WHAA stock 4.3 taking 8lbs os boost safely

[OneHung4.3]

Ok, I was sifting through some other sites and junk, came across some one scattering on about how an internaly stock 4.3 can take 8lbs of boost safely needing only a tune and some fuel mods? This true because I didn't think the 4.3 could take it without ripping out the inside and replacing with some forged pieces. I'de be weary about running 6lbs on my 4.3 let alone 8

[Justin_Inc]

just about any engine can handle up to 10lbs of boost as a general rule. Its honestly all in the tune and fueling. keep on the safe side and things will live a long and happy life.

[OneHung4.3]

Ahh, Thanks for the insight. I got to say this is the best forum for Chevy trucks. Great info and great people with straight answers. Been feathering the Idea of turboing my 4.3 ( All 8 of my cars I have owned have been turbo'd so it's nothing new to me ) Only one broken engine...sent a few pistons into orbit.
I just don't know really anything about the 4.3 or it's fuel system. Thanks to everyones great knowledge I have a better understanding.

Best way to get a good wholesome tune for the money is just finding a local shop with a dyno? I don't trust the over the internet or mail in tunes that much.

[89rcsb]

Yeah, grab something like HPTuner and go nuts at the local dyno shop.

BTW, the 4.3's fuel system is so crappy it's nauseating. Although, Mercury Marine sells an intake that has LT-1/LS-1 style injectors and is easily modified to support boost.

[Camet11]

just about any engine can handle up to 10lbs of boost as a general rule. Its honestly all in the tune and fueling. keep on the safe side and things will live a long and happy life.

I agree with this!

[OneHung4.3]

Awsome, I had the notion that a 4.3 could take a small dose of boost just didn't know how much. I have to agree, I had a chance to get to know the spider system junk and it does look a little nasuseating. The marine intake idea looks promising but a little pricey. I only plan to run 8lbs tops on a smaller sized turbo and can probly fab up a system at or around 1500.00 ( I have a bunch of extra and left over parts from previous projects laying around ) Doing a Marine swap looks a bit price for just 8lbs. Ihear the 36lb spider system from wynjammer is not to bad.
Not looking to add major power just a little in mid to upper range.
Ehh wonder how quickly a 4.3 would spool a itty bitty t25.
We'll see what I'll come up with in a week or so once this cold rainy weather leaves.

[6.0vortecchevy]

Once you start to really get into the meat and gravy of your truck this web site is lacking a bit.

[chevy4.3]

The stock internals of a 4.3 are supposed to be able to take 350 hp on the crank. 300hp/tq on stock internals is not a problem if done correctly. If you read or talk to the experts, they'll say that an increase above 50% of the original power output of the engine is seriously stressing it and will likely blow. This is why the 4.3 is a good candidate, it's built like a rock and will handle anything you throw at it...within reason. Trust me, you woudln't want to go boosting the average 350 75% above its current hp level.

There is more clamping force on the heads of these engines than the mains, so you're likely going to **** the crank through the mains or blow a rod/piston before you blow a head gasket, but anything's possible -->This statement is different with a high mileage engine or a hard/bad running engine.

I believe you have 19#hr injectors stock, with a very inefficient spider setup. This is the first thing limiting your engine, it needs to go unless you plan on running only wet nitrous (which is a whole nother topic). I wouldn't trust a modified spider system on boost either, wynjammer sells one. It's not worth it. With a marine intake swap and 44#/hr injectors you can max out the potential of your engine (also would need a tune or adjustable fuel pressure regulator, 255#hr walbro fuel pump or higher equivalent).

The way power is built through the rpm range is going to blow the engine, not the amount of power added. So boost numbers for max hp/efficiency are completely irrelevant unless tuning yourself. I understand there are a lot of paramaters you can adjust when tuning with hp tuners or something, but you're not going to get the most out of the setup. No sense in spending 1000$+ on s/c or turbo to end up with a 40-60 hp gain. Have it dyno tuned for real, and safe, results.

About the boost- I don't believe anyone makes a roots/twin screw type kit for the 4.3. This is because the engine would likely blow on very low boost. A turbo is a little more efficient than centrifugal s/c (if you were to compare these two). My guess is you could only run about 10psi off a decent sized turbo, but there are a million other variables. You should be able to run 12psi off a centrifugal s/c when done correctly.

two things to take into account - intake charge temp. and timing. The rule of thumb is around 5-6 psi is as much as you can go without intercooling or meth injection-- on the stock fuel system. I prefer meth injection with the 4.3 cuz it's simpler. I would not use meth injection on an everyday-driver engine which is going to be in boost at low rpms (i.e. roots type). This is the beauty of a turbo or centr. s/c Most are programmed (on stock internals) to boost a few psi, say 2-4psi, at 3000rpms then increase to whatever max boost at redline. That means at normal driving speeds(under 2500rpms) there is no performance enhancer which is good, no added stress on the engine. When that intake charge becomes hot after around 6 psi you start to lose power. This is why you see guys running insane boost and actually increase an ET when the boost is lowered a little (also traction issues).

Timing goes without saying, if you're running any supercharger on any stock internals without carefully mapping out and retarding the timing, then you might as well drill a hole in a freeze plug and drive around for a few days.

Other things to consider - crank bearings will wear quickly on any stock engine that's had as much as 50% power added. This could decrease engine life(and power level) every time you smash the throttle. Also expect the main caps to walk when you get to power levels near 350hp/tq for extended periods of time. The motor mounts for these engines are weak from what I've heard. Boost is also going to appreciate a cam with less overlap-- this allows the intake charge to be held in cylinder for a split second longer and you get more out of your charge of air/fuel that way. If you wanted real results, at least replace bearings/main bolts to studs/motor mounts/cam swap. But that's not necessary.

If you decide to boost, the good thing is you don't need better flowing heads for power levels we're talking about with the 4.3. If you wanted to be safe, stick with a more restrictive exhaust (stock manifolds and cat-back setup). A very efficient open exhaust for a naturally aspirated engine won't perform the same on a lightly boosted 4.3 ->you'll need some restriction/backpressure.

The last thing I'd say is this - if you plan to use your v6 truck as a truck, then don't boost. If its a street machine go ahead. The amount of power gained on 6psi isn't worth the investment. And above that power level you start to put serious strain on the engine under boost when you are pulling a trailer or have maxed out your payload for a job or something. S/c or turbo on stock internals - pretend it's nitrous and use sparingly. You wouldn't spray a 75 shot of nos pulling a boat...at least I hope not