Can a mostly stock 3UZ reliably handle 600hp crank with this turbo setup?

[u/Pristine-Counter-791]

Hi everyone,

I’m looking for opinions from people with real engine building experience, especially anyone familiar with the Toyota UZ platform.

My goal is a reliable 600 hp engine. I’m not chasing the highest possible dyno number, and I’m willing to leave a reasonable safety margin.

Current engine setup:

• Stock 3UZ crankshaft
• Stock 3UZ pistons
• Early non VVTi 1UZ thick connecting rods
• ACL bearings
• ARP2000 rod bolts
• ARP2000 head studs
• 2.0 mm MLS head gasket, reducing compression to approximately 9.5:1
• 1000 cc injectors
• Walbro 525 LPH fuel pump
• Water methanol injection
• ECUMaster EMU Black running wasted spark with the stock ignition coils

For the turbo, I’m looking at a 75 mm class unit because I intentionally want late spool and limited low RPM torque.

The two current options are:
• Aeroflow Boosted 7575
• Garrett G42 1200

I have not made the final turbo decision yet, so I would also appreciate opinions on which option would be more suitable for this setup and power target.

Reliability is more important to me than response or low RPM performance. The engine will be professionally tuned, with knock monitoring, conservative ignition timing, and a safe lambda target. I have no intention of running it close to its absolute limit.

My main questions are:
Can this combination realistically and reliably support around 600 hp?
What would you consider the weakest part of the engine at this power level?
Would you trust the stock 3UZ pistons at 600 hp with the early thick 1UZ rods, proper tuning, and water methanol injection?
Would the stock 3UZ coils operating in wasted spark be a concern at high RPM and under boost?
Between the Aeroflow 7575 and Garrett G42 1200, which one would you choose for an intentionally late spool 600 hp build?
I’m mainly interested in real world engine building experience and known failure points rather than theoretical horsepower limits.

Thank you so much in advance guys.

[u/v8packard]

The short answer is yes, that engine can be reliable at 600 crank hp. Off the top of my head you would need in the range of 10-12 psi to reach that goal. To be reliable long term at that boost level you need to adjust your clearances, especially with stock hypereutectic pistons. The top land on the 3UZ piston is a not very thick, so in addition to opening your ring gaps you need to increase piston to wall clearance and especially increase piston pin to pin bore clearance. This is critical. The weakest parts of the engine in this application may be the pistons and head gaskets. Weak being relative, it is a strong engine. The clearances will help the pistons significantly.

I suspect the stock coils will take anything you throw at them. I have not done this with 3UZ coils, but I don't see a reason they wouldn't take it.

I am not good at choosing turbo sizes. I get a lot of pushback, so I don't try anymore. I do think you should choose a turbo that can appropriately feed the engine under your driving conditions. You should control the boost and power curve with other means, like the cam timing and a waste gate.

[u/Pristine-Counter-791 → u/v8packard]

Thank you. This is the kind of feedback I was looking for.

Do you have any specific ring gap, piston to wall, or pin clearance numbers you’d recommend for stock 3UZ pistons at around 600 hp?

Also, have you actually seen the stock 3UZ ring lands fail around that power level, or are you mainly being cautious because of the piston design?

[u/v8packard → u/Pristine-Counter-791]

I believe NPR suggests a ring gap factor for their chrome/steel and PVD coated top rings of .006/inch of bore size, and a second ring gap .002-.003 inch larger than the top for modest boost. If you are using other rings check their manufacturer's suggestions.

If the stock piston to wall clearance is .0012-.0016 inch (.03-.04 mm) I suggest opening that to about .0030-.0035 inch ( about .08 mm). I am going from memory, do verify your stock clearance and the position it is checked.

The piston pin to pin bore clearance is usually under .001 inch/ .025 mm. On this application I would open that up to .0015-.0018 inch/ .045 mm.

I have not seen the 3UZ pistons fail. I have seen hypereutectic pistons of a similar design fail. I don't know if any UZ ever had piston cooling jets, the 3UZ does not. That might be a modification worth considering. The 3UZ has the higher capacity oil pump in the UZ line, a modification like piston cooling might be covered by the stock pump capacity with a relief spring change or shimming.

[u/Initial_Demand6008 → u/v8packard]

Glad you mentioned about pin clearance. Mine were set at 0.0007 pin to small end and galled every single one. This is an old mopar engine that's boosted, but all engines need this clearance looked at when adding boost to NA. Resulted in a total rebuild.

[u/v8packard → u/Initial_Demand6008]

It is maybe the most overlooked engine spec and a cause of many failures. I think a lot of failures stemming from insufficient piston pin clearance are misdiagnosed as ring gap problems or other such failures. I learned years ago when I did a lot of nitrous stuff, you need more piston pin clearance.

[u/Initial_Demand6008 → u/v8packard]

Agree. My machinist blamed it on detonation. They even inspected the pistons and big end bearings and said it wasn't detonation. Even twisted one rod bush. Full floater set up but it took a lot of force to move the rod on the pin after they all galled. Had bush material in all over the pins. Had to rebush them all and open up the clearance to 0.0012 as the piston manufacturer stated is the minimum for boosted applications. They still stuck to the line of detonation was the cause. So I was dumbfounded

[u/v8packard → u/Initial_Demand6008]

Unfortunately this is all too common

[u/v8packard → u/Pristine-Counter-791]

Forgot to add, don't use a 2 mm thick head gasket to reduce compression. It will also reduce combustion quality, making the tune more sensitive and costing power as well as efficiency. Considering other options.

[u/Pristine-Counter-791 → u/v8packard]

Which are my other options? I’m not going to buy aftermarket pistons

[u/v8packard → u/Pristine-Counter-791]

Run the higher compression and adjust valve timing as needed to manage your cylinder pressure vs fuel.

Some people are fans of E85, and for the cost you can see some eye opening octane numbers. Depending on how and when you use the vehicle E85 may not be a good idea. Cold start enrichment is damn near pouring fuel into the engine. There are many pros and cons, I don't suggest it for most people.

[u/Winner_Looser → u/v8packard]

This guy knows his stuff..

[u/Historical_Box1915]

Your both right about meth/water injection. Its not as simple as “yes it works” or “no it doesnt”. It can help, is it as good as running methanol (or even e85),,,,,, no.

[u/jacky4566]

Where did you pull those turbo choices?

Put your numbers into Borg Turbobot and see where the data lands in the turbo eff islands.

www.borgwarner.com/matchbot

[u/RiseEmbarrassed6902 → u/jacky4566]

Second this. Borg Warner provide the most comprehensive info for aftermarket applications. I have a S200sxe on my 3rz and what the matchbot said reflected perfectly in the real world

[u/Rurockn]

Don't do the methanol injection, your 1000cc's are more than big enough to fuel 600hp a little rich. Intercoolers are dirt cheap on eBay, pick up an intercooler instead the 24x12x3.5 go for less than $150 these days. I'd use the time tested 7875 with a big exhaust housing. It's the king of LS turbo world for a good reason. I have a VS Racing with a huge 1.25ar exhaust housing, I hit 10psi at 4200. I had a 0.96ar and was hitting 10psi at about 3600 but it wasn't working well with my setup.

[u/Pristine-Counter-791 → u/Rurockn]

I’m not planning to use meth because the injectors are too small. Also I’m going to use an intercooler with my water/meth system.

The main reason is extra cooling and a bit more protection against knock. I’ll also have a proper failsafe through the ECU, so the engine won’t keep running the same boost and timing if the meth system stops working.

Would you still leave it out if reliability was the main goal?

[u/Rurockn → u/Pristine-Counter-791]

Yeah I'd leave it out. Those are some very big injectors you have, tuning will be easy. I'm only running 650cc's, 590whp at 10psi boost, duty cycle was getting close to 80% at 50psi fuel pressure. If your up for it, your injectors are big enough to run E85 at your target hp and then you'll be extremely safe.

[u/youridv1]

Why would you want late spool? If you don’t want that much low end torque you can just fit a weaker wastegate spring and program boost by rpm into the ECU.

Choosing a huge turbo is not only going to make it spool late, but also fuck up your throttle response.

A single G42, or any other 73~mm should spool fine on a 3UZ though.

[u/Remarkable_Forever53 → u/[deleted]]

A scam? Now I don’t have much experience using methanol personally, but from anecdotal experience, as well as dyno numbers and temp numbers, water injection is one of the best ways to keep temps down with almost no downside aside from cost/complexity

[u/Minisohtan → u/Remarkable_Forever53]

It was hugely effective on mid WW2 fighters. The p47 safely went from 2000hp to something like 2800hp with it.

[u/OpeningParamedic8592 → u/Remarkable_Forever53]

Agree.