It's in the June 2005 issue of Hot Rod magazine, on page 108. It's on the Chevy I-6's, not the GMC's. But I wonder if they might carry stuff to hop up GMC's too.
The biggest thing is, they used Chevy big block V8 long rods, for a tall deck. Then they used some kind of a Chevy aluminum piston and overbored the I-6 to that size. This significantly strengthened the rotating assembly to allow for higher rpms safely.
The next big thing they did was to either port the lump port stock heads, or replace the head with a modern redesign in aluminum, with beautiful direct port paths and heart shaped combustion chambers for high swirl and improved compression ratio.
The most powerful I-6's were either the port fuel injection engines or the one carbureted engine that had a custom intake fabricated. The Clifford 4bbl intakes were only good to 4800 rpm before they fall on their face.
With EFI or the custom intake, these things were pulling hard to almost 6000 rpm before they were done!!!
There was a 292 that snagged around 300 hp, and then a 250 that had just a little over 300 hp, but a little less torque than the 292.
And then at the end of the article they talk about having a turbocharged fuel injected I-6 being developed.
Wow, can you imagine a 400+ horsepower I-6? How cool is that?
I've gotta tell ya, I like the V8 converted Stovebolt trucks a lot, but with these kind of power options, it would make me think twice. If I could spin the motor to 6000 rpm and have a big turbocharger shove me hard into my seat with an inline 6, I'd consider it seriously over the hassles of a V8 conversion.
They didn't talk price. I'll look into that and post back here. That's the other thing. How comparable is it to building and converting to a V8?
