91 old school swap

[papsoldblue72]

I have a 91 1500 Silverado with a 4.3, and 5 speed manual. I'm wanting to swap in a 350 and keep the 5 speed trans. Is it possible to use the existing flywheel, water pump, pullies, and engine mounts? Please help....

[Palf70Step]

V6 engine mounts are different and pretty sure the 350 will not fit sitting that far back. Far as the rest of the stuff it should all work. Make sure you use all the accessories as the serpentine belt rotates reversed of the normal V-belt setup. I know the trans will work, I am not positive if the flywheel and clutch are the same or not. Pretty sure it will work, but the clutch is smaller diameter for the V6 vice the V8.

[1976gmc20]

Man if you're going to go to that much work, try to find yourself an NV4500 and throw away that lightweight 5 speed which is what I'm pretty sure that you have.

[papsoldblue72]

Originally Posted by Palf70Step

Far as the rest of the stuff it should all work. Make sure you use all the accessories as the serpentine belt rotates reversed of the normal V-belt setup.

Okay the main thing I'm wondering is the water pump going to bolt to my old school 350.. I've heard the mounts are different, but where can I get the right ones??

[papsoldblue72]

Originally Posted by 1976gmc20

Man if you're going to go to that much work, try to find yourself an NV4500 and throw away that lightweight 5 speed which is what I'm pretty sure that you have.

Sorry dude just using what I have.... Plus I'm not going to beat on it too much right now...

[Tx Firefighter]

I've done this swap a few times.

V8 mounts will bolt to your existing crossmember once you remove the V6 frame mounts. Then the engine will bolt to the trans and no driveline mods will be needed. The existing flywheel, clutch, bellhousing bolts and starter will bolt onto the 350 as long as it's a one piece rear main seal engine (newer than 87). If your V8 is a 2 piece rear main seal engine you will need to change the flywheel to match.

To do it right you'll need the proper V8 fan shroud.

The lower (crankshaft) pulley will need to be swapped for the proper V8 one as the V6 harmonic balancer is thinner than the V8 one so the V6 pulley is deeper dished to compensate for the skinnier balancer. Everything else on the front of the engine is a straight bolt on to the V8.

You can reuse the existing V6 ECM and wiring harness as long as you install the proper 350 PROM chip into the computer. All of the plugs on the V8 will be the same as the V6. You will need to slightly pull the wiring harness further forward into the engine compartment to reach all proper locations on the V8 but you won't need to mod it.

[papsoldblue72]

Originally Posted by Tx Firefighter

I've done this swap a few times..

Thanks for the info... Guess I'll need to find some stuff... lol

[LT7A]

Wow, good info TXFF. And paps, if you've got an NV3500, I don't think you need to worry, as long as you're not hammering on it. I looked into those as a lower cost alternative for a 5-speed, and they will handle a reasonable amount of torque.