Well just what the title says....

Aside from the obvious difference of fuel injection vs. carbed, and if you used a carbed engine on an injected setup you'd have to use a fuel pump blockoff plate.....


But is there anything else I'm missing?

I'm going to rebuild a 4.3 for my 1991 4x4 Blazer.... does it matter if I use a 4.3 from an early 80's carbed or injected car/truck?

With it being a 91, I don't think I've got vortec heads in it...

But would a later 4.3 with vortec heads bolt right in without problems?

 

my 91 has a vortec v6

 

Well they were made next door to my plant. Good 'ol Tonawanda, NY

 

Unless they were built at the plant in Romulus, Michigan, check your suffix code.

Just because it says Vortec doesn't mean it has Vortec heads, besides which Vortec heads were first used on truck V8's in 1996. Vortec is the label they put on engines when they changed from TBI injection.

 

As far as I know all the 4.3L V6 use Vortec heads. Over the years the design got better, and what people call the Vortec head is the newest version, which came out in '96. That version also changed the angle of the intake manifold bolts to the heads. If you run a post '96 heads, you need to change the intake to match. My '93 even has Vortec on the CPI cover.

'85 was the first year of the 4.3L V6 and it was carb'd and had a mechanical fuel pump. '86 also had a hole for the pump, however most went to fuel injection. Imade a block off plate for my '85 block. I dropped that engine into a '93 with CPI. The '93 intake and all accessories bolted up to the '85 block with one exception. I had to drill and tap one acccessory hole on the passengers head. I made a cardboard template off the '93. '85 4.3 is the only year with a two peice rear main seal. No two piece rear main seal 4.3 was ever put into an S10, you may need to make a custom oil pan, I had to for my 4x4.
Here is a link to my swap.
http://chevytruckworld.tenmagazines....sp?album=18998

Here is a link that helps explain the differences over the years of the 4.3.
http://www.babcox.com/editorial/ar/ar39840.htm

 

Read the post under "compression" swartz ran "rebuilding the 262......." I said it was a great article. It also shows the 1996 TRUE Vortec head with the good combustion chambers like the V8 Vortecs. From the picture I would think all 1996 and later are the good ones (and use different intake bolts). 1995 and earlier are run of the mill truck heads like any truck V8.