The rebuilt engine should be going back into the car tomorrow or Friday.
I figured out why the engine was overheating. The previous owner had changed the coolant hoses around when removing the heater and created a permanent coolant bypass around the engine! I hadn't realised until the engine was on the engine stand and I could see everything properly.
The coolant line that would normally go through the standard oil cooler and then into the back on the block was blocked off, which also contributed to the cooling problem. I have now put a line in past where the oil cooler used to be and then back into the block next to #4.
I'm not happy though at least I know what the cooling issue was now. It should be reliable from now on.
I had the engine rebored and CP forged pistons added. Rods shot peened and ARP rod bolts.
Fully balanced and all other parts bought from Lithia Toyota. It's best to go genuine Toyota when it's affordable.
New oil pump, water pump, valve springs, harmonic balancer and bolt, new timing gear, TRD thermostat and lots more.
I even bought a genuine dipstick tube and O ring!
I can't wait to have it running (and reliable) 











 

Can't help but feel happy for you :)
A bit dodgy with the coolant mod from previous owner but atleast the car is perfect now

Looking good.
Im scratching my head about cooling options with the engine, finding some information on it but a little unsure about the flow through the block. The Toyota manual shows the coolant goes from the water pump into the block and head, then to the opposite side of the engine where it is then distributed to the heater,turbo and back to the radiator. The lines to the heater and turbo then return to the water pump via the bypass lines located behind the turbo. They also feed through the oil thermostat/cooler before entering back into the pump to be cycled through the system again. While running a dedicated oil cooler and being a race spec engine, there is no need to run the oil thermo/cooler,throttle heater(imho)or any of the return lines. To me it just looks like you throwing superheated coolant(via turbo) back into the system without sufficient cooling.
Am I missing a coolant line which is used to circulate through the block? Can you clear this up for me?
Have you considered running the turbo outlet into the radiator return line or a mini radiator which can tap back into the return line at the rear of the water pump? After having a closer look at the system today(thanks to your issue) It could help with reducing recycling hot coolant and lower operating temps. I figured the other advantage of removing all the lines(aside from weight..) is less work for the water pump, improved flow rate.
 
Cheers
 

I haven't tested it though I think the water will flow the other way through the coolant pipes to what you described. EDIT - this is incorrect. The flow in all three pipes flows INTO the thermostat housing
There are three pipes;

• One goes from the water pump and ends at the coolant outlet near the distributor and is switched by the end of the thermostat. i.e. when the engine is warm, this pipe is blocked. That's all it does.
• Another one goes from #4 cylinder, through the oil cooler then into the thermostat housing. This is not switched in any way.
• The third one goes from the coolant outlet, then the heater and back to the thermostat housing. This line also feeds the turbo though it's in parallel to the main pipe - the turbo gets its input from the coolant outlet on the head and it's output goes into the larger pipe that feeds back into the thermostat housing.

For the first one listed above, I blocked it.
For the second one, I bypassed where the stock oil cooler used to be and it feeds from the block to the thermostat housing as per
standard configuration. (I have a stock GT4 so checked that I had it correct)
For the third one, I blocked off the end where it would have gone to the heater and also put a plug on the end where the heater also would have connected to the coolant outlet. The pipe still feeds the turbo though.
I remember that Unique Autosports had a SW20 in there a while ago that had cooling issues. They had changed just about everything and I don't think they had it fixed before they sold it. I reckon the heater pipe was looped back to the coolant outlet just like mine was. The symptoms were the same - it would only overheat when running under a lot of power.
Here are some pics of the pipe that goes back into the block next to #4.

Here are some more pics.
I'm preparing the engine bay at the moment. I'm moving the fuse box to the boot and also fixing the engine loom so I have just one big connector so I can disconnect it easily from the rest of the car.
The wiring is a nightmare at the moment.
 






 

Forgot to answer this question - "Have you considered running the turbo outlet into the radiator return line".
It already does this in the standard config. The return from the turbo goes straight to the coolant outlet on the head (which flows to the radiator) and the inlet coolant pipe for the turbo is from one of the pipes that comes from the water pump.

Looking good.
 
What connectors are you looking at for the engine loom? Im also doing the same, with Deutsch autosports, or you can use the HD series, little bigger but much cheaper.
 
Also notice you have thread sealant on some of the AN hose ends, i wouldn't do that, as the hose end seals on the flare, not the thread, so all the sealant isnt doign anything, but could attract dust/dirt ect.

I have been told that Subarus have engine loom connectors like the ones I want. I have yet to go to a wrecker to get some though.
I'll post pics when I find something suitable.
Thanks for the tip about the sealant.

Thanks for posting the pictures on the build. Its looking good and can appreciate the effort involved. It really is never ending.
Thanks for the info on the outlet at number 4. That really does help but I think that is an outlet that recycles back to the pump with the turbo added to it. It may be there to keep the engine warm in the cooler climates of Japan as it does not cool through the radiator but straight back to the pump. This could be the reason for overheating issues with the MR2 as it does not have a chance to cool correctly under load. It heats up then its straight back into the engine right behind the turbo. With this constant cycle it be causing the engine to overheat. For high temp climates it may not need this.
Here is a link to a diagram where I have based my theories on the cooling system and the path it follows.
http://www.toymods.org.au/forums/tech-conversions/46709-3sgte-cooling-system-has-me-wondering.html
The outlet at number 4 could go directly to the radiator with the turbo instead of the by pass system. Maybe it has a added advantage of providing a consistant pressure by cycling back around the system quickly? Just a guess.
Anyhow, it looks like we will be having some fun on the track next year! When Ric Shaw come out to tune the handing, your welcome to come along so he can have a look at your car too.
Cheers
 

I'm not so sure that diagram is correct. For example, the pipe from the oil cooler is shown incorrectly. It does not feed back into one of the two pipes - it actually connects to #4 cylinder via a third separate pipe. This is the same on both my MR2 and my GT4. Both are import engines.