This isn't 3rd gen related but SBC related. I recently got to take my SCSB '93 S10 w/ a stall TH350 and 3.73s for a few rips down the road. In 2nd gear from 2,000-4,000 RPM this thing feels a lot faster than I expected (it pulls way harder than my Z28 does in any gear at any RPM). I'm still not completely tuned and have yet to successfully lay into it in 1st gear or go above 4,000ish RPM without it blowing a collector gasket (2" dual pipes with shorties; ordered long tubes and a 2.5" dual exhaust). I took the exhaust off and left it open headers (2.5" collectors) and ran it to about 5,000 RPM in 2nd gear and instantly smiled from ear to ear. The tach shot up from 3,000 RPM, laid rubber and put my head into the back window.

Anyway the motor is a stock bore roller 350 with vortec heads, an XR276HR cam (224/230 duration .502"/.510" lift 110 LSA), 9.4:1 compression and roller rockers. The truck weighs in at around 2,700lbs and I was shooting for mid 12's. It feels significantly faster than my mid 13 second Z28 and my buddy's 12 second T/A. I originally figured it to be about 340 horse/close to 400 ft lbs but looking at the less aggressive LT4 hot cam (granted those are about 10.4:1 in LT1 motors) making an easy 380+ crank horse and feeling how this thing pulls, I'm starting to wonder if I'm pretty off with my estimate.

Any estimates?

 

Horsepower numbers are weird because if you're reading magazine engine dyno graphs, that's usually at the flywheel without accessories. If you're reading wheel hp dyno graphs, it's way different, and if you're talking about SAE Net (what manufacturers use) it's way different again because its with accessories numbers at the flywheel.

There's a guy here with an xr276 350 with Vortec heads and he's putting out roughly around 375hp going by weight and trap speed. LT4 hotcams are going to make 325-350ish hp depending on compression, intake system, etc. I'd imagine you're in the 360-375 range on the "sae net" scale. 290ish whp, and 400ish magazine article hp.

 

375 at the crank I'd say. What induction are you using?

 

RPM Air Gap.
Glad to hear all this though.

 

Getting magazine dyno HP in the car is not difficult or challenging, if you leave off the belt(s) when testing. Getting a HOT L31 to 350 HP isn't an accomplishment, it's a failure. I've seen one do 419 HP, live, in-person, with mufflers, alternator, and electric water pump. FelPro 1094 head gaskets, back-cut CP undercut valves. Headers were 1.625" long-tubes, intake was RPM AirGap, rockers were full-roller 1.5:1, carb was custom Demon 700, ignition was custom DUI. NO porting. Short-block assembly was used 91k-mile. In-car with 700R-4 was chassis-dynoed at 343 with drag radials and synthetics, using a TransGo kit in the trans, and a stock L98 'vette converter.

 

Well I think my goal is more than attainable going mid 12's in a 2,800lb truck with this setup. Probably should even be a bit faster than that. Hopefully I'll figure out my exhaust and get it down to the track for a few passes before they close.

 

That's not consistent with any of the numbers I've seen before. Its not a huge statistical outlier, but I dont think it's a realistic expectation that a vortec headed 350 is gonna hit 400hp nor do I think it's a failure to hit less than 400. The vast majority do not even with great supporting hardware. You are very limited to how big you can go on a cam with vortecs and still have a streetable car and power brakes. They dont respond to high lifts or high RPMs well and you hit a wall of diminishing returns quick with those two things in mind.

Not saying it didn't happen, but it's probably about the absolute peak of what Vortec heads can do on a perfectly set up, perfectly tuned 350, and that's assuming that chassis dyno is even accurate.