250hp from 4.3 chevy v6?

so my most likely $2013 candidate is my 1991 sonoma short bed regular cab 4.3 pickup.

i really do not want to toss more weight on the front of the truck with a v8 swap.

i just want a nice street friendly 250hp and close to 300 torques out of a 4.3 v6.

the truck has a 160/230 hp/tq(everyone's favorite measurement) TBI 4.3 with 183k miles and is very peppy but not enough.

i have a 190hp/250tq 1996 4.3 vortec engine that can donate parts for rebuild. has new heads but has a rod knock from abrupt stoppage when the timing chain broke and locked everything solid immediately. it bent a bunch of valves so i put on new heads and new timing set, and it had a knock so i pulled it and stuffed it in the corner. i do not desire to use the 96 block because of the extra mass and complexity of the balance shaft.

i would like to stick with TBI which puts me in an edelbrock intake made for the 4.3 vortec heads and an adapter(have adapter). the plan is for some sort of aftermarket cam and some true long tube headers. the factory cam is weak but is a hydraulic roller so i do not need retrofit roller parts, just a good cam and 3/4 of the new set of roller lifters i have sitting around for a small block. i am not opposed to going old school HEI distributor and carb but prefer to keep the TBI and just tune the computer since i have a program for that and chip burning cable/socket.

does anyone have some input good, bad, or otherwise? i looked on the s10 forum and did a google search and all i got was "holy crap you're not getting 250hp from a 4.3 n/a you need a s/c or turbo or nausssssss" i think that's a load of BS, and i believe i would be very happy with that power level in a sub 3000# truck. i don't need to run 12's i just want to be quicker out of the corners and have a little more to play with on the street.

this thread may devolve into my build thread once i tear the suspension off, which hopefully is this weekend.

I know a little (but not much about GM's 4.3)

I know the higher output models had vortec heads...

I also know put a turbo on there to pull off 280/360 hp/tq

also want to say there was a centrifcul (sp?) SC kit for it with the TBI setup

was just looking at cams, the edelbrock performer plus hydraulic roller has .479/.481 lift and apparently LS6 valve springs can be used on unmodified vortec heads to increase valve lift capability to .550 with no seat modifications.

i do not wish to go wild on the cam and make it sound crazy just "because racecar" at the loss of bottom end torque, as i will be loading the bed and using it as a real truck and pulling a small trailer

any sort of forced induction is out of the question for me both for challenge budget reasons and for personal budget reasons.

... another thought... could try a rear mounted turbo... http://www.performancetrucks.net/forums/forced-induction-159/remote-mounted-turbo-bed-456090/

sorry missed your post before I posted that last one ;-)...

i like boost so thats what I dream about

Some (other) auto mag that covers hot rods did a 4.3 build not long ago, their target was 300hp and i think they made it. Typical small block recipe, big roller cam, tall intake, carb, etc. bigger than challenge budget though, but it's possible.

save yourself the headache and just swap a 350 in there.. get rid of useless stuff from the front end like air conditioning and put the battery out back and your final weight balance will be pretty close to what you had with the 4.3.

duetto_67 wrote: Some (other) auto mag that covers hot rods did a 4.3 build not long ago, their target was 300hp and i think they made it. Typical small block recipe, big roller cam, tall intake, carb, etc. bigger than challenge budget though, but it's possible.

Dang, beat me to it. HRM did it a few years back. Forgot it was carbed.

In the ASA AC Delco series they got around 500 hp out of these with the racing cyl heads, high compression, big cam etc.

I would think that 250 at the flywheel would be easily accomplished.

I think the carb version would make more power for sure.

Aren't the heads on those pretty awful? How much room do you have in the budget for engine work?

Bore it 0.030" over, add a cam, rockers, bigger valves port the heads and see what you get?

Hot Rod did a 500hp build.

The HRM article stated that the best heads are the later Vortecs, they're kind of junk but they're the best stock head to work with and can use help from a grinder. I think they used aftermarket pistons to try and up the compression and it was indeed carbed. 300hp and it wasn't a smooth reving thing. There's headers and some other stuff. No big cams off the shelf that I remember.

novaderrik wrote: save yourself the headache and just swap a 350 in there.. get rid of useless stuff from the front end like air conditioning and put the battery out back and your final weight balance will be pretty close to what you had with the 4.3.

yeah thanks that is exactly what i asked for...

everything i own has a v8 something needs to be different. plus if i ditch the AC and move the battery back i'm even better off.

i have a tbi 350 on the stand. what is it, 210hp? yippee.

it's unfortunate the vortec 4.3 heads do not mimic the infinite awesome of the vortec 350 heads. maybe i shouldnt bother touching the engine until it blows up and by then have found a deal on an all aluminum 5.3

How about some high compression pistons and running E85? You could do that on a challenge budget since they are SBC pieces and you could run some super 13:1 or something depending on cam and make a bunch of power and torque together.

I'd say the typical small block stuff, plus ported heads etc etc.

If you can maybe work out some carpentry work in exchange for some machine work, mill the heads, deck the block and bring the compression up some.

patgizz wrote:

novaderrik wrote: save yourself the headache and just swap a 350 in there.. get rid of useless stuff from the front end like air conditioning and put the battery out back and your final weight balance will be pretty close to what you had with the 4.3.

yeah thanks that is exactly what i asked for... everything i own has a v8 something needs to be different. plus if i ditch the AC and move the battery back i'm even better off. i have a tbi 350 on the stand. what is it, 210hp? yippee. it's unfortunate the vortec 4.3 heads do not mimic the infinite awesome of the vortec 350 heads. maybe i shouldnt bother touching the engine until it blows up and by then have found a deal on an all aluminum 5.3

fine.. be that way..

there is a reason no one builds hi performance 4.3's that don't have a blower or turbo- they are a horrible engine for that. GM only ever felt the need to put out a hi performance version of that engine for 2 years and in 2 trucks- the Syclone and Typhoon- and they only got power out of them thanks to the turbo, liquid to air intercooler, and multiport efi.

pretty much any 350 will meet your performance goals with nothing more than a cam ($50, plus another $36 for lifters), valvespring ($50) and intake ($110) swap and a set of headers ($150) with good exhaust ($200 at most). all the time, aggravation, and money spent trying to get a 4.3 to act like a mild 350 could be better spent on dialing in a 350 and setting the truck up for it.

I'm not sure about other years/manufacurers, but in 1988 OMC had a marine version rated at 205hp with a 4bbl, 185hp with a 2 bbl.

That is with exhaust manifold, risers, and through prop exhaust.

I would expect a similar setup using headers, cold air intake, and aggressive timing and jetting would get you real close to 250hp.

Joe

You can certainly do it, but it's a PITA without boost. The only way you can get enough fuel in there is either a carburetor or multiport fuel injection (TBI never came with big enough injectors for that kind of power without upping fuel pressure, which has problems as well). Correction: you can use those huge 4 port TBIs from Holley, but their controller is horribly rudimentary, so maybe better to use it with a Megasquirt or something. The only way you can get MPFI is either the Sy/Ty intakes ($$$), marine intakes (weight!), Holley Commander intake (super rare and hard to find), or DIY modifications adding injector bungs to a carb'd aftermarket intake. So, let's just say you are cool with one of those options, and you can get enough fuel in there.

Now you need air. The 4.3 heads always sucked, even the "Vortec" heads aren't anywhere close to the V8 stuff...and they STILL sell that engine with the same junk heads!!! Assuming you're running a decent intake and throttle body (from above options), headers, and aftermarket bump stick, that still leaves the heads. A few options here. Vortec heads with mildest of porting (gasket matching) and a gnarly cam will get your power, but as you said you'll make some bottom end sacrifice. Do some major port work with the Vortec heads and you can run a less weird cam and hit your target IF you get it really well dialed in. The easiest, but priciest, option is to get GMPP/aftermarket heads from the Busch series days...aluminum heads with awesome flow made for roundy round racers, but those require special intake/exhaust/pushrods/cams. The parts are out there, tough to find but not impossible, but they still go for a LOT of money for what they are. These heads are capable of getting you way past your target, but of course that is getting into expensive territory and overkill.

So, with all that said, cam, ported heads, header, fuel+intake, and of course lots of tuning make it possible to hit your target. Assuming a DIY port job, you're still going to have a lot of money sunk into that cast block+cast head combo to avoid "adding" weight with a V8. I love the 4.3 and they're uber reliable and cheap, but if you look at the value proposition an aluminum 5.3 would be soooo much easier to get a good balance of value, performance, and weight. I've spent a lot of time fooling around with the 4.3 plans for my VW Bug, but it's simple fact that the lack of decent heads and all cast block and heads just kills the fun factor of the engine. Heck, the latest 60° V6 pushrod engines can hit your target power easily with much less weight, easier packaging, cheaper parts, etc.

Good luck.

Bryce

Have you considered E36 M3-canning the 4.3 and using the ultra cheap and much better 3.8 with 5 speed out of a crashed Camaro/Fireturd? An NA series II 3.8 will make 205 hp right out of the box and is MUCH lighter than the 4.3. The factory superchargers bolt right on too.

Don't like the weight of the 350?

5.0?

Why dont you just try to find a 4.3 turbo vortec out of a syclone theyre everywhere and those engines have 285hp and 350tq it wouldnt take much more to get to your 300hp goal, but if you get that you probably have to find a tranny that hold up with almost 400 lbs/tq

Knurled wrote: Hot Rod did a 500hp build.

yes but they killed it on the dyno, but it is possible. They have hinted about doing it again not on a budget since they had to cut corners because of the budget.

If you want to keep the TBI, you can step up to a 454 TBI, which has 2" bores and larger injectors. That will get you 670 cfm of airflow. With a cam swap and some head porting you should be able to get the 250 hp goal. A V8 would get you more of course, but nothing wrong with trying it with the 4.3.

Here is a Hot Rod build of a 4.3 that made 301 hp, so it is possible. http://www.hotrod.com/techarticles/engine/113_0208_chevy_43l_262ci_v6_engine_build/viewall.html

DaewooOfDeath wrote: Have you considered E36 M3-canning the 4.3 and using the ultra cheap and much better 3.8 with 5 speed out of a crashed Camaro/Fireturd? An NA series II 3.8 will make 205 hp right out of the box and is MUCH lighter than the 4.3. The factory superchargers bolt right on too.

It doesn't look the 3800 is much lighter per google search. The Supercharged 3800 is approx 450 lbs while the NA 4.3 is approx 400 lbs, so without the supercharger they are probably similar in weight. Which makes sense as they both have iron blocks and heads.

The 4.3 in my Astro is listed at 190 or 200 HP. That's with the stock intake and exhaust systems. How much more could you expect with headers,free flow exhaust and a cold air intake? Since we're talking about a Challenge vehicle you could look at some home grown head work maybe. They're not an exciting engine, but they are dependable. My last one had 265K on it without anything more than a water pump and a set of plugs and wires.