Mason Saban

I have major questions as I have a 1994 c1500. Had the 4.3l v6. I'm going to put a 305 into the truck with the original trans. My question is, what do I need to do in order to make 305 work properly with the existing trans? I believe the trans itself is a 4l60e. Just not sure how to go about this. So any and ALL help would be greatly appreciated.

oilcanhenry

Beyond what you ask here, I would HIGHLY recommend using the 350/5.7 motor. The 305 is simply a lesser motor, and will not have the horsepower that a 350/5.7 does.
You will likely find that not only is the 305 of lesser horsepower, but your fuel mileage will not be _any_ better then that of the more powerful 350/5.7 engine as well. the 1994 4.3L as rated at 165 HP at 4000 RPM. The old 305/5.0 at 185 HP, but the 350/5.7 was rated at about 210 horsepower, all with older TBI fuel injection systems.

In either case I dont think that you will have many issues to contend with, but you will have to obtain a fan shroud that is smaller then the 4.3 liter fan shroud. You may also have to convert the air-conditioning system to use R-134A, but you are right at the piont where you may well already have an R-134A refrigerant system. and not R-12. In either case a 1994 vehicle will not have an OBD II engine code system, which can be a real bear for a DIYer, but there are lots of techs who have OBD I scantools, so its not really a major issue.

cardsfan119

I just put a 5.7 in my 1995 K1500, swapping out the original 4.3. Pretty easy for the most part. I bought a used engine locally off FB marketplace with comparable miles to my truck (127,000) that came out of a 2WD 1994. The engine was complete air cleaner to oil pan. I then made list of parts I didn't have or needed replaced and bought them from Rock Auto for less than $300.00. I needed a different radiator, upper and lower radiator fan shrouds, and radiator hoses. (I'll just warn you the two bolts on the lower radiator shroud were a bear to remove and install.) I also replaced the plugs and wires and rebuilt the distributor as they appeared to need it. I needed different engine mounts for the 5.7 (I had zero trouble removing the V6 brackets or installing the new - I used either a box end wrench or breaker bar with a socket and an impact wrench and got to all the bolts easily). I happened to have the correct PROM chip for the 5.7 so I switched that (If you don't have one check Ebay they are available there and one of the bigger sellers, if you give them your configuration, will match the right chip for you). The V6 had two knock sensors, and the 5.7 uses only one. I just abandoned the drivers side one and had to lengthen the passenger side one to reach the location behind the starter on the 5.7. All my other harness connectors matched right up. I anticipated having to change my fuel lines, but surprisingly they reached as well, though I did have to bend them some. Exhaust and transmission all plumbed right up with no issues. I also replaced or shortened the heater hoses. I then just went through the normal post install trouble shooting, checking for leaks, and making adjustments. The SES light came on, and when I pulled the code, it showed no knock sensor signal. It turned out the sensor itself was bad, and after replacing it the light went out and hasn't come back. It drives like a different truck, no comparison between the 4.3 and 5.7 in terms of HP and acceleration. I agree with oilcanhenry though, if your going to do it, skip the 5.0, and either put in the 5.7 or just replace the 4.3. The aggravation is not worth 20 extra HP, especially with the added weight. There is probably some performance upgrades for the 4.3 that could get you the extra HP for a fraction of the cost and time. Good luck!