All was well for a little while...then I started to do some digging into my motor. Pretty much every time it got over 200 degrees weird gunk would collect at the radiator cap. I decided to finally pull the data off the stock PCM and see if there was a different MAP table that I could use to fix the nagging MAP error that was bothering me and constantly turning on the CEL.
It confirmed my fears, I had (past tense) a 4.8L motor instead of the 5.3L I thought I bought, thanks Craigslist. So this happened.
Then this happened.
The new motor is a 2009 LY6 from a 2500 pickup. Its a Gen IV, iron block, VVT engine. I chose to keep the VVT intact as its not a dragster and Chevrolet tuned this motor for torque, 380 ft-lbs. I also took the time to go to Corvette style factory manifolds to cut down on noise and heat. The problem with these is they are wider than my Sanderson headers, so I had to move the steering column over.
I used a double joint to point it back at the 80 steering gearbox and then a giant rod end to support it and keep it in place.
I also decided to modify the stock LY6 wiring harness and move the PCM location to the engine bay and free up some space under the very cramped FJ40 dash. I laid out the harness on the garage floor and pulled out all the circuits I didn't need but it gave me the opportunity to keep some like the EVAP purge that aftermarket harnesses never do. Collect up all the pink wires and figure out where they go with a multimeter then I turned that into a connector for harness power.
I made a separate connector for the data part of the harness to ease trouble shooting in the future.
While I had the harness apart I added a wire to the main PCM connectors for tach output and I changed the wires around for the APP so I can use a Corvette style pedal. The truck pedals are HUGE and use a different arrangement than the corvette. I also re-did the MAF wiring so I could use an LS3 style card MAF. The stock LY6 MAF is in a 3.5" tube and my intake is mostly 4" tube. The card MAF lets me use a 4" tube section from Spectre with the MAF mount already welded on.
I also changed the water pump to an LS3 style which moved the outlet over to the driver side and pointed forward. To do this I had to use a combination of the stock truck alternator and power steering pump mount and then the LS3 tensioner but the arrangement looks cleaner to me and I kept the LY6 pump with double returns.
Since I had double returns I figured I'd try Hydroboost. The hydroboost booster opened up a ton of options for master cylinders to go up in diameter and push more fluid for the huge front calipers. I ended up using a Dodge master cylinder for its low profile and had to re-do some brake lines with adapters.
Here's how it came together.
It's back up and running now and I'm refining the tune for the new motor. It definitely has a different personality than the 4.8 tune and drives like a 2500 pickup....steady torque and you have to mash it to fly. It's not as fun, but a better match for a 5800lb FJ40/45. Since the computer controls how the engine responds to the APP position I can tweak it some down the road. For now just drive it and see how the engine and the hydroboost conversion works.