Thinking of somewhat rebuilding a 5vzfe 3.4.
Currently 300k miles. Runs fine.
but thinking of tearing it down to the block and keeping the pistons and crank in place and buying brand new heads.
Is there anything I need to do prior to installing new heads? Since the engine ran fine?


also would one recommend a rebuild kit. One that includes crank bearings, piston heads, piston rings, and thrust washers?
or should I leave the bottom end alone?

 

I'm prepping for my 3.4 swap as we speak. I'm taking the long way around though and it might be another couple of years before I get done.
I went with a full rebuild at my local machine shop having them assemble the short block, work the heads over with new valves and I've done the rest of the assembly.
you might check the dollar amounts and see if having your heads worked over rather than buying new would save you any nickels.
If you have your engine torn down to the short block you should plasti-gauge the bearings and see what everything looks like.
Without a compression test before you tear it down you can tell much, but with 300K miles on it I would plan on new rings AT LEAST if not a full rebuild, that is a lot of miles and a lot of disassembly to just ignore it and slap some heads on.

 

I can compression test it before tearing it apart since it runs.

If i just do the piston rings, do you think machine work would be necessary?

 

Depends on how worn the pistons and/or bores are. If the bores are within diameter and taper limits, then probably not.

I'd do a leakdown test before I even deciding to tear it apart though.

 

Update: I will probably be buying a 2000 4Runner, 240k miles instead.
Just, in my mind thats a 75k mile difference..lol