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Great news! Any power gain/loss?

I have one more idea in mind before i look at idf manifolds, but if you end up making any more sets, i may be interested.

Do the spigot flange couplers for the gsxr TBs have a little ring lip in them to fit into the groove on the bottom of the throats in the throttlebody casting? maybe that doesn't make sense...idk

It's hard to say if it's faster or slower, I still need to fit the stacks to make a fair comparison.

yes the spigot flanges have the "ring lip" that fits into the groove on the TB, without the clamp its a complete bitch to take the flange off, and with the clamp tightened up it's damn near impossible to pop off.

I went from 38 to 40mm, I kinda was expecting to lose some vacuum but so far it seems I gained some. This is turning into an interesting little experiment.

That sounds very promising. Do you by chance know if there are different sized spigot flange couplers? or is is one size fits all gsxr?

There are a whole lot of different sizes but mainly 2 different ones for us

I'm using the KHS-004's and they will work on your TB's (I got mine off amazon for about $15 each shipped)
the M-VM38-200K are similar

and for the guys using the later 600 stuff as well as the 42mm TBs the M-VM40-200K ones should work.

I just checked the valve lash (second time in 10K miles), and it was good, so I went for a drive and the fuel filter clogged again, this is getting old. I'm guessing I stirred up all the crap in the tank and my 10micron filter is doing its job...just a little too well, FML.

hm those look like they would almost bolt on non-3 stud heads...

Piledriver wrote:hm those look like they would almost bolt on non-3 stud heads...

The IDF mani's I'm using can bolt onto 3 or 4 bolt heads

I'm curious if you could use those AS manifolds....direct to head, or perhaps as easy head flanges for tubing.
The TBs don't care if they point up.
(option on a 914, anyway)

IIRC the GSXR TBs are just about the exact same spacing as the ports.

maybe, and the stock gsxr injector angle then would be just about perfect too

So I got a little bit seat time today, I'm really liking these 40mm TBs. I now have a lot more vacuum to work with, so much so I'm going to reindex my maps. Still dialing in the tune and trying to clean up the idle but it's a very drivable setup.

so I paid a little closer attention to my MAP readings, my normal 70mph cruising speed on the freeway used to be at 85KPa, not it's 77KPa and the MAP signal is rock solid. I'm still sorting the idle but at 1400 rpms it is 59KPa before the best I could get was 62-63. So I definitely have more vacuum with these bigger TB's, they sound different too, better.

Looks effing clean!!!

Thanks RD, I'm really feeling the fuel system.

Too bad their so tall..... Other then that, awesome! I'd there a way you could t urn those 90* and point them at each other with a shared plenum? Lots of fabrication, but you could use the stock fresh air intake and close the lid.... Maybe


Sorry, that is a sh!? load of work.... I don't know what I'm thinking.

Nice work as always, Ninja.

Too bad their so tall..... Other then that, awesome! I'd there a way you could t urn those 90* and point them at each other with a shared plenum? Lots of fabrication, but you could use the stock fresh air intake and close the lid.... Maybe


Sorry, that is a sh!? load of work.... I don't know what I'm thinking.

Nice work as always, Ninja.

Roverjosh wrote:Too bad their so tall..... Other then that, awesome! I'd there a way you could t urn those 90* and point them at each other with a shared plenum? Lots of fabrication, but you could use the stock fresh air intake and close the lid.... Maybe


Sorry, that is a sh!? load of work.... I don't know what I'm thinking.

Nice work as always, Ninja.

it is what it is, the motor likes the longer intake length. On my notch, I'm willing to sacrifice not running a engine cover (I have a bulkhead sealing out the heat and noise behind my back seat). You could use a type 3 IDF manifolds and shorten the v-stacks way down, it probably would clear the lid(if your running a type 3 motor). Piledriver wants to do the TB's in a sidedraft configuration with a common airbox, he also has a squareback so it's more smart to run the lid on it.