making IAC for ford TB mounted on 3500 plenum

[Froggx]

I know this might be an awkward topic to look at, but I'm having a hard time figuring it out. The 3500 plenum doesn't have quite the provisions for setting up idle air control that the 3400 one did. Also, the GM stuff naturally won't bolt to the Ford TB. So my question is how can I go about adapting the IAC from the 3400 to this 3500/ford hybrid thing. There is also the possibility of using the IAC off of a Fiero as I have 2 fiero TB's and IAC's lying around, problem is I cannot tell at all how these things work. I'll have pictures up tomorrow thanks.

[RacerX11]

RE: making IAC for ford TB mounted on 3500 plenum

I can't remember, is the Ford TB you are using the late-model 65mm one without provisions for a Ford idle control valve? My BBK Ford 5.0 TB has the Ford setup on it, and I have designed an adapter block to mount the GM IAC to the Ford TB (I just haven't built the block yet). The late Ford TB's had a seperate idle valve, so you would have to rig up something else.

Are you using EGR? There are several open ports on the 3500 plenum (I can't remember off the top of my head what they all do). You should be able to use one of them, and make a block of aluminum that mounts the IAC.

Marty

[Froggx]

RE: making IAC for ford TB mounted on 3500 plenum

Yeah, my throttle body is the late model one with no provisions for idle control valve. My EGR, PCV, and EVAP ports are all open on my plenum since I'm not running any of those through it. I was thinking of adapting to one of those. The thing is, I'm not entirely sure how to make an adapter block. All I have in terms of IAC hardware is the pintle assembly thing then the passages on the throttle body. Sorry, I didn't have a chance to get pictures today.

[RacerX11]

Do you have the early threaded IAC, or the later ones with the O-ring and mounting flange? It is far easier to make an adapter block for the later IAC. The one I designed for the Ford just uses three stepped holes to mount the IAC, just like the stock TB. Here are some crude drawings of how to do it. I'll try to get some accurate dimensions for the hole sizes, and maybe Brad can draw seomthing up in CAD.

One picture shows the adapter block with the IAC mounted, while the other is just the adapter block. I am making mine out of a piece of 1-1/2" thick aluminum.

Marty

[bszopi]

Get me some measurements and I'll see what I can do. Doesn't seem like it would be that hard of a thing to draw up or made for that matter.

[Guest]

Or you can buy ione from Holley, that uses the older GM IAC (TBI type) and bolts right onto the fird TB/or Ford IAC adaptor.

[RacerX11]

Do you have a part number for the Holley adapter? I looked for it last year, but couldn't track one down. This wouldn't do Frogg any good, since his TB doesn't have the Ford mounting provisions.

Marty

[Froggx]

It would still be interesting to look at the holley adapter if there are any pictures or anything. Looking at this design, it doesn't like incredibly hard to do. Let me go take some pictures of what I have.

[Froggx]

The hole in the throttle body near the TPS is what I assume idle air went through in the ford setup.


I can send air through the ford hole or any of these 3 other gaps (egr, evap, or PCV)


A picture of the fiero IAC with throttle body still attatched. It's kind of scary so I think I may avoid it.


Here is what the IAC, uh, thing I have looks like, I think it's the o-ring type you mentioned. It was hard to get a picture so I took 2.

[RacerX11]

I think that hole in the TB used to have a pressed-in tube to hook up to PCV or something else. They used an IAC valve mounted remotely in the late engines.

Looking at the plenum, the EVAP port (I think that's the rectangular one with two mounting holes) would be your best candidate. With an adapter block mounted there, with the IAC pointed vertical, you could use the hole in the TB (it is upstream of the throttle plate) to source filtered air to the adapter block via some 3/8" vaccum hose. Is that TB casting thick enough around that hole to tap it for a 1/4" pipe thread for a barb fitting?

I'll see if I can't draw something up to mount to the 3500 plenum.

Marty

[Froggx]

rectangle port with 2 holes is egr, round one next to it is evap, and big round one near TB is pcv from my understanding. I agree the rectangular one would be easiest to mount. The hole in the TB (pcv now I guess) vents after the throttle plate (unless I looked at it wrong, I'll get a pick when I pop the TB off again). I was thinking just fitting one of those mini air filters that commonly go over pcv's that vent to atmosphere in order to source filtered air. I'm using a MAP sensor instead of MAF so I don't have to worry about messing anything up in tuning by going that way.

I drew a VERY BAD drawing of what I think you're talking about.

[RacerX11]

That's pretty good. The only changes I would make would be to feed the clean air source 90 degrees from what you have it (out towards the screen in your picture), and also have the feed at the top of the pintle, with the manifold tube exiting from below. I'm not sure if this would affect flow or not, but that is the direction of airflow past the pintle in a stock setup.

You can tell by your 1st picture that the hole feeds into the TB prior to the throttle plate. I would prefer to use a short section of hose into the TB versus a seperate mini-filter just for simplicity sake.

Marty

[Froggx]

more like this you mean?

[RacerX11]

Yep....pretty much. I just got the dimensions of the holes and sent them to Brad...he will probably get something drawn up and pretty (at least prettier than I can do).

Marty

[bszopi]

Ok, I got the preliminary design drawn up. I still need to dimension it and draw up the air ports, but my wife just got home from work, so it's time to spend some time with her...