I am using a throttle body from a 91 on my car. For hood clearance reasons, I have limited space above the intake for the plenum. I am also putting this on a BB C3. This poses clearance problems with the thermostat housing.

I don't have the C4 plenum or intake but I know that there is a triangular port on the plenum that is ported (through the plenum) to a small tube that goes to (don't know). Also, I know there are two small holes in the plenum right behind the throttle body ports that are open to the (lemme guess, the EGR)?

OK, getting to my question. Can the IAC be relocated?

wow... I kinda doubt it.

The IAC is located there to control idle air. I don't know how well it would react to being in another location...

I'm with Bogus, I don't see how...

It's a motor that pushes a pintle in and out to regulate air flow at idle.

Thanks for the replies. I am aware of the function of the IAC valve. However it is an air "bleed". Very low air flow, only with the throttle plates closed. Carbs have had the same idle air bleed circuit for years and some (air bleed actuators) are even remotely mounted similar to what I am talking about. Also, some people relocate Ford IAC's but I am not sure of the difference.

Any ideas about where the IAC gets its air? Are the two holes in the plenum for EGR?

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OK, I see where you're going. If it draws its air from a remote source you can remotely place it.

No, the source is where you mentioned, and the inside of the TB is shaped like the pintle as it seats into the TB.

I don't know how the Fords work to say.

Of course is can be relocated, just fabricate a small manifold ... a block w/ some ports on it to hook yp a hose/line and the IAC

It really doesn't matter a whole lot if it's in a different location.

You can also relocate the IAC somewhere on the main plenum chamber, the only reson for it being in the TB is that you won't need a second fitler or some elaborate system to pull air from behind the filter, and machining the TB for an IAC is the cheapest solution vs. machining different parts/needing more parts.

The plate idea appeals to me with the IAC mounted somewhere else. I would still like to know what the two small ports in the plenum are used for. I assume one is for EGR.

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What happens to the holes in the TB where the IAC draws air, and where the IAC used to sit?

What I was thinking was to fashon a nut that fits in the original IAC and put a hose off of that to a remote location for the IAC.

I'm thinking to get a stock TB that is trashed and cut out the IAC portion to use as a manifold.

Seems involved no matter what is done.

Don't know if this is any use to you, but.....

I just installed a HSR intake with custom plenum on my vette. The plenum is low to allow hood clearance, but there wasn't enough room for a thermostat housing under the throttle body. I removed the little torx bolts, then removed the IAC housing/water jacket from the bottom of the throttle body. I then removed every little bit of aluminum that wasn't needed for the IAC housing with a dremel. When I was done I had an IAC housing only that was held on to the bottom of the throttle body with 3 bolts. I also had to shorten the "seat" of one of the 4 bolts that held the throttle body to the plenum to gain a little more clearance. It worked for me, it is amazing that about 2/3 of that piece on the bottom of the throttle body was for the water jacket and not the iac valve housing.

As a side note, I have heard of people being able to completely eliminate the iac and make up for it with the tune. I have no experience with this, but I saw a couple of different threads on CF about it roughly 6 months ago.

I recall that both holes in the plenum bottom are for egr, the little runner tube on the drivers side is for evap/pcv, the middle hole on the front face of the plenum is for IAC air.

The TB I have uses filtered air from in front on the throttle plates for the IAC. The IAC opens/closes a path from there to behind the throttle plates (into the plenum).

I kind of confused things asking about the other ports in the plenum at the same time. I'm pretty sure I won't need them. I have no EGR and PCV can be directly ported to the plenum.

I don't know how much room you need but doing what I said above gave me alot of room I didn't have. My TB is an '89, not sure of the differences year to year. By removing the little torx bolts you can take the housing off and see exactly what can be removed. Easy to see once you look at the inside of the housing under there.

"I don't know how much room you need but doing what I said above gave me alot of room I didn't have. My TB is an '89, not sure of the differences year to year. By removing the little torx bolts you can take the housing off and see exactly what can be removed. Easy to see once you look at the inside of the housing under there."

I am putting this on a BB C3 and the ptoblem I have is that the thermostat housing is pretty much dead center on the BB manifold (the C4 is to the side). So that means my IAC port interferes with the thermostat housing. I don't really have any clearance issues with the reast of the IAC plate. That seems to be the way this project is going, everything in the same place at the same time

I have a stock TPI thermo housing, they are squashed down pretty far and don't require a ton of clearance. They actually taper a little from back to front to allow even more clearance. I didn't use it because the bolt holes on the HSR intake were in a different location so it made the stock thermo housing point towards the passenger side front but the radiator has the stem on the drivers side front. It is a little rusty but could be cleaned and painted. If you think it would work for you send me your address and I'll send it to you. I have no clue if a TPI thermo housing will fit a BB intake or not, but if you happen to know or want to try it pm me your shipping address.

My only other idea would be for you to remove the IAC and IAC housing and make a flat piece of metal plate to replace it. You might be able to tune the car to not need an IAC at all. Do some research on that if it would give you the clearance needed, I've seen threads on CF about that. Most of those members are probably here now.