I'm looking into buying a 1990 Sierra that's for sale in the area. It's got a V6 in it right now. Would it be a direct swap to put in a 350? Would I just need new mounts and new springs, or would it not bolt up to the transmission?

 

I'm sure the tranny is completely different. It really isn't worth it to do that. Your best bet will be to find a truck that already has a V8 in it. Unless of course the whole purpose of this is for this to be some project truck. It's gonna be a lot of work though! Your talking about swapping the whole fuel deliverys system, tranny, driveshaft, front end suspension and you might even need bigger brakes on the front. I wouldn't do it.

 

OK..... its not that serious of a swap... just went right through all of this a couple monthes ago. tranny will bolt right up no problems, you may need a new flywheel/torque converter not sure on that i replaced mine anyways while i was down there. as for the fuel delivery youll need larger throtte body and youll have to change knock sensors, the electronic spark control and some other ecm sensors but as far as the suspension goes it should be all the same on that body style. got to remember here the 4.3, 5.0 and 5.7 are all the same block just bored differently and with different heads and different intake with the 6cyl obviously.

 

Is his wiring harness gonna plug right into the V8's ECU? What about fuel lines and the fuel pump?

 

yes the wiring harness will be exactly the same. fuel sending should be exaclty the same however i did forget in the post to mention hell need a new ecu for v8s as the v6 ecu will not work at all.

 

I'm used to talking about old sports cars. I know on a lot of old cars you have to replace a lot more stuff to do engine swaps. Like when I had my 72 Charger, I was gonna have to replace the whole drivetrain, all the mounts, the front cross member, the front end suspension, and all the fuel lines, just to put a big block in it. Talk about money........ glad I sold that thing!

 

Alright Spaz, you're close but no cigar, LOL! The 5.0 and 5.7 are the same block, different bore... the 4.3 is a 6 cyl. The 4.3 and the 5.7should bethe same bore and stroke, but the 4.3 is missing 25% of the block, it's like a 5.7 with the rear two cylinders cut off....

Suspension-wise, the truck should be able to handle the swap. I'm not sure, but the tranny should bolt up(as stated above, the flywheel and T/C may not be compatible due to balancing issues). I have NO CLUE about the wiring...but would assume they are correct about the v6/v8 ecu not working!

 

I'm sure we all realized that already.

 

yes forgot to edit that post. but the wiring will be all the same still.

 

Thanks for the reassurance..... I was just pickin' on Spaz about the blocks....didn't mean to offend you!