Gen 4 to Gen 3, what you need to know

This is not meant to be all inclusive, but since I am building an engine for my Gen 3 from a Gen 4, this is what you need to know.

It may be possible to directly put a Gen 4 engine into a Gen 3, but you will need at a minimum the following.

1. Exhaust manifold and piping from Gen 4 donor car back to muffler. Might be able to get by with 6-8 inches of piping behind secondary catalytic converter. Also need EGR cooler. The Gen 3 cooler and tubing will not fit the Gen 4.

2. Complete lower radiator hose from Gen 4 donor. The Gen 4 water outlet bolts to the back of the head. Gen 3 is pressed into the head.

3. Both heater hoses from Gen 4 donor car. The hoses from attachment to heater fittings sticking out from the firewall.

4. Complete intake manifold and airbox from Gen 4 donor car. This includes all the crankcase vent hoses and miscellaneous small vent hoses attached to airbox and valve cover.

These are the differences that I ran into trying to put my low mileage Gen 4 engine into my Gen 3. Not an all inclusive list, Your experience may vary.

 

5. Flywheel and Transaxle Damper. The damper splines on Gen 4 are larger then Gen 3. The Gen 3 damper does not fit Gen 4 flywheel. The Gen 3 flywheel DOES fit the Gen 4 crank though.

 

I was hoping to have an 8000 mile engine versus a 90k mile engine for the same amount of money. I should have just walked away a week ago when the yard was pulling parts after they had my cash.

 

If I had to do it over again, I’d buy a short block for the Gen 3 engine and rebuild my head. That’s basically the point I’m at now.

 

Rebuilt head can be sourced from most parts stores for around 500 exchange. Have not found a source for a short block other then Toyota. About 3800 if I remember correctly.

 

Sensors and such on the Gen 3 and Gen 4 block are identical. If you have the complete lower radiator hose assembly from the Gen 4, it would hook up between the engine and radiator with no issue I believe. You would have to tie in the coolant hoses to and from the throttle body to something.

My car runs and drives as if it has a Gen 3 engine under the hood, because all of the electronics hook up exactly the same on both engines.

One strange thing I found, the metal fuel rail pipe is the same on both generation engines, but the quick connect is smaller on the Gen 4 where it hooks to the feed from the tank. Reduction in available fuel volume to injection to reduce ICE horsepower?

I still have the head from the Gen 4. It is missing a couple valves, and needs cams. Someone local to the SW Indiana can have it. It’s taking up space, but far too valuable to just throw it away.

 

In my area, the Gen 4 engines are running 50-75% of the asking price for Gen 3. And the Gen 4 have less then 20k miles.

 

In the spring/summer without A/C it will do 55-56 mpg. Or 600 mile per tank. Really close to the threshold of doing 700 miles per tank. Here in the fall winter with the warm up penalty, it’s running 400 to 500 miles per tank. It does not really seem to run much differently then it did when I first got it. It did have a slight “noise” in the engine when I first bought it. Maybe a collapsed lifter.

 

Kind of hard to see the level in the lighting available, but this is 3000 miles since the last oil change. To me it doesn’t look that much different from the day I poured it in the car. I hadn’t used enough to be able to tell it on the stick.