250hp from 4.3 chevy v6?

It can be done. Look into this guys site, lots of good reading.

http://harrishighperformance.com/

Got room for an inliner? The 4.2 Vortec pulls 270hp in stock trim.

This is a Challenge truck, right? My recipe would be to skip all the internal engine stuff. I'd be all over the suspension and weight balance to enable momentum through the autocross and feed it a bottle on the drag strip. Not as glamourous, but just as effective.

With your limitations I think it would be easier and cheaper to start looking at efi & forced induction with stand alone engine management. A properly sized single turbo would pep things up. Add a M90 and you would definitely have the feel of a V8. Properly matching the parts (turbo or SC) and with some tuning you could have a perfectly street-able / usable DD sleeper.

Competition Cams: Camshaft PN 18-119-4 (high-energy flat tappet)Lifters PN 812-12 , Timing chain set PN 3200,Rocker arms PN 1412-12, Push rods PN 7812-12, Valvesprings PN 980-12

This, in an X vin 4.3L block, W vin L35 vortec heads with porting done, and a 95-97 S10 SS MPI fuel injection intake(or carbed intake, my modified stock 98 intake was E36 M3ty for it), headers, free flowing exhaust and a decent tune should net you 250-260rwhp from a vortec.

My '98 had the whole list there sans the SS intake, but had a 7k rpm limit, and decked heads....but it put down 255rwhp n/a and 320ish on an 80hp dose of laughing gas.

The 4.3L isn't a bad engine, but you NEED to start with a block that doesn't have the balance shaft if you want to cam it.

Last time I priced rebuild kits for 4.3's they were twice the price of the SBC stuff (which made no sense to me since it's 3/4 of the same parts) but gaskets and such could be pretty expensive (for a chevy build).

so zombie thread has returned.

i did ALL the suspension work. 3/5 drop, tubular control arms, zq8 sways, 17x8 wheels with 245's all around. handled like it was glued to the ground. then i traded it to my buddy for a t56 for my belair.

so the original question is now moot. i do have another 4.3 vehicle but my easy cheap power is coming in the form of a v8 donor truck.

In reply to patgizz:

Get the truck back so the collective can get this worked out.

I remember when you listed that truck in the classifieds. It looked good and I really wanted to buy.

THE 4.3 is heavy. uber heavy. Cast iron block, cast iron heads. A modern Vortec (4.8/5.3) is going to be a few lbs lighter than the call iron 4.3 thanks to this modern metal called "aluminum" and plasic for the intake etc....

BUT, if you're set on the horrible sound 4.3, then cam, head work, bump the compression and you can go with the 454SS injectors and t/b with a custom prom should get you in the neighborhood of the 250hp. You're still going to have a lower rpm engine (5500-ish) that sounds horrific and makes mediocre power.

In reply to Bobzilla:

You can rev them, just don't expect them to last forever...they still sound horrible though.

I know.... I have had my share. I put dual 2.25" exhaust with dual cats/cherry bombs Y'd out at the back. Ran GREAT. Sounded like complete and utter E36 M3. The resonance that thing created at 70mph was like noise canceling headphones, only instead of making it seem quiet, it made everything really really loud.

<<<Straight pipes pwn joo......

Ya get that truck back so we can finish this thread LOL

Hot Rod magazine did what you're trying to do. Go here: http://www.hotrod.com/techarticles/engine/113_0208_chevy_43l_262ci_v6_engine_build/viewall.html

I know this is an old post but here's my two cents worth.We did the following a Blazer and were pleasantly surprised.

First: Balance the motor. It will take mallory metal and cost more but when done right, it will feel like you have a V-8.

Second: For TBI motors, Crane can grind you one of their Compu-Cams that are computer compatible. We used one and again, it felt like a V-8 under the hood.

Third: Pocket port the heads, zero deck the block. The first will help flow everywhere and the second will get compression up to the stated spec and help prevent detonation.

Don't expect miracles like 500 hp, but if you enjoy a smooth running, pretty decent accelerating motor this will do it. We didn't bother with headers because I hate exhaust leaks and if you have an exhaust leak it will mess with the O2 sensor.

We are going through my son's 4.3 hyd roller and using this formula again. I am looking forward to driving a fun little truck.

In reply to patgizz : 

You'll find the 4.3 doesn't weigh significantly less than the 5.7 If you use the ones with aluminum heads  it's probably lighter.  Toss a short body aluminum water pump on it and it will fit in the same space.  

Remarkably they both get about the same fuel mileage. The problem with the 4.3 is it's a 90 degree V not the ideal 60 degree. 90 degree V either needs a balance shaft or offset crankshaft. A 60 degree needs neither.  

Holy berkeleyballs zombie thread.  I've graduated to LS swapping everything 

In reply to frenchyd :

The ideal for a V6 is 120 degree, not 60 degree, but I think only Lancia ever made a 120 degree V6.  Difficult engine to package.

Any V6 that isn't 120 degree will require either an odd firing order or split crankpins.  Or, in the case of the 4.3, both: They have split crankpins, but they aren't split enough for an even firing order due to crank strength reasons, so it is a semi oddfire engine.  IIRC it is 108/132 degree firing intervals.

Because of the geometry, 90 degree V6s have lighter and stronger cranks than 60 degree.  90 degree have split crankpins, 60 degree are so wildly split that they look like 4 main inline-six cranks.

If using turbos 250hp for the 4.3 v6 is nothing. Gmc  made atleast 280 hp with the turbo 4.3 in the Syclones and Typhoons.

I would be hard pressed to go 4.3 anything when you can get a LM4. 
 

Now another direction that I think would be cool/fun is take one of the Mazda b series pickups and put a Mazda K series motor in it. Oh the sounds it would make.  I would not care what Hp/Torque numbers I was getting. 

Eh, I have a good 4.3 that will be reused in something else when that truck gets its v8 swap. I have no problem with 4.3s. In my case of having more engine bays than i have engines I certainly don't turn my nose up at it. I just put a limit on the amount of money i would spend trying to improve it. 

I played with these for a while swapped into a toyota hilux), at any meaningful power level I couldn't stop evenfire cranks from breaking constantly. Dont rev them and dont try to make big power.