I don't think the 01 750 tb's will be enough. The 420a is 2.67 times the displacement (cams play a major factor in airflow, so I'll compare against displacement only). So, at 7k RPM's in the 420a, you'll be pulling enough air to match the 750 at over 18k RPM. The 1k would be about double, so 7k RPM's will match to about 14k RPM's, which isn't far off from their redline. The busa, though, is a lot closer, as the 420a is 1.54 times bigger. At 7k RPMS, the 420a's pulling the same amount of air as the busa at 10,780 RPM, which is damn near redline (10,600 in gears 1-5 IIRC).

Personally, I'd go with the busa throttle bodies.

You have the right idea about mounting the vertically, though, and your best bet would be to use a tubular intake (a hacked obx, or custom). I don't know if the 01 750 tb's have the secondary butterflies on top, but they're not needed unless you want the fast idle (which you'll have to program the MS to handle). The busa tb's have no secondary butterflies for the fast idle, only a cable, but the 1k's do (05-06 I know for sure, other's, I'm not sure). If you wanted to have a fast idle with the busa TB's, you'll have to go old school and have a pull cable. Since you'll have ZERO idle control with the busa TB's, you may look into the k5/k6 1k TB's to have that functionality.

Since they're all setup with vacuum lines that run together for a MAP sensor, you got that covered; however, you'll have no vacuum source for your brake booster or any other actuator controlled with vacuum. You'll probably have to build a vacuum reservoir to help out here.


This is only speculation below, so take it with the weight of a grain of salt:

the only other issue I see is the placement of the injectors on the TB's. They're designed to squirt almost directly into the cylinder, much like factory placement on the 2gnt, except from the bottom instead of the top where the cut-out is on the intake port. If you have intake tubes that curve roughly 90* to mount the TB's vertically, they'll be squirting at the pipe instead of into the intake port. It's not like perpendicular or anything, only like 30-45 degrees, but I don't know how much affect this will have if they're 5 inches from the intake port. The airflow may just cary the fuel right into the cylinder, though, and not make any difference at all.

~Luke
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1969 Cougar - 11.91 - 380HP
2007 GSXR 750
1999 OZ - SOLD - 15.26 NA - 14.71 on 75 shot