Post your ITB Setup

[Cheshire Cat]

Yet another Triumph (675R) ITB setup on 3.2SS custom internals etc

[Clay Perrine]

I recently purchased a 935 Style flat fan for my 4.0L 964 motor. So now I can't use the factory intake or throttle body assembly. So I decided to go ITBs, coil on plug, and MS3Pro injection.

I found two sets of BMW K1300S Motorcycle throttle bodies that came like this:



I cut them apart into individual throttle bodies, removed the studs and tapped the stud holes to M6x1.0.

I already had a set of MFI throttle bodies that were so corroded that they could not be saved. So I removed the throttle shafts and linkage from the MFI throttle bodies. I opened the slots on the shafts, and the BMW throttle butterflies fit perfectly. I had to cut the end off the shaft from one of the BMW throttle bodies and weld it onto the MFI throttle body shaft so I had a TPS drive. I pressed the cross shaft bearings out of the plastic MFI stacks for reuse as well.

Using a sheet of plywood, I built a jig to hold the throttle bodies in place with the fan so I can build the linkage and wiring harness before tearing apart the current Motronic setup.

Some time spent with Fusion 360 and a purchase from Send Cut Send, and I now have this:









I still have to make the correct length linkage to go from the crossbar to the center throttle bodies. And to do that I have to buy a M5x0.8 left hand thread die. I considered drilling the throttle bodies for idle air bleed screws, but I can compensate for that with the MS3Pro programming.

This setup is going in my 914 chassis, so it will actually go in with the crossbar at the flywheel end of the motor. I am going to make a throttle cable mount that will attach to the 4-6 side throttle bodies so I can hook directly to the crossbar with no additional linkage.

[Showdown]

Not only is that a really slick modification/conversion, it just looks so bonkers cool!!

[AlKidd]

What diameter are those bike TB's? I ran some from a 750 on a 4cyl Toyota twin cam and they were too big. When you add 6 of them, it could be too much.

[Clay Perrine]

Originally Posted by AlKidd

What diameter are those bike TB's? I ran some from a 750 on a 4cyl Toyota twin cam and they were too big. When you add 6 of them, it could be too much.

They are 48mm. And this is on a 4.0L engine. So I think they are probably really close to the right size.

Clay

[rswannabe]

This is the 3.6 with PMO 46 ITBs in my ‘74. I’m running Megasquirt controlling EDIS ignition coils and batch firing Bosche 30lb injectors. The motor is all stock internals and runs Billy Boat 1.75” headers with heat. I just finished cleaning up the engine bay wiring and fuel line routing. I also modified Zenith carb bases to fit the PMO itb’s so I can run a modified factory airbox. This is the later plastic airbox as the earlier metal ones are too tall to fit on a 3.6/PMO combination without more significant mods to shorten them. The plastic air box will just barely fit as it is about .75” shorter than the metal ones.



Previous dyno testing I’ve done on a 2.2s mfi motor showed the metal airbox improved midrange over K&N filters and gave up very little in top end hp. I also had my 3.8 pmo/Motec motor dyno tested with a modified metal airbox with 2nd 3” inlet to the filter on the back (towards the front of the car) of the airbox. The airbox proved to start to be limiting at over 325 hp and hard to tune and get a steady afr. That motor was comprehensively modded and made in excess of 370 hp, so the airbox was not used and I ran K&N filter hats on it.

The plastic airbox i’m using here has the same 2nd inlet on the backside and this motor should not be making more than 300hp if that. So I think it should work well. I plan to be refining the tune on the dyno in the next few months and will then be able to verify how well/not-well this plastic airbox works in this configuration.

Here’s a pic of the intake on the backside.

[OSC911]

I would love to adapt one of these to my PMOs

[rswannabe]

Originally Posted by OSC911

I would love to adapt one of these to my PMOs

You should be able to run the earlier metal airbox on you 3.0 as well. I bet it would work great.

[H-viken]

Originally Posted by rswannabe

You should be able to run the earlier metal airbox on you 3.0 as well. I bet it would work great.

Do you know if it’ll still fit when using the tall PMO manifolds?

[rswannabe]

Originally Posted by H-viken

Do you know if it’ll still fit when using the tall PMO manifolds?

I cannot answer that definitively. In doing a quick search, I found that standard height pmo manifolds are 82mm and tall manifolds are 98mm. So a difference of 16mm.

I know the metal airbox will fit on PMO’s on a non 3.6. I ran one on my 2.8 SS (3.2 heads). I’m pretty sure that I had standard height manifolds on that. Maybe the metal airbox would still fit with tall manifolds, but I cannot confirm that. I do feel fairly confident that the plastic airbox would fit with the tall manifolds though. Hope this helps.

[H-viken]

Thanks!! I have Webers and PMO tall manifolds, with those the KN filters would not fit. The rear right corner hit the grill

[rswannabe]

Originally Posted by H-viken

Thanks!! I have Webers and PMO tall manifolds, with those the KN filters would not fit. The rear right corner hit the grill

Check out page 7 of my build thread to see the mods I made for the bases and airbox to fit with PMO's.

'74 widebody hot rod build

[H-viken]

Could you please do me a favor and measure from the bottom of the base to the top corner of the air filter box? At rear most portion on the passenger side. I’d like to compare the height with the KN filters

[rswannabe]

Originally Posted by H-viken

Could you please do me a favor and measure from the bottom of the base to the top corner of the air filter box? At rear most portion on the passenger side. I’d like to compare the height with the KN filters

Sure!

The airbox and base do not extend nearly as far to the rear of the car as do K&N hats. So we need to locate the rear edge of the air box for reference. Running a vertical line up from the rearmost edge of the right side of the airbox, that line is 145mm (5 11/16”) from the lip of the engine bay above it.



From the underside of the base to the top of the rearmost lip is 78mm (3 1/16”).



Let me know if you need additional measurements.

[Jjm4life]

William knight 3.45 built by will at fairwinds, with ATpower ITBs. Almost done with tuning but it’s coming back out for a few small adjustments and titanium retainers and valve springs.

[MrBonus]

Originally Posted by Jjm4life

William knight 3.45 built by will at fairwinds, with ATpower ITBs. Almost done with tuning but it’s coming back out for a few small adjustments and titanium retainers and valve springs.

Damn, that thing is a work of art.

[MrBonus]

Clewett ITBs. Waiting on the heater ducts to be powder coated and dyno tuning but the car is running and drivable.

[OSC911]

PMO,Motec M84, SSI/Monty muffler.

[ToySnakePMC]

Love seeing updates and pics on this thread - one of my favorites. Planning to sneak by the shop and see Mr B’s air cooled toy sometime this coming week.

[H-viken]

Originally Posted by rswannabe

Sure!

The airbox and base do not extend nearly as far to the rear of the car as do K&N hats. So we need to locate the rear edge of the air box for reference. Running a vertical line up from the rearmost edge of the right side of the airbox, that line is 145mm (5 11/16”) from the lip of the engine bay above it.



From the underside of the base to the top of the rearmost lip is 78mm (3 1/16”).



Let me know if you need additional measurements.

Thank you very much, that’s all I needed!