Borg Warner turbo in a Turbo Buick!

It only takes a rod to let go and the motor is junk, the new parts are worth saving your money for. Once the stock stuff let's go you can damage just about everything just look at Nigel post..
The rods wont be the mechanical failure first...
I wouldn't be so quick to disregard the 3 bolt, presently a limited number are available from (call the number and ask for Sam). These are from the same batch of housings pictured in post #20 of this thread.

At the recent Lorenz Performance and Racing open house two GN's with 3-bolt BorgWarner EFR-9174's were dyno tested:

First car was John Schmidt's, e98, GN-1 stroker with rollers and GN-1 heads and matching intake, to the rolls it made, 822 Ft-Lbs @ 3,800 RPM and 659 HP @ 5,200 RPM on ~29 psi, this car previously ran a 9.97 @ 135 with this set up but pig rich. Leaning the car out a bit while on the dyno bumped the power from 600 to 659 HP.

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Second car was Bryan Lynch's, (phoneguy) stroker, pump gas with alcohol, TAI class legal, to the rolls it made 856 ft-lbs @ 3,700 RPM and 640 HP @ 4,500 RPM

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Bryan's feedback about boost response is that it comes up on boost very fast!

Another recent development (Thanks to GEE-M racing) is true twin scroll headers!! These headers were on display at the 2018 nationals along with a BorgWarner EFR 7163-G turbo. These headers should accommodate all EFR twin-scroll turbos and also many of the BorgWarner AirWerks turbos.

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There are now available options for 3-Bolt, single scroll four bolt, and true twin scroll four bolt.
For some reason I am just now coming across this thread... I went 9.72 @139.92( Bowling green 2018 , off the trailer) with the 3 bolt EFR 9174 at 27 psi through most of the pass and touching 29 at the top of the track. The Turbo hits HARD and FAST, and the recirc valve works very well. I am not sure if there are any of these still available but you could do much worse by not looking at one... The way that most of us look at turbo sizes , this equates to a 67.6mm by 65mm. Pretty impressive to run almost 140 mph on a 65 exhaust wheel. Many thanks to John Norton for making this happen, and for donating this to the Nationals. I own the first one that was built as I won it in the raffle.

What ever came of EFR bolt on turbos for the GN's?

Looks like this never got produced and online only exhaust housings flanges in..
T3, T4 and one V Band at .85.