Topic: 4.0 throttle body questions

[ddrongowski]

Okay I have a stock throttle body on my 2.5 right now. I also have in my box of things a stock 4.0 throttle body from an XJ and a 63mm bored throttle body unit. Three throttle bodies and only one engine . So what questions do I have?
1. Do I need a spacer to use the 4.0 throttle body?
2. Do I need a spacer to use the 63mm throttle body?
3. If a spacer is not needed is there an advantage to using a spacer?
4. From what I have read the 4.0 throttle body seems to work better on a stock 2.5m then the 63mm unit. Is this true?
5. What are the gotcha's in installing each unit?

Thanks

Specs
1991 YJ, 2.5L with k&n filter, restrictor in filter box removed, electric fan, 31" tires, stock 4.10 gearing, 2" skyjacker lift. I have no problem running 70MPH on flat freeway in 5th, but inclines slow me to 60-65mph.

[Jeffy]

1) No
2) No
3) Moves the torque band lower.
4) Haven't used a 63mm but the 54mm works fine.
5) Make sure you swap the IAS housing over as well as the IAS motor.  Also make sure that 4.0L XJ TB is from a 4.0L HO and not the 4.0K Renix.  If it's a post-96 then you will want to plug the MAP port on the side of the TB.

[ddrongowski]

Thanks.

The 4.0 TB is supposed to be a 93-95. How would I tell if it is the HO or Renix? I did not realize there was a difference.


EDIT: I think I already have my answer. The RENIX has 3 mounting holes, and the HO has 4 mounting holes (along with other things).

[sharpxmen]

5. also use the throttle position sensor from the 2.5 (my understanding is that they are different).

[mrcabinet]

Use the 63mm and bore the intake manifold to match - either by grinding or with a hole saw. There is a marked difference in performance compared to the 54mm.