McBroom
OBS Enthusiast
Awesome questionIsn't the pre-Vortec intake better? If so, can it be redrilled to fit Vortec heads?
The Blue Mule
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Awesome questionIsn't the pre-Vortec intake better? If so, can it be redrilled to fit Vortec heads?
Thanks for that handy info. I like the very detailed write up.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
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!
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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
Then will come the lift and 4.56 gears. Finished itll sit on in 37's
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.