I’ve had a 3SGTE engine in the garage for 8 years and thought I’d spend a little bit of $ to tear it down to decide if it was worth rebuilding.   Here we go…
I bought it 8 yrs ago as a “genuine Japanese, low kilometre engine” with a handful of nice pics.

When the engine was delivered I found that the clutch was a rusted lump, the plugs were flaking a lot of rust in the plug wells and even a few cam lobes had surface rust.   I didn’t bother opening it further in case I was even more disappointed.
 

The engine looked like it might have been steam cleaned, left with excess water, and pimped up with some tyre black and new hose clamps.  And maybe then left outside for a bit.   I pushed it into the corner of the garage and threw a sheet over it so I didn’t have to look at it.
 
Eight years later and I was deciding if to get rid of the engine or not.  For $100 or so I could tear it down and decide.  I bought a stack of orange nitrile gloves (easier to see grit on them than black), a lot of sandwich bags, big felt tip pen, and a printout of relevant engine sections of the MR2 SW20 manual.

The coolant connection points had little internal corrosion which was a good initial sign.
 
The inlet air path had some oil but unclear if this is a significant amount.
 

 
The side play of the turbo compressor took a 0.6mm feeler between compressor and wall when pushed to one side and somewhere between 0.2 and 0.25mm when pushed the other way.  So total side play is 0.35-0.40mm.  Manual says 0.18mm max.  So turbo seems very worn.  The turbo model has no “CT26” labelling and may be the higher boost turbo from a Gen III 3SGTE.

Valve clearances were within spec for inlet however exhaust was over spec.  Wait until see if carbon on valve seats and any reseating of valves before thinking about any new valve shims.
 
The sequence in the manual went well until I found a headbolt where I couldn’t insert the 12-point socket.  It turned out that the splines of the cup were damaged during a previous rebuild, see https://www.mr2australia.com/mr2play/tm.aspx?m=144877.
 
The headgasket was some sort of fibre/metal construction and about 1.2mm thick.
 
Found a lot of oil residue in the camshaft area.  Cylinder head combustion chambers not too bad.

 
 
 

Three of the valve buckets had corrosion at the top.  Will need some new buckets.  The mating surfaces in the head looked OK.

 
Rubbed the surface rust off the camshaft lobes with a plastic scourer and local mechanic said that they looked fine.
Inlet valves looked good.  Exhaust valves also OK however significant carbon buildup.

Valve stem diameters were within spec and a slightly oversize 6mm drill bit shaft indicated valve guide bores were OK.  I estimated valve guide/valve stem clearance by having valve in the guide and rocking valve side-side and measuring the amount of movement of the valve head.

The valve was inserted such that it’s tappet end was at the top of the valve guide.  The valve guide is 44mm long and the valve is 100mm long.  Side-side movement  at the head  was 0.23mm.  Assuming a pivot point half way through the valve guide gives gap in valve shaft to guide bore: (0.23/2)*(44/2)/(100-44/2)=0.032mm, OK.
 
 

After removal of the pistons & conrods I measured the ring gap of a sample top ring and it was 0.65mm, outside what a rebuild would be targeting however inside the max of 0.85mm.  The piston width was 85.922mm, getting to the bottom of spec.  The bores were within spec and could still see a lot of the hone marks from the previous rebuild.  So seems that the cylinders had seen some working life.  The cylinders have not been bored oversize.
 
One of the bolts on the big end of #3 cylinder was easier to undo than the others however the crankshaft of #3 cylinder was fine.
 
When removing the crankshaft I noticed that some bolts were dry and some  had significant oil on them.  There may be a slight gap between the bearing cap surfaces around some bolts.  However the crankshaft was fine so it can’t be that significant.

The crankshaft sizes were not undersized indicating the crankshaft hadn’t been reground undersize.
In summary the engine doesn’t seem to be too bad.  The big item that was out of spec was the turbo and this may have been the source of the significant oil residue in the engine.  The turbo and clutch indicate that the engine had been rebuilt for some low level of performance, unclear what boost, however it can’t have been too high as the rest of the engine is pretty standard.
 
Very little need for special tools.  A 12-point socket for the headbolts and some lengths of 6mm steel bar that I drilled for removal of crankshaft pulley and flywheel.

 
Looks OK to invest some rebuild $, now to order some parts!

I wasn’t going for horsepower so followed the following advice: http://www.mr2.com/forums...php/t-82566.html  “As long as you don't plan on going too crazy with power mods (under 300hp), most aftermarket kits seem to be "good enough". I would run a genuine head gasket or a quality metal head gasket with ARP studs. Don't skimp on quality bearings and make sure the piston rings are good as well with proper gaps. Don't trust that any clearance is correct out of the box. Just build it right or it can/will bite you in the end.”
 
Then onto Google to find the most popular generic rebuild kits.   This seemed to be MIZUMO, Domestic Gasket or Performance Part.  They had each sold more than 30 3SGTE rebuild kits, had good Ebay rating, and seemed to be based on the same brand components, King bearings, NPR rings, GMB timing belt components, and AISIN pumps.  Some only had oversize pistons or undersize bearings and I ended up with Domestic Gasket.
 
Oil seals, head gasket and timing belt were included in the kit however I bought a COMETIC head gasket and went to twosrus to get some OEM bits: timing belt; hoses from hell; turbo gasket kit; front and rear main seals; camshaft seals; and a distributor seal repair kit plus a set of silicone coolant hoses.
 
The rebuild kit comes with valve seals however I was wary about quality.  Valve seals were hard to find elsewhere and I bought SuperTech viton seals with spring collars.  Mixed reports on the web about them being OK or not.  I was concerned with possibly having to remove the head to replace them later however then found a description of how to replace valve seals with head in place using compressed air down the plug hole to keep valves seated, very neat.  So could replace them later if an issue.
 
ARP rod bolts. 
 
I didn’t get ARP studs even though they are very popular.  When I looked at the ARP instructions they say that they should be retorqued after 500km or so and the OEM bolt design doesn't need this.  I’d bought some NHP bolts that were similar to OEM however they turned out to be a poorer design than the OEM bolts, with a step in the shaft rather than a chamfer (stress concentrator?), a slightly shallower socket hole, and slightly looser fit of the 12-point socket than the OEM bolt.  Generally a rougher implementation which makes you wonder about the quality of the steel and production.  So ordered OEM bolts from Nengun – don’t ask about the shipping cost!
 
New thermostat.
 
The exhaust manifold of this engine was a 9-stud even thought it was gen II.  Some talk that later gen II came like this.  The ECU serial number of this engine indicated that it was from 1993, the end of the gen II series.  Turns out that you can’t get an MLS 9-stud gasket anymore and the 7-stud gasket is intended to be used on either 7 or 9 stud pattern.
 
Hunted around for some valve buckets to replace the three corroded ones.  Seems that the same bucket was used on a number of Toyota engines and I found some unused 32mm V6 ones for sale.  Wait and see fit.
 
Won’t know what I might need in the way of shims until I reseat the valves and reassemble the engine.
 
Now waiting on parts to arrive.

Wondered about fuel injectors - the engine in the car has done 200,000km (JDM import ODO?) and the engine I'm reworking an unknown amount but seems a bit younger.  Both are side feed injectors.  I decided on using the fuel feed and injectors off the working engine, one less thing to debug when installing the new engine.  Injector life is said to be around 1bn cycles which would translate to around 500,000km so should be OK.  Keep the other injectors as spares.

Your injector are 440cc as is a Gen 2. They will max out at 180 to 200 rwk that's 14 to 14psi. ct26 is a gen 2 turbo not Gen 3 that's a 20b.

Injectors should be ultrasonic cleaned and flow tested regularly (every few years or depending on use). Working or not you can't tell the spray pattern and flow. The cleaning and testing ($150 from places like injectors online) will tell you more about the injectors. Personally I would spend the extra to get some 3sgte gen 3 / supra 540/550cc injectors, drop in / connect on, allowing 16-18psi (depending on fuel / spark gap etc).
Limit is then not the injectors but the rail and the ecu (timing pull when running bad fuel).

Best to run a wideband for afr awareness. Justraceparts (from memory) has a quality wideband and gauge for $230 - owner is a MR2 owner :) support the circle.

Look on the turbo exhaust housing for 740xx as in 74020 (ct26) or what it is.

You want two websites in your life, megazip.net is an easy to use menu system of parts diagrams and parts numbers, Amayama trusted to deliver as per part listing (can be half the price of nuegun and a quarter the price of twosrus when Inc postage) for OEM parts. However always shop around :)

If you need buckets let me know I have lots spare you can have.

Thanks for the feedback Guys, the turbo I removed, on the left in the next pic, had no CT26 marking which some sites suggested was a CT20B.  However it does have the 74020 marking so I guess CT26.

 
 
I had already ordered a wideband sensor and gauge with 1.1V output so that I could use it with existing ECU and also be able to more closely monitor the air/fuel ratio.
 
I did look at new injectors and the 540/550cc looked like a common option however Heicks MR2 Handbook said that this would give very poor operation with the standard ECU.  Were you assuming that I was going with an aftermarket ECU?  I do have a Megasquirt ECU that I'd used briefly in the past however I was wary about trying to get too many parts operating at the same time.  Maybe I should go further down the rabbit hole with the bigger injectors and the Megasquirt ECU.  When I used this ECU in the past I did like the idea of being able to do away with the airflow meter.

Terry Hiecks, nice editorial for the mr2 written in the mid 2000s (part truth, part heard of info from others, part story writing).  Removed a lot of words cause being nice.  In 2021, best to listening to those who have been working on, repairing, modifying and analysing the mr2 before Heicks and still today.  KO Racing, ATS Racing, Wilhelm (aero and suspension) and many others.  Religions, politics, MR2 (3sgte or not), and 3sgte ~ everyone has a different path and opinions.
 
Megasquirt IMO sell it to someone you dislike or owns a different car.  Stock ecu or modern aftermarket.  You dont have a 5s block, havent half filled your 3s, not forged internals (blocks the weak part at around 450 rwhp or so, where the stock gen 2 rods can hold up), so your not going for huge hp, bang for buck is stock ecu.  Stock ecu, cleaned and flow checked gen 2 or gen 3 injectors and various other mods and details (like spark temp and gap) items that are bolt on and work great, proven through the past 15 years.  Monitor your afr, dont rely on an ecu.

Best to do the valve seals now, gsc are quality and cheap (sub $50). To do later is using a $170 Leslie tool.

Many choices that are yours for your build your outcomes.  Enjoy the journey.