I have a pair of Garrett T3's in immaculate shape.

Have big aspirations for off-idle torque.

The plan involves a 360 Magnum in a 3400 pound E-body. Most likely rear-mount.

I've done my reading, but run into a roadblock: The exhaust intake on a T3 is small (2" by 1 1/2"). Exhaust velocity is needed, but, you run into a point where the backpressure is too much. I'm wondering if a 360 is too big. A stock 360 Magnum runs 2" head-pipes.

I halved the engine size to 3.0 liter (to compare to one bank of a 360 with one T3) and searched for T3's. Nothing comes up: at this point Folks go to T3/4 hybrid and other oddball sizing from other Manufactures. I see no advantage to the hybrid on a V8 because the restriction is still on the exhaust side.

Turbo Guys: I'm not looking for 9 second quarter mile times. I want fun-to-drive 500 to 700 lb/ft low 11's, possibly high 10's kind of thing with no lag.

A handfull of names stand out on this Forum with small-block turbos (you know who you are ;)) but I am leaning on all of you for input:

Is this do-able with T3's?

Or, should I get looking at something else?

One thing will remain the same: 2 turbos. (For fabrication and visual simplicity-please don't argue).

I am open to the idea of going stroker/T4 turbo but don't need 900 hp!

Big question, I know, but it's Fryday night, huh?

Check out "turbo lab" they machine holset turbos,with custom wheels

Sorry, one more thing: generally accepted max boost on these is 14 pounds.

After that they drop off and claim "they are over-speeding the turbine and not making anymore power".

I have lots of time to plan this, and remote-setup is not set in stone.

Seen this on a '71 Challenger (GT35's) a 318 cu inch actually :

"T3" is MOSTLY a flange/physical size description. Wheel sizes would be a better indicator of how they would work.
Going rear mount would be a good fit for the smaller exhaust size that a T3 has.... But I think you are asking a lot here from the turbos. "no lag" is not going to happen with rear mounts.
Back pressure is not 100% from exhaust wheel/housing sizing. If the compressor wheel is to small, the turbine wheel spins faster... To the point that the turbine wheel inlet pressure is rising due to centri-force.
I have personally experienced going with a larger compressor- lowering back pressure dramatically. This is why you see T3/T4 hybrids.

There is one upside in the pictured rear mount turbo set up, nearly zero down leg back pressure.

Have you found a compressor map for the turbos you have? Compressor maps are not that difficult to understand and will tell you where in the efficiency range you fall. The T3 maps I have seen, which were for old T3's, looked like they were best suited to engines in the 1.8-2.2 size range, roughly, and that's based on the amount of boost you'd be doing with a little 4 banger. Even with 2 I think you will run out of capacity.

Original Buick GN turbos were T3 based, so they are capable of larger displacement applications. What you have may not be even close. Lots of configurations were made from the basic T3 frame. Also, consider that the GN was only rated at 250hp. Even with one of these turbos, there was lag.

Yeah T3 is only the turbine housing general size and footprint, we need to know what the wheel sizes are an the a/r of the turbine.
A Gt35r with a T3 foot print can make quite a bit of power, last one I had on the dyno was on a 13b rotary, it did about 385 rwhp at around 15 psi. A rotary needs more turbo than a piston motor to make a given amount of power, so two GT35r's on a small block should make pretty big power.

Save yourself a lot of time, join theturboforums.com and post this same question in the Mopar tech section and read hundreds of topics of owners that have done this before you. Spend about six months researching before spending a dime. Understand the pros and cons of each setup (front/rear). 600ft/lbs @ 5,000 RPM is 571HP, this is a reasonable estimate if you keep your RPM's low. Figure out what exactly what your block can hold and what the limits of main driveline components are, there is no secret limit of boost pressure, but the higher the boost the more critical the tune that is required. One T6 BW S475 1.1AR will make all the power you want and more. Look into the economical GT45 t4 setups, we have a very large thread with years of testing on these turbos.

My advice, 1x GT45 70MM, 2.25" off collector merged to a Y-1.75-2" to turbo. 2.5" cold side to front. Make sure everything is wrapped & coated from the header to the T4 flange. This setup will easily make 500rwhp on a 360ci engine. Forget everything you know about N/A engines now, because very little applies. You say you want twins, sure, have you designed a system to return oil to the pan? Twins have twice the amount of failure points on your return system (major downside of remote mount solutions). Only way to get around that is to build a very large oil reservoir/oil cooler system in the trunk and not utilize engine oil. At least then, if a fitting rattles loose (which one will eventually, I lost 6 quarts within a minute or so);, you're out nothing but one or two $200 eBay turbos with cooked bearings.

You will be way, way, way ahead to just run flipped manifolds and stay with a front mount. B/RB Mopars do not have that simple solution.

https://www.theturboforums.com/threads/3...it-runs-9-10-11

my build and experience with turbocoupe T3's on a 383 and then moving up to something better. Short answer is the little Ford T3's would be ok on a 360 if you got them cheap like I did. Rear mount they'd probably be pretty nice, but like everyone else said, it depends what you have. For all we know you've got tiny fwd dodge units!

I went 'cheap' with twin OEM units and ended up costing myself about 2.5x what I needed to spend when I upgraded because I didn't have time to build a whole new kit to work with a big single. To do over again for cost reasons, I'd do a single and in fact have a 76mm T6 for my Coronet someday.

Ok, I'll dig them out and search the id tag and get more info.

Great replies, wow!

I've got a couple of those hanging around. If I picked up another two of them, 4 of them on a 440 ought to be a pretty good match! Wow that would be a plumbing nightmare!

You will be way, way, way ahead to just run flipped manifolds and stay with a front mount

X2

Exhaust casting: .63
Compressor: .48

Screenshot of a turbo calculator that I use:

hmmm 48trim .63a/r, what did those come on originally?

with all of these small OEM turbos, to a certain extent running more boost will put the compressor in a better place as they have pretty narrow upswept maps. For example if you tried 7psi and 6000rpm you'd probably find yourself well off to the right of the map.

That doesn't say anything about the exhaust side.

Based on my own experience I wouldn't want anything smaller than the 60 trim .63a/r that I used on my 383 on a 360 using external wastegates. I've kept those turbos because I've got a 318 in a 72 RR clone that I think they would also be pretty good on.

If I were you I would still run a front mount single, maybe a big T4 would get you by and then you don't have to struggle with the silly talk that a T6 must have 3' of 5" straight off the exhaust, which gets more than a little difficult to package.

Those are aspect ratio casting numbers. They dictate the initial shape of the castings. They can be machined at the factory to fit any wheel, so those numbers don't give any real info about the turbos. You need to measure the inducer and exducer of both wheels to get an idea on their flow capabilities.

See "anthonyfury" the car was built long ago.
http://www.theturboforums.com/threads/303636-Quad-turbo-1968-Plymouth-Fury-(EFI-JY-400-BBM)(Vids-p-6)/page5

A 300zx:

Hope you can read that, I tried copy/paste and it came out a mess.

yup - you can see that even at the 1.8 psi ratio you're calculating (12psi and considering no loss to get the 12psi which is probably not a safe assumption with these) you're just about off the end of the island of 60% eff at 7psi you'd be well off.