Hey all, question about converting a 4.0 block to 4.6 crank. My truck is a 2000 4.0 and I have a donor 2003 4.6 with good guts and a questionable block. Are the benefits of using the 4.6 crank (and an upgraded cam) lost, if I use my '00 ECU?
Not sure if remapping a 4.0 ECU is possible, necessary, or economically feasible.

I can't live with trouble codes from using an '03 ECU that wants to see secondary air. Pennsylvania emissions requirements will not pass any TC's where I live.
I'll just rebuild the 4.0 if it's not worth the upgrade effort. Pretty sure I can at least drop in a cam upgrade..
Thanks, -Bill

 

The benefits won’t be lost completely. Over time sourcing an ECU from a later truck with 4.6 will definitely wake it up. I used a crower cam for my rebuild. Pretty happy with it. Tornado systems can tune your current ECU for the 4.6 as well as their tune. Make sure you use the larger MAF and intake hose and filter box top from the 4.6. Good info on tornado systems website

 

Thx for the reply. I have a complete 03 donor truck, but if I use the 03 ecu in my 2000 truck, won't it throw codes for secondary air that it won't have? I wonder if it's possible to toggle the SAI off with a Hawkeye or similar? I checked Tornado's site and I really don't have the budget for a custom tune at this point. Maybe in the future, but I just want to have a running engine without a CEL, using my existing resources for now.. -Bill

 

You can flash the ECU with a non-SAI tune, but I think it requires the factory LR computer. My independent shop was able to do it.