Once I decided on the 4.3, I had to decide which flavor of 4.3. I managed to find a running but tired 1990 4.3 from either an Astro van or S-10 for $100. It came with complete with intake, TBI (model 220 used on both the 4.3 V-6 and 305 V-8), two wiring harnesses and even a set of headers. Separately, I picked up a 1990 4.3 computer (GM # 1227747) on eBay. You want to be sure the computer you use does not have the vehicle anti-theft systems (VATS) that was introduced in the 1990 or 1991 models, otherwise you will have to purchase a custom chip with the VATS feature disabled.

 I used this motor as an example while I developed my swap plan.

Again, more research convinced me the S-10 truck motor was the way to go. I started checking on rebuild prices. I consulted with a friend at the local Auto Zone and finally narrowed it down to a 1990 S-10 “Xtreme” Recon rebuilt long block motor with “tin” (all the covers installed) for $1,916 plus core charge. The beauty of this motor is you only have to add the intake, distributor and water pump. It also comes “ran in” and dyno tested.

My friend called the Auto Zone rebuilder and we asked a few more questions about specific block numbers, then ordered one. I had to wait about two weeks while one was built and tested since none were in stock but I got a fresh motor. The dyno run showed 207 HP and 277 FT/LBs, a big step up from the original motor.

While I was waiting for the new motor to be delivered, I tore down the tired 4.3 motor I had bought, removing the distributor, TBI, intake, and all the sensors. I cleaned and inspected all the used parts. I also sorted out the two wiring harnesses I had and test fitted the connections.

It was at this point that I made some decisions that increased the project cost quite a bit. I decided to not use one of the wiring harnesses but instead ordered a kit from Painless. (Note: the Painless kit is designed around a 1990 GM R/V 1500 setup)  I also decided to use all new sensors and a rebuilt distributor. This decision added $805 real quick but was, I think, money well spent.

I cleaned and rebuilt the TBI, cleaned and painted the aluminum intake manifold, and coated the exhaust headers. I had motor pieces hanging everywhere in the garage while the paint dried. 

 Keep reading