Thread: 4.3 v6

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i gotta 79MGB with a 94 4.3 v6 and a 700R,im trying to find out if the vortec heads from a 96 4.3 will bolt up to my 94.the dang thing runs like a scalded dawg

I don't see why they wouldn't. I believe they are the same heads. As for as I know they didn't rework them heads like they did the 5.7 heads. The vortec came from the fuel injection set-up.
But don't hold to this because I'm not 100% sure.

It's not an uncommon swap for 4.3 SyTy owners, to use the Vortec heads. But you need to search for the threads on their web sites (S10 pickup forums, SyTy forums) to see what's involved (heads + intake manifold).

I will add that the stock heads on your LB4 are the same swirl port type used on LO3 and LO5 sbc v8 engines. In all three cases, the heads can be ported to give results on-par with the Vortecs. See HRM's article on a 4.3 buildup they did:

http://www.hotrod.com/techarticles/e..._v6/index.html

http://www.hotrod.com/techarticles/e...v6/index1.html

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EDIT: IIRC the 96+ heads have raised port intake runners and heart-shaped combustion chambers, just like the L31 Vortec heads. The heads preceding these (yearwise) are called vortex by GM but what that really means is swirl inlet runner, or swirl port runner // swirl port heads, so they are effectively the same as the LO3 heads on a 305, or the LO5 heads on a 350.

The term vortec comes from vortex which is a rotating fluid flow. The fluid (air+fuel) rotation helps make a better/faster burn in the cylinder so less ignition advance is needed, and therefore less "negative torque" is made by the engine (ignite later but burn faster = more power). The tradeoff is that the swirl ramp under the intake valve does reduce the airflow slightly as compared to the airflow without the ramp.

BUT, it's been shown by several people on Thirdgen.org that if you smooth out the rough casting surface & edges of the ramp, without removing the ramp, that the airflow increases substantially so you still get good swirl AND you get a lot more airflow. So porting the vortex heads (which are swirl port) is a cheaper alternative to using the 1996+ Vortec 4.3 heads.

So the head breakdown on 4.3 v6 looks like:

1988 and earlier LB4 --- conventional ports
1989-1995 LB4: swirl ramp, swirl port in the intake runner (vortex)
1996+: true "Vortec" heads, raised inlet runner, no swirl ramp

The S10 web site(s) discuss this in more detail than I have, but the info is also scattered among several threads so it's not as easy to get a clear picture.

thank you for researching this,you just answered my question.i just bought a set of 96 heads but will have the old ones ported and cleaned up and put em back on

Originally posted by jdhogg
thank you for researching this,you just answered my question.i just bought a set of 96 heads but will have the old ones ported and cleaned up and put em back on

I'm just not certain on the dates though --- so don't rely entirely on what I posted. Look at the heads for yourself and tell us if you see the differences I mentioned.