400hp 350 Vortec?

[slowburb]

The problem with TBI is you cant get enough air in the engine. The heads are restrictive and doesn't respond well with a bigger cam. You cant get a 4bbl TBI. That's why a lot of people got a set of after-market heads, dual plane intake and 4bbl carb. This setup with a like Holly sniper EFI would be awesome. a good set of heads makes the engine. A cam refines it. Engine masters did a segment on home porting heads as well. There is such thing as too big of a head. note: This really needs to be in a post on its own. when your port intake gets so large that the velocity lowers to where the fuel and air don't mix well. This means not enough bottom end. The way the car makers makes emissions is restricting the engine enough to lower emissions. When you open it all up and gain peak performance from your stock bottom end your emissions goes to crap and your econ goes up. Basically uses less fuel but not burning all the fuel mixture. So if the OP can find vortec heads, cheep duel plane and add the 4bbl TBI and he will get better performance and fuel econ. He would just have to keep it for a long time to reap the benefits.

Right. So it's not all that practical for someone looking to build up their TBI engine without all the hassle of swapping to carb and distributor. Ultimate TBI mods and the quarter trick may help some. The bigblock TBI may help some but I think this power level on a TBI truck will require fueling mods, possibly to the extent of a better pump and vacuum referenced fuel pressure regulator. It's not like you could just slap on an aftermarket EFI and go.

Yes, the heads are the key, and the cam is matched to the heads. I'm not sure there was much gain in the video from the upgrade from 1.94" to 2.02" intake valves. For the most part, it's BEST to leave the intake tract of the vortecs ALONE. A bigger valve without supporting chamber and port mods would change atomization characteristics and port velocity. I chose NOT to install bigger valves in my vortecs for this purpose. It's known that the L31 intake manifold is the bottleneck in the induction system, so I had no problem porting it out for a few more RPMs, and have no problem recommending this to anyone else who is hopping up an L31.

I'm leaving your emissions remarks alone.

Because if I am going to have my engine completely torn apart for a rebuild why only gain 45 ft lbs? Being a truck motor it will still make more torque than horsepower. Thus if I am making 400 hp then I should (in theory) make over 400 ft lbs. After all there is like a 100 number difference between the stock outputs. I believe our computers are different? Being that mine is a 1998 and yours is 1996? I'm not sure as to what the differences are but I know that HP Tuners can't be used on 1997 and older Vortec's


Interesting. Granted I am only running at around the 4500 lbs mark with my truck being a regular cab step side 4x4. Fast enough to keep up with (if not out run) my buddies 6.0L LS k20 haha

OK, then build it for as much TORQUE as possible and let the HP be as it may. Unless you ditch the black box and the intake manifold/CPI/CSFI/MPFI, you're not going to be able to spin it or feed it fuel for much more than 400 horses. Otherwise you're in a set of $1600/pair AFR 190 heads and a cruddy iron intake, or $1000+ marine intake, or $2500+ ramjet or aftermarket setup.

You realize that HP is a function of torque at given RPM, right? And that your engine is SEVERELY RPM-limited, right?

Let's get real, if you want that kind of power and want it to make sense, you need to call the old dude at wynjammer and order up a walbro pump, a hot hi-flow spider set, a black box, and a procharger.

Either way you'll be posting about where to get a beefed up transmission soon enough (because you'll blow yours to smitherines).

 

[minicooperzoom]

OK, then build it for as much TORQUE as possible and let the HP be as it may. Unless you ditch the black box and the intake manifold/CPI/CSFI/MPFI, you're not going to be able to spin it or feed it fuel for much more than 400 horses. Otherwise you're in a set of $1600/pair AFR 190 heads and a cruddy iron intake, or $1000+ marine intake, or $2500+ ramjet or aftermarket setup.

You realize that HP is a function of torque at given RPM, right? And that your engine is SEVERELY RPM-limited, right?

Let's get real, if you want that kind of power and want it to make sense, you need to call the old dude at wynjammer and order up a walbro pump, a hot hi-flow spider set, a black box, and a procharger.

Either way you'll be posting about where to get a beefed up transmission soon enough (because you'll blow yours to smitherines).

Yes I know horsepower is derived from torque and that there are massive RPM limitations. But I’m not trying to build a 7K RPM SBC. I want a nice street motor that’s got a nice lope at idle and makes pretty good horsepower and torque. So I’d happy if it made over 325hp and somewhere around (if not above) 420 ft lbs. I just choose 400hp because it’s a nice round number and why not shoot for the moon? Haha. I know the 4L60E isn’t exactly the strongest trans out there either.

 

[slowburb]

Yes I know horsepower is derived from torque and that there are massive RPM limitations. But I’m not trying to build a 7K RPM SBC. I want a nice street motor that’s got a nice lope at idle and makes pretty good horsepower and torque. So I’d happy if it made over 325hp and somewhere around (if not above) 420 ft lbs. I just choose 400hp because it’s a nice round number and why not shoot for the moon? Haha. I know the 4L60E isn’t exactly the strongest trans out there either.

Nice street motor
Nice lope at idle
Pretty good HP & TQ
You're asking for too much.

 

[Christian Steffen]

For the money you would probably have in the 350 to get close to 400 hp, you could probably buy a decent used vortec 7.4 and 4l80e. Swap those in and get a tune from blackbear or someone else that does mail order tunes. You won't blow up the transmission and you'll have a ton of torque.

Disclaimer: I don't know how well a 454 and 4l80e fit in a regular cab half ton.

Edit: Just throwing ideas out there. I know someone else suggested ls swap earlier, but I figured there would be more compatible parts with the same era 7.4.

 

[minicooperzoom]

Nice street motor
Nice lope at idle
Pretty good HP & TQ
You're asking for too much.

Well... I know compromises will have to be made somewhere and that will probably be in the power department.

For the money you would probably have in the 350 to get close to 400 hp, you could probably buy a decent used vortec 7.4 and 4l80e. Swap those in and get a tune from blackbear or someone else that does mail order tunes. You won't blow up the transmission and you'll have a ton of torque.

Disclaimer: I don't know how well a 454 and 4l80e fit in a regular cab half ton.

I do like the idea of a BBC seeing as how my fuel economy can't really get much worse (I avg. 10 mpg) and the ability to make power is a lot easier. I imagine it would fit fine? Aren't all the trans tunnels and engine bays the same size between 1500's, 2500's, and 3500's?

 

[Christian Steffen]

Well... I know compromises will have to be made somewhere and that will probably be in the power department.


I do like the idea of a BBC seeing as how my fuel economy can't really get much worse (I avg. 10 mpg) and the ability to make power is a lot easier. I imagine it would fit fine? Aren't all the trans tunnels and engine bays the same size between 1500's, 2500's, and 3500's?

I'm not sure. I've never owned a 1500. If you had some areas you were concerned about, I could take some measurements off of my truck.

And exactly, greater power potential with fewer mods. Probably the first limiting factor you'll run into is the stock injectors, they're just not big enough. But if you were getting a tune anyway, you could run something like ls1 injectors.

I would expect better than 10 if you only way 4800 lbs. I usually get 12-13 daily driving my truck, and 14-15 on longer drives.

 

[Biggershaft96]

Body panels, beds , cabs are all identical from a 1/2 ton to 1 ton. Daves buddy swapped a 3 door cab from a half ton onto a 1ton 454 nv4500 truck.

 

[Tavi]

I agree with the big block swap.

The lope you’re hearing is the sound of the engine running like crap at low RPM. A looser stall allows it to wind up into its power band before a real load is placed on the engine. A higher stall can tame the engines Street manors at the expense of heat in the transmission.

Robbing a bit of torque from a big block isn’t as detrimental as from a small block.

 

[Blackwater]

For the money you would probably have in the 350 to get close to 400 hp, you could probably buy a decent used vortec 7.4 and 4l80e. Swap those in and get a tune from blackbear or someone else that does mail order tunes. You won't blow up the transmission and you'll have a ton of torque.

Disclaimer: I don't know how well a 454 and 4l80e fit in a regular cab half ton.

Edit: Just throwing ideas out there. I know someone else suggested ls swap earlier, but I figured there would be more compatible parts with the same era 7.4.

The 454 will fit. they made all the bodies the same.

I mentioned the LS swap earlier because of less cost and easy HP gain. I also mentioned slapping vortec heads, dual plane intake, sniper EFI 4bbl and a cam. Future reference, I will not suggest a carb unless the OP wants to keep a pre 87 truck setup. You will need a carb intake for the aftermarket TBI systems to work since the original TBI is 2bbl.

 

[shovelbill]

good morning,

i know i read like an ass with my post, it was one of those days.....actually because of a customer i had that wanted a "unicorn" motor with a donkey wallet.

i spend most of my time at a Harley stealership building engines and combos for people that usually don't know what they want to begin with........and lots of the problems is because they read forums and see dyno sheets....."well BOB123 said he heard, blablabla and JOE678 did blablabla"....and everyone wants to have paper to brag with. problem with that is the GOOD builds cost 2-3 times what my customer's budgets are and they were built for big #'s by world class tuners.....not always for the perfect combo in mind.....ie: longevity........i tell them all that i ride a bike and not a dyno.....some look at me funny too.

i sorta blew the L31 in my truck when the oil pump went.....there's some threads and crap on that and then my blown 4L60E too......anyway.....after thinking, pondering and more thinking on what i really needed vs. what i wanted i decided my best bang for MY buck was a GM HT383E.......after i got that, i wiped my transmission(line blew off)......

bottom line is i put in crate engine, Volant cold air, JBA ceramic shorties(with EGR), Magnaflow high flow cats and the JBA single sided CAT back setup.....then i got a crate GM 4L70E trans, which is rated for 495 LB FT.....and a custom Hughes torque converter to go with my 3:42's

the stock 1998 computer will run it.....with stock intake and exhaust the engine is rated for 323/444........and will make more power with a proper tune......and i'll hazard a guess a lot more with a better than stock airbox and exhaust.

http://www.chevrolet.com/performance/crate-engines/small-block-ht-383e
http://www.jegs.com/p/Chevrolet-Per...ruck-383ci-323HP-Crate-Engine/764049/10002/-1

the truck was used as a daily for 6 months before i bought a little Ford Focus to save money on gas on days i couldn't ride my bikes.........i was doing 112 miles round trip to work........the end result was 13 combined MPG and i consistently got 15.8 MPG on the interstate at 68 MPH.......mileage dropped considerable at 75 mph.

this isn't my first rodeo on this topic.....i have a bunch of threads about my truck and lots of stuff on Harley builds on here.....search my posts (if you can get past all the headlight stuff)

i'm not a car/truck engine guy......i'm a Harley engine guy.......motors run on math and all the principle apply across the board. you need to build a proper COMBO for it to work in YOUR application.......heads, cams, gearing, weight, riding style, geography and elevation all play into it......mismatched **** gets you expensive garbage.

hope this helps a bit.