Potential Build, Destroked Aluminum 5.3 to 4.8, IR Intake, 8500 RPM

[theastronaut]

I'm in the planning stages for an engine for my '66 daily driver/mild pro-touring build. I know little about building LSx engines, though I've worked with hi-po aircooled VW engines for awhile. I've been thinking about building a 4.8 using an aluminum 5.3 block for better mileage, and also the crank would be stronger due to more rod journal overlap. The truck will be used as a daily driver, and run at open track days, and the occassional autocross. I'm not wanting to compete with it, just want to get it out on the track and have fun. I'm planning on using an individual runner intake with four 2 barrel Dellorto or Weber carbs for the intake. I haven't decided whether I'll use downdraft or sidedraft carbs/intake yet. IR intakes broaden the powerband, and tames big cams since they eliminate reversion problems that plenum type intakes have. I'd like it to rev to around 8500 rpm, and make good power to around 7500 rpm. I think the broad powerband that the IR intake offers would be great especially for autocrossing where you're usually stuck in a single gear the whole run.

I have experience with Dellorto carbs on IR intakes; I use them on my daily driver VW. They're extremely driveable and make a ton more average power than plenum manifold systems do. My old stock engine'd VW daily driver went from getting 24 mpg hwy to averaging 32-34 mpg mixed city/highway, with a peak of 36.25 mph hwy, so they're not as radical as they look. I can use MSD for the ignition, use a wideband AFR gauge and tune it myself just like I have with my VW.


Here's what I'm planning so far, let me know what you think! Like I said, no previous experience with LS engines, so I don't know what heads/cam/valvetrain I'd need.

Aluminum block 5.3 (Less weight on nose of truck = better handling)
4.8 crank and rod length.
Forged rods.
Forged Pistons.
IR intake.
Four two barrel Dellorto or Weber carbs.