IAC options?

**dyeager535** · 10-01-2013

So taking my sweet time, getting around to mocking up the throttle body on my Olds FI intake. It's a BBC throttle body, I'm planning to build the motor up enough to get some use out of it's larger bores. Running into fuel rail clearance issues, on both sides actually. Think I can work around the throttle cable issue, but if I could get a smaller IAC, or an adapter that moved it vertical, it would allow some options in intake to TB adapter thickness. The LS-series IAC's look the same as the TBI ones. Anyone familiar with an IAC that is shorter but compatible? Will be running a 1227727 if it matters. I'm not even sure a 90* adapter would solve the issue. May have to live with the 2" spacer, but that creates problems of it's own. Due to intake design, not going to allow me to offset the throttle body to gain clearance either.

**EagleMark** · 10-01-2013

The BBC IAC already saves some room... there's also a TPS with plug that points up...

**JeepsAndGuns** · 10-01-2013

I ran into the same problem when I went to MPFI. A tbi throttle body without the injector pod was too wide and would hit my fuel rails. After much looking and playinging around with different ones, I ended up using a slightly modded vortec throttle body.

**dyeager535** · 10-01-2013

You have any pictures of that? Like this? http://www.ebay.com/itm/Vortec-96-20...ht_1004wt_1399

I want to keep the stock air cleaner, so the BBC TB obviously helps in that goal, but adapting the air cleaner to a different TB might be easier than trying to force the BBC TB to fit. Apparently that won't work though, I'll have to measure, but the intake I'm working with is cast very goofy, there isn't much metal to work with, the 454 bores are almost too large to fit. Hard to tell from this image, but its kind of like a cylinder in an engine block...too much boring and you end up hitting "air". http://www.gmcmhphotos.com/photos/40...ion/p3687.html It's the nearest intake, you can just barely see the passages cast in it. Unlike the TBI intakes of later years, the passages for vacuum are cast into the mounting flange of the intake, vs being all in the TB.

So far it appears TPS is no issue, it's just the IAC and throttle cable stud. If using the BBC TB, think I can just re-do the throttle cable stud so it's inboard of the plate it mounts to.

**JeepsAndGuns** · 10-02-2013

Looks to be the exact same TB that I used. I had to cut off that little arm and trim it a little. Also, the V8 ones are already 75mm, they just taper in under the throttle blade. I had a local machine shop remove the taper from mine.

You can see some pics in this thread: http://www.gearhead-efi.com/Fuel-Inj...Getting-closer

**dyeager535** · 10-03-2013

1001132155.jpg 1001132156.jpg

Sorry for the picture quality, terrible phone is all I have to take pics with.

I suspect if I am even able to fit the 75MM throttle body, I'd end up shifting the problem from needing a thick one-off TB adapter/spacer, to having an even more odd TB adapter/spacer AND having to re-do the air intake/air cleaner setup. With the 1.5" "spacer" in the pics, it JUST barely fit the hood. Enough that if another set of motor mounts is slightly different it might cause issues. Maybe I should just make my adapter/spacer out of a 2x6? lol

You made me think of something else though...I wonder if I could just have the TB "pad" milled right off this intake, and start with a flat surface? That would solve pretty much every issue. It's a single plane intake, so if it's cast as I suspect it is, that may be viable, although no idea what that would cost me to have done vs. the adapter/spacer I will need otherwise.

**JeepsAndGuns** · 10-03-2013

I had some hood clearance issues with my setup too, the intake I used was taller than my old one. I made a adapter for the top of the TB and used a low profile carb bonnet. From the bottom of the TB to the top of the adapter is 2 3/8in.
You can see pics here: http://www.gearhead-efi.com/Fuel-Inj...ing-here/page3

You dont have to use that elbow or air inlet like I did, you could probably use your factory air cleaner, assuming that the underside of it clears the throttle body and related parts. This is just the way I went to convert that TB to a more common round inlet size for a much larger choice of air intake elbows.

Do you have a picture of your intake without the TB or wood plank on it? Just curious of what we have to work with here.

**EagleMark** · 10-03-2013

If it's just the IAC? You could move it with something like this...

**dyeager535** · 10-03-2013

This is just as clear as anything I can take with my phone: http://i200.photobucket.com/albums/a...7700004-12.jpg

The top intake is the one I'm dealing with. You can see how the bores are "raised" in relation to the areas around it. Fitting a single bore TB to that would require a complex adapter.

That's why I'm wondering if machining that whole area flat would be a better idea.

**dyeager535** · 10-03-2013

Who makes the one you picture? Ones I found are $150+. Not sure how much machining that would pay for.

Depends on what I end up with for height...throttle/cruise/TV cable connections can be an issue too.

**Fast355** · 10-03-2013

This person did a swap years ago and has a few pictures left.

http://www.grimers.com/vehicles/olds/403efi/index.html

**EagleMark** · 10-03-2013

Originally Posted by dyeager535

Who makes the one you picture? Ones I found are $150+. Not sure how much machining that would pay for.

Depends on what I end up with for height...throttle/cruise/TV cable connections can be an issue too.

I just looked at your intake picture as well as trying to follow your need to raise TBI by 2 inches? Well make the 2 inch adapter and drill a hole, then tap for an IAC into existing IAC passage!

When I had my IH 345 intake machined so the bores were straight through and matched with TBI and adapter cost $100.

http://www.gearhead-efi.com/Fuel-Inj...1&d=1328417373

EDIT: From the link FAST posted it looks like those IAC passages were actually EGR? So what, looks like it would work fine?

**dyeager535** · 10-04-2013

The guy that did that 403 EFI swap used the V6/SBC throttle body. No mention in that article about IAC, and his adapter doesn't look very thick either. I see what you mean Mark in regards to the BBC one saving space. I wish the guy in the link had more info.

I did some measuring, came up with a spacer height that will appear to work. IAC clears the rails, throttle shaft is out in the open, air cleaner won't hit the hood. Just under 1.5" thick, luckily don't see any reason a spacer won't work after mocking it all up, and that's not MASSIVELY thick. I think I understand what you mean about drilling for IAC, you are talking about just completely relocating it, right? At this point other than some material cost, a spacer of any thickness is going to be somewhat pricey, so its either pay for the thicker adapter, or drill tap a fair bit to relocate the IAC. I don't see an "easy" way to relocate the IAC.

I wish GM had gone with a TB bolt pattern on this setup that was "standard", an off the shelf solution would be a lot easier. It's still going to be a large chunk of AL! Guess this is my reward for investing my time in an extinct brand. :)

**EagleMark** · 10-04-2013

Yes, relocating IAC to the spacer where EGR passages are?

**dyeager535** · 10-04-2013

I can only envision a complex solution...getting filtered air would be the hard part. I guess as the aftermarket solutions, a hose barb threaded into a hole with filtered air from air cleaner housing, drilled seat for the IAC pintle and bore for the IAC housing to bolt to. I suppose not overly complex, just getting the right bit to cut the pintle seat, and a bit large enough for the IAC to sit flush.