While I am not a big fan of the GM 4.3L V6 engine. There are some things you can do to improve on it. I hope you find the information below helpful.
1. The cam in the TBI engine is just plain AWFUL. Specs on Stock TBI cam is .050″ tappet lift (intake/exhaust) is 179/194; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is .350/.384. or at least I know its pretty close to the same as the crappy cam in the v8s. Valve springs are also VERY important due to the stock ones having a redline of 4500 rpm. With the proper cam and springs the redline can easily reach 6000rpm. Intake and cam is worth a good 40hp as long as you did the other mods too. I have listed a bunch of new cams at the bottom of the page. This should provide you with a sufficient assortment of cams for whatever power range you want for your motor. If you still don’t know what cam to use, email me at firstname.lastname@example.org all of your engine and vehicle details and I will gladly recommend a cam for you.
2. www.tbi-superchargers.com have a nice little supercharger kit that is reasonably priced and will give you V8 power from your little V6.
3. Heads, vortec 4.3L heads are cheap and easy to come by but it does take a little modifcation to make them work with TBI but its worth the effort. This modification does typically require changing to the 350 5235206 truck injectors
4. The air cleaner. http://www.thirdgen.org/newdesign/tech/ultimatetbi.shtml The baffle on the TBI Truck is too small for a 2.8L V6 much less a 5.7L V8. Or you can run with a 3″ tall 14″ diameter open element filter with a flat base. Also toss the choke collar,if you run the open element filter with flat base, that is between the TBI and the air cleaner assembly. Good for around 10hp
Here are the summit racing air filters that I use and recommend.
SUM-239421 14 in. diameter, chrome, flat base, 2in. element, air cleaner assembly for tight clearance hoods
SUM-239431 14 in. diameter, chrome, flat base, 3in. element, air cleaner assembly
Now open elements are NOT really recommended for 4×4’s (water holes can drown that open element filter assembly) or you may want to spend a little more money for colder air for more power gains. If either is the case then you need the Hypertech CFM Powercharger and modify the base of your factory air cleaner to get more air to that throttle body. Also some nice cheap $60 cold air intake kits for TBI listed on ebay as well.
5. Modify the throttle body. This one pretty cheap but does require removing the throttle body. Ultimate mods . Good for few horsepower but not earth shattering but helps with the more mods that you make.
6. REPLACE that power sucking mechanical fan with dual electric radiator fans. That just kills the performance of the 4.3L and has a noticeable affect on the V8 engines as well. I have a webpage set up for this fan conversion.
7. The chip. Depending on how many of these modifications you do the more the need for a custom chip or chips. But a chip will give you the most bang for the buck of any mod you can do to the vehicle.
8. The exhaust on the 4.3L was designed to be used with the V8’s as well so it will primarily flow fine for anything your going to do with the 4.3L so I don’t recommend messing with the exhaust at all.
9. Underdrive crank pulley. Will take some searching on the summit racing website because not every year 4.3L used the same pulley like the V8 trucks did. Turning those accessories takes power and if you go with 25% underdrive on the pulley that is 25% more of that power going to turning rear tires instead of accessories and while that may not be a huge power gain but your truck needs a certain amount of horsepower just to move the vehicle at steady speed. If we can redirect some of that power from turning accessories to help maintain that speed.
So how much power can you make with a 4.3L. About 250hp with the vortec heads, a good cam and the the above recommended modifications. With a supercharger too its about 320hp.
On the 4.3L cams you will need to know if your engine has the balance shaft or not but here is the recommended 4.3L cam list.