Topic: 4.0L TB SWAP AIS housing question

[Nicks92jeeper]

I believe that I used the 2.5 housing. I tried the 4.0 but my rpms were at about 4500 rpm and I though that was a bit dangerous. So I used the 4.0 throttle body with the 2.5 sensors and AIS housing. This was last year that I did this mod and my brain is shot right now. I would basically say try the 2.5 housing with the 2.5 sensors. If that doesn't work then try the 4.0 housing. Make sure that you have a good seal as well so no intake leak.

[Nicks92jeeper]

Found a picture and I took everything off the 2.5 and put it on the 4.0. This picture also shows how much you will gain if port math or whatever with the intake manifold to match the TB. It would be a noticeable difference in my opinion. The 2.5 is on the left and the 4.0 is on the right. the second picture shows a faint line of the potential size it could open up to. the third is opened up. I used a drum sanding bit in my drill press and it made fast work since the intake was out.

[sharpxmen]

Found a picture and I took everything off the 2.5 and put it on the 4.0. This picture also shows how much you will gain if port math or whatever with the intake manifold to match the TB. It would be a noticeable difference in my opinion. The 2.5 is on the left and the 4.0 is on the right. the second picture shows a faint line of the potential size it could open up to. the third is opened up. I used a drum sanding bit in my drill press and it made fast work since the intake was out.

that's not a 4.0 on the right btw, it's a bored out 4.0, the stock one tapers on the bottom (similar to the 2.5 but larger diameter) - the machining job is not that great but at least whoever did it stopped before the butterfly to prevent getting it out of spec when the throttle is closed - you got a bored out t/b to 60mm for $15 which is a really good deal.

[Nicks92jeeper]

Actually I bored it out with the drum sander on a drill press and just wanted to get it good enough. You gunna make me cry! I bored it out a bit on both ends and after this picture I smoothed out the sides so they were smoot and consistant. I like the fact that you noticed though!

[sharpxmen]

Actually I bored it out with the drum sander on a drill press and just wanted to get it good enough. You gunna make me cry! I bored it out a bit on both ends and after this picture I smoothed out the sides so they were smoot and consistant. I like the fact that you noticed though!

that's actually a pretty decent job for first time and on a drill press

reason i notices is b/c i made a few myself bored out to 64mm
turned out like this (last ones i made, i busted a few trying to get largest bore but neve been able to go past 64mm)





(not trying to sell them, have none at the moment - just in case someone will think i'm pimping them out)

[bukdwn]

Here's what i ended up doing. I removed the 2.5L housing and re-installed the 4.0L housing. The 2.5L housing on the 4.0L TB did not idle the best.  The idle would take a little longer to come down to normal idle. Everything in this jeep has been changed as far as a full tune up. The engine runs like a top! At cold start up, the TB with the 2.5 housing would be around 17 to 1800 RPM's. With the 4.0 TB housing installed the cold start is around 18- 1900 RPM's.  I need to install a new air filter system, i can tell with the stock air box top unclipped  for straight threw air, that it comes up in rpm's a little faster.    So, if your having problems with your idle with this mod, try installing the 4.0L  housing!  Thanks for all the info and the fact's forum! i really appreciate it.

[sharpxmen]

how's your air filter? also, do you have lot of blow-by?

[bukdwn]

SHARPXMAN, As far as the air filter, I have the stock air box and filter. The filter has been changed in the last 300 miles.  forgive me but i'm having a brain fart!  What exactly do you mean buy blow buy?

[dwtaylorpdx]

Blowby is the gases coming from the crank case. (Usually from around the rings)
If the crankcase vent is plugged (Small brass fitting on valve cover) it will blow a
lot of vapor where it does not belong. Which will gum up the IAC and the passage it sucks through.

Dave

[sharpxmen]

Blowby is the gases coming from the crank case. (Usually from around the rings)
If the crankcase vent is plugged (Small brass fitting on valve cover) it will blow a
lot of vapor where it does not belong. Which will gum up the IAC and the passage it sucks through.

Dave

correct, will also mess with your idle that's why i asked (and that's regardless if the small vent is plugged or not, too much and will blow thru both).

[Nicks92jeeper]

When I did the head gasket I examined everything to see if there was any blockage and the vents in the valve cover was completely clogged so I opened them up again. The reason I looked was the air filter was coated in oil so I knew something was clogged up but I didn't notice anything on the idle as I did a lot of mods at this time.

[Nicks92jeeper]

@ Sharpxmen. Those are some real pretty Throttle bodies! You did a very good job on boring them out.

[Bounty Hunter]

Your high idle at startup sounds like it has nothing to do with the IAC, but more likely a vacuum leak.  It comes down as the IAC adjusts for the vacuum leak in an attempt to correct the high idle.

Really, you should prolly run the 2.5L IAC housing and plunger.