Extra hp out of my 340.

hux340 said
G'day All,
Thanks very much for your comments. I live in the country so the car does a bit of driving at 100k/hr. That's what's good about the 3.23 diff ratio. I don't think one jump up to 3.55 I wouldn't notice. I think the next size up is 3.7's. Would that make a diff off the mark with the below mods. Don't really want to touch the motor so I'll probably just go extractors & alloy inlet manifold for now, then some alloy heads later. Also the 340 had a HP Holley DP on it when I bought it. Made the mistake & took it off & put on a 680 Holley vac sec street avenger. I'll be putting the DP back on as it made the motor that bit more responsive. Don't care about burning more whole $$ as I only do about 5000 km's a year in the Demon. At the end of the day would like to get 400hp at the fly.
Cheers,
Glenn.

that's what some people say, but it's 9.9%! And it starts at zero mph and continues until you run out of revs or speed. It fattens up your on-road power right from the time you slip the clutch out. It's similar to having 10% more power, or a 10% bigger engine.
But I totally get the attractiveness of the 3.23s at hiway speed. I drove thousands of miles with 3.55s and small tires, at 65=3000rpm. Overdrive is better, at 65=2240rpm .
The headers are a good choice, as they too can fatten up the entire rev range.
The intake is more of a tuning tool. You can get them to change the powerband, or move it, and they work best when matched to the cam.