3.4 swap to an 85 4x4 jimmy

[son_of_a_jimmy]

Im kinda new to this 60 degree stuff but from what ive been reading, if its done right this motor can be a pretty sweet little SOB. I own 2 jimmys one is a 2wd that was my first truck and i fixed it up and am putting a 383 in it but i recently picked up an 85 4wd jimmy for an everyday driver. I have a 5 speed lined up for it and i thought a 3.4 would be a nice upgrade too. So i just wanted to see if anyone else has swapped a 3.4 into 4x4. if so it would be nice to here how it went. thanks.



Weston

[geoffinbc]

I have done it in my 2WD and it is a hell of a fun motor. Not V8 power but it can still lay a good patch and return respectable mileage. If you are going to use yours as a daily driver and mild 4X4 stuff you'll love it because it packs more punch than the 2.8L but weighs the same so it wont make an already heavy vehicle, heavier.

[son_of_a_jimmy]

Sweet sweet, sounds like im headed in the right direction. thanks a bunch!

[son_of_a_jimmy]

Also, i was wondering what heads would bolt up. i hear everyone talking abuot 3400 heads and 3500 heads. i have a carb on my 26 now and i plan on keeping it carb b/c swapin the wiring for a tbi is just to big of a pain. so i was wondering what heads bolt up and any other parts that can be swaped in and out from a 2.8 to a 3.4 for my truck.

Thanks

Weston

[bszopi]

None of the aluminum heads will bolt up to a carb manifold.

[geoffinbc]

Agreed. Your going to have to stick to Iron heads. But be sure to gasket match and blend the ports on both the heads and intake. Also remove all casting flash on both the heads and intake. The stock manifold is suitable for street use and if you wish you can upgrade to a Weber or Holley carb for some more performance.

[son_of_a_jimmy]

so if i get my iron heads ported and polished as best as possible, they will put out about the same horse as the aluminum ones? or would it be worth it to get oversized valves and such?

[son_of_a_jimmy]

i was also wondering what was the reason a carb intake won;t bolt up to the 3400 heads, is it the bolt pattern or is it just completely different?

[son_of_a_jimmy]

another thing if i was going to buy a performance cam, would i buy one for a 2.8? and if so any recommendations?

[geoffinbc]

You can port the heads but they still wont flow as much as 3400 heads. However iron heads are good for low end grunt. The iron head intake isn't even a close match for the aluminum heads. The port layout and bolt pattern are different. When buying a camshaft just buy for a 2.8L or 60degreeV6. Flat tappet hydraulic cams are available from GM, Crane and Comp there are a few others but for fast delivery and availability go with the 3 listed. For off road/street use I would not go with anything bigger than a 260 (referring to advertised duration) cam. You may even consider something more mild like a 250 to 255 to help low to mid range torque. Get the one with the largest lift and maybe even add some 1.6 ratio rockers to help that low end airflow. You will have to upgrade valve springs as well.

[son_of_a_jimmy]

Thanks for the info~!