Ok, a year ago I pulled a TBI 4.3L V6 out of may 1994 chevy Astro van (2-wheel drive) which said "Vortec" on the composite valve covers. This led me to believe that it had vortec cylinder heads as apposed to the previous swirl port heads (kinda like the gen. 1 V8's). Now comes the confusing part. This last weekend I pulled a 4.3L V6 out of my 1991 c1500 pickup. Now I have been told by several mechanics that this truck did not have the vortec option and it was the old-style TBI GM 262. However, it and the '94 astro motor are identical. I even went as far as to pull the intake and valve covers and swap them, they bolted right up to both blocks.

Now most of my experience and knowledge lie in the v8 blocks so what I need to know is are they BOTH vortecs or not. I always thought that centerbolt valve covers were a dead giveaway to a vortec head.  However it looks like all the s-series trucks had centerbolt covers on all the 4.3's, vortec or not. PLEASE HELP. Vin code on truck is "z", and I don not remember the van's code.

I knew the previous owners of both vehicles, and both bought the vehicles new, so I know these are the origional blocks.  

Well, "Vortec" has been used rather loosely around GM for a while. It's been used to refer to the 4.3L V6 for quite a while, and then was applied to everything from the 1996 CPI 5.0 and 5.7 V8s in the trucks, and later to the 2.8L and 2.9L DOHC "modular" four, 3.5 and 3.7L five in the Colorado, and 4.2L six-cylinder in the Trailblazer. It is also applied to all of the new Gen-IV V8s in the trucks, from the 4.8L all the way up to the 6.2L V8. So the term "Vortec" in and of itself it essentially meaningless in terms of identifying a specific engine or engine family.

As far as the Astro specifically, I think there were a few model years where the TBI and PFI engines were both offered. So it's entirely feasible that the engine in your '94 Astro and your '91 truck are the same. Also, the 4.3 V6 has been the lone holdout that has changed relatively little while the V8s have undergone some pretty major changes, (starting with the 1999 model year pickups.) I don't know if this answers your questions at all or not. Hope it helped some.  

Well, I did help out quite a bit. I mainly need to know because one of these will be reborn into a fire breathing beast compliment of some major boring work and a stroker kit. And for a few parts, like intake manifolds, some cams, and con-rods, there is a different part number for Vortec and Non-vortec, Specifically the intake. Now on the v8's (gen. 1 mind you) the intake differs by a different angle between the intake and heads themselves, however both the v6's intakes are interchangeble.

After posting last night I actually removed the right head off each block to compare, now the puzzle becomes more interesting. Their different! The van motor's head had the distinctive heart shape port in the combustion cahmber, and the truck's had the standard swirl-port chamber. So if the van motor is clearly a "vortec", why would there be a different part number for the intakes. I can attest first hand that a "vortec" intake will fit on a standard block. What is summit refering to as a 1991 vortec if the intake is the same? edelbrock part numbers are EDL-2111 and EDL-2114 for the standard and vortec engines respectively.  

Just because something will bolt up to something else, doesn't necessarily mean it's the best choice. I would stick to the parts designed to work with each other, i.e. Vortec-to-Vortec, etc. I'm sure there are probably some components that will bolt up between the TPI and PFI 4.3 V6s, but they're clearly different engines.  

I think may have confused some of ya out there, my apologies. The plan is to take one of the blocks (prefferably the '91 truck because it doesn't have a balance shaft) and turn it into a big bore/stroker. The only reason I'm having the vortec dilema is because as esanchez mentioned, components may bolt up to a block they were not designed to fit it. This is where I mentioned that the intakes have different part numbers for very similar parts. This is why I need to be certain which blocks I currently have so I can get the right parts. Sorry for the confusion. I also plan on using the "vortec" heads on the 91 block because I've heard they not only flow a little bit better stock, but they also have thicker metal on the runners for extra porting work. The stroker kit will come from Speed-o-Motive with all forged components and around a 10.0:1 compression. Do I use the intake designed to fit the heads or the one designed to fit the block?  

Usually, it seems like the intake manifold bolts to the heads, not directly to the block. So, given a choice, I'd probably try to match up the manifold and the heads. I think that's probably where you're going to see the most difference.  

sweet, that's exactly what I needed to know. Is it safe to say then that the block is a non-vortec and all it's internals can be replaced with the non-vortec variety?  

You can never necessarily assume anything. But in my experience, GM changes things up less often than say Ford or some other carmakers. Especially when it comes to the 4.3 V-6, I'd imagine a lot of parts interchange over the years. Let us know how it goes.  

Hey, I found a few tech articles on the Hot Rod site about building up the GM 4.3. Hope these help:

<u>&lt;strong&gt;The 3/4 350&lt;/strong&gt;</u>

<u>&lt;strong&gt;500hp From 270ci&lt;/strong&gt;</u>  

whats the vin? i can look it up on my gm stuff at work  

The vin is "1GCDC14Z3MZ113160"  on the truck, and I don't remember the van's code. thanks for the links on the 4.3 build ups, the blower kicks some serious a**! A quick search led me to a site that makes stroker kits for these blocks. The company name is Speed-O-Motive and I've heard lots of good things about their 350 kits. So I think the new plan is to use their 4.5L stroker kit with a .60 over bore to yeild around 4.9L, with all forged internals. A little more searching found some pricey, yet worth it heads from brodix that should give the 4.9L some muscle. Said and done, I think I should have a motor capable of around 550 horse with a 150 shot, and that in an s-dime would be beyond words. Not to mention I would have enough parts left over to build another motor. So I thank you for the knowledge, and look for a thread on this "sleeper" build in the future.  

Should be interesting. A lot of guys just swap a 350 in S10s, which is fine, but I think getting a lot of power out of the 4.3 is more interesting, and more of a challenge. We look forward to your future installments!