. The intake and piston/rings/pins set were like...60 some bucks each for example. Balancing the reciprocating assembly and clearancing the block for the rod throws cost more than anything else.
Its pretty clear that its way way too much engine for that little truck though, so I'm looking for a stock 350 to put in it, and something more appropriate for this engine. I'm just stubborn about wanting to do it on the cheap. The truck its in now only set me back 300 bucks, with a barely running 2.8 in it. I tuned it up and drove it for 6 months on 5 1/2 cylinders before doing the swap rofl:
Kinda ugly underhood, but wasn't ever really meant to be pretty. Thats a full size suburban TBI air cleaner, trimmed to fit a carb airhorn, and the accessory bracketry is a factory 4.3 setup.
Still missing a volt gauge.
Chevelles and 60s/70's era platforms are just too expensive. Even the little 78-87 square body malibus are demanding a big price tag these days. I'm always looking for the older style s-10s with that in mind. Problem is, I need a clean short box 2 wheel drive body, and a short box 4 wheel drive frame, and the aforementioned AWD astro parts...to do what I have in mind.
Similar to one of these, but with a bunch more oomph:
CMD