High performance V6 4.3L

McBroom · Dec 29, 2019

Supercharged111 said:
Isn't the pre-Vortec intake better? If so, can it be redrilled to fit Vortec heads?

Awesome question

The Blue Mule

RI Chevy guy · Dec 29, 2019

I did a build up on my 4.3 and love it! That being said, mine is a '96 vortec, so quite a different animal. I did a basic port on the vortec heads (opened the bowls up, smoothed things out a bit and matched to the intake & headers, these heads breath pretty well already), upped the compression ratio a bit (went to 9.6:1, looking back would've upped it a bit more), Speed Pro rings and bearings, kept the stock injection set-up but had the throttle body ported and upgraded the injectors themselves to mpfi. Had the whole rotating assembly balanced: cannot overemphasize the importance of this step, these engines are known shakers and even with the balance shaft (which you probably don't have) balancing the cylinders is paramount, find a very good machine shop and get this done. Look to Comp Cams for the valve train, they have several grinds for these engines. Lunati also has offerings for these, but I can only speak to the Comp Cams components. I have a hyd. roller cam ground for use with computer controls (this is my daily driver and I have to be able to pass inspections), 266/270 durations, 112 LSA, ovate wire springs- which I really like, dual would springs tend to be a pain. Went a little crazy with the rockers: Comp Ultra Pro Magnums, went with these to eliminate the last real friction/heat area of the head, with full roller fulcrums and roller tips I have very little resistance in my valve train and no direct metal to metal wear that the stock rockers have. Another really important step: these engines have a non adjustable valve train. In short, you need to use the pushrod length to obtain proper valve train geometry; i.e. at zero lash, the rockers are contacting the face of the valve stems at center, being off one way or the other will dramatically accelerate the wear on the valve guides. Hope this helps, I spent a lot of extra money ensuring the durability and performance of this engine, and I have not been disappointed. But with that, this is a daily driver that will occasionally be used for more than it was designed for. It's a delicate balance of fuel economy and power and suits my needs perfectly. Now if I can just get the damn body work finished and painted! Good luck on your build

McBroom · Dec 29, 2019

RI Chevy guy said:
I did a build up on my 4.3 and love it! That being said, mine is a '96 vortec, so quite a different animal. I did a basic port on the vortec heads (opened the bowls up, smoothed things out a bit and matched to the intake & headers, these heads breath pretty well already), upped the compression ratio a bit (went to 9.6:1, looking back would've upped it a bit more), Speed Pro rings and bearings, kept the stock injection set-up but had the throttle body ported and upgraded the injectors themselves to mpfi. Had the whole rotating assembly balanced: cannot overemphasize the importance of this step, these engines are known shakers and even with the balance shaft (which you probably don't have) balancing the cylinders is paramount, find a very good machine shop and get this done. Look to Comp Cams for the valve train, they have several grinds for these engines. Lunati also has offerings for these, but I can only speak to the Comp Cams components. I have a hyd. roller cam ground for use with computer controls (this is my daily driver and I have to be able to pass inspections), 266/270 durations, 112 LSA, ovate wire springs- which I really like, dual would springs tend to be a pain. Went a little crazy with the rockers: Comp Ultra Pro Magnums, went with these to eliminate the last real friction/heat area of the head, with full roller fulcrums and roller tips I have very little resistance in my valve train and no direct metal to metal wear that the stock rockers have. Another really important step: these engines have a non adjustable valve train. In short, you need to use the pushrod length to obtain proper valve train geometry; i.e. at zero lash, the rockers are contacting the face of the valve stems at center, being off one way or the other will dramatically accelerate the wear on the valve guides. Hope this helps, I spent a lot of extra money ensuring the durability and performance of this engine, and I have not been disappointed. But with that, this is a daily driver that will occasionally be used for more than it was designed for. It's a delicate balance of fuel economy and power and suits my needs perfectly. Now if I can just get the damn body work finished and painted! Good luck on your build

Thanks for that handy info. I like the very detailed write up.
So in your opinion would I be better off with a: my non vortec b: a vortec or c: a marine block?
I've got a limited budget for this build. Are you running an automatic or manual transmission

The Blue Mule

DavidAlan · Dec 30, 2019

GM ,when they realized guys where beefing up the V-6,came out with there very own hot v6,so look in there performance section of GM,not sure if still made,also you could look at companies,like Jasper Engines and such about there tricks on beefing up a premade engine,so save you the hassle of your own mistakes,let them show you there fixes.
Good luck,on what you do.

L31MaxExpress · Dec 30, 2019

McBroom said:
I've got a 91 4x4 RCSB 4.3L 5 spd with somewhere in the neighborhood of 180K on the clock.
I know the 4.3 is basically a 5.7 that's missing 2 cylinders.
I'm planning to rebuild the engine and add a butt load of cool **** to it. I've found the majority of the parts that I wanna use. But, I'm not sure on a few things.
I've found these parts:
4 barrel Intake,Edelbrock carb(500cfm),headers,electronic ignition(complete msd).
I'm still looking for the cam.
As far as internals go every thing from a 5.7 will work
(valves,springs,rockers,pistons,rods...)
How much hp can I expect to gain over its basic 180hp?
I'm not interested in swapping to a V8!

Sent from my SM-G975U using Tapatalk

I think it would be cheaper just to buy a bone stock L31 from GM. Get a vortec carb manifold and a HEI. ~300 hp and 350 tq.

RI Chevy guy · Dec 30, 2019

McBroom said:
Thanks for that handy info. I like the very detailed write up.
So in your opinion would I be better off with a: my non vortec b: a vortec or c: a marine block?
I've got a limited budget for this build. Are you running an automatic or manual transmission

The Blue Mule

Tricky question. A lot depends on your skill set, budget, how much power you're trying to get out of it, and your access to a good machine shop. My instinct would be to build up what's there, swapping to a vortec would necessitate a full computer/harness swap- at that point you might as well go with an LS, all the little things that change from one engine to the next (brackets, sensors, wiring, etc.) can be the greatest headache of doing something like this, and getting things to work where something else should be doesn't always go as planned. Using your existing engine you could dismantle and send to the machine shop, figure out what components you want to use while your machinist checks everything over and get everything ordered for far less than a replacement engine, and you would have control over what is being done (and to what degree) to your engine as well as what parts are going into it. A guy doing a stock rebuild is going to cut corners where he can so he can; he won't be using moly rings or bearings, won't spend much time on the crank or rods, and you can almost rule out balancing. If you have the ability and the drive to do it (at the same time) I'd do what you can yourself, buy the parts you really want to put into it (think valve train), compromise where you have to and take your time. Oh, I'm running a slightly modified 4L60E

McBroom · Dec 30, 2019

I'm an outstanding mechanic built several drag cars and a couple of drift cars too. Planning and designing are fairly simple. Im a welder/fabricator as well. I've almost 45 years working on vehicles.
I grew up having to fix it Saturday so Daddy could go to work on Monday. Grew up poor but learned a lot. Am I the smartest by no means. Am I willing to learn new tricks? Hell yes!
I'm gonna squeeze every oz of power I can get out of it just short of a blower.
Then will come the lift and 4.56 gears. Finished itll sit on in 37's

Edit: it's a 5 speed manual

I also gotta KISS( keep it simple stupid)

The Blue Mule

letitsnow · Dec 30, 2019

McBroom said:
Then will come the lift and 4.56 gears. Finished itll sit on in 37's

I bought a new 1999 s10 zr2 back in '99. With the stock oem 31" tires, the vortec 4.3 was just adequate in that light s10.

USAF Long · Jan 9, 2020

Keep us posted. I wish I wouldn't have junked my old 4.3L I pulled out of my truck. I threw a rod through the oil pan. Should have kept the long block and rebuilt it.

Hipster · Jan 10, 2020

L31MaxExpress said:
I think it would be cheaper just to buy a bone stock L31 from GM. Get a vortec carb manifold and a HEI. ~300 hp and 350 tq.

Exactly

High performance V6 4.3L

McBroom

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RI Chevy guy

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McBroom

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DavidAlan

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L31MaxExpress

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RI Chevy guy

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McBroom

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letitsnow

I'm Awesome

USAF Long

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Hipster

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