Bottom Dollar 4.9 Cadillac Swap Checklist (Page 3/3)
Spadesluck AUG 06, 01:36 PM
I have first hand experience with the regular 4.9 intake to Allante swap. A few wires will need to be lengthened, atleast in for the Fiero format. But it is just about a direct swap. I beleive one connector needed to be changed. If you do a search on this forum there a a few threads about it.

If you get all the Allante stuff...lower intake, upper intake, throttle body, fuel rails etc....there are no provisions for any EGR. It just needs to be tuned out. Simple enough.

Oldjoedad, who is in this thread is a guru on the 4.9 wiring. He could potentially help you out with that as well. Just message him and ask when you get to thst point. I can also help, but he is more knowledgeable on that than me. I do have all the wiring schematics, but they are for what goes to where for a fiero application.
brandon8696 AUG 08, 03:07 PM
8/8/24 UPDATE:

I had a scrapyard out of Arizona on Ebay pull be the entire top end from a 4.5 Allante. 376 bucks after shipping and taxes. Honestly not the worst price considering no yards by me are overflowing with Allante engines, and I didn't want to freight drop an entire engine just for parts.

They have the upper and lower intake, fuel rails, fuel pressure regulator, hard lines, and throttle assembly. The only thing they didn't include was the hose and air box, but my OEM one may just plug right on? When I mentioned my project, I guess they have an employee or an associate that owned a Caddy swapped Fiero and has done the same thing, so they had a good idea of exactly what I needed for the project. Honestly if this place does a good job shipping everything out, I may get the 4.9 from them as well.

If anyone has any suggestions on the best 4.9 I can get for this swap, let me know. I'm assuming I need to stick to a 91-93ish example for a pre OBD ECU and harness? Honestly sort of talking out of my ass until I do a little more research on it.

The project is IN motion though, and I'll be polishing the intake assembly myself, and then painting the 4.9 in a GM Corporate Blue most likely.

brandon8696 AUG 22, 03:43 PM
8/22/24 UPDATE:

The Allante Intake/Top-End is in from Arizona.

They were able to work with me and include all of the necessary fuel line and regulator components.

The next step over the next year will be to gather the 4.9, get the PCM flashed for my needs, and hopefully get the top end polished. I've noticed the intake isn't raw aluminum, but rather coated in something. I may have a professional service strip it, polish it, and clear coat it.


Spadesluck AUG 30, 06:32 AM
Very nice. I would say the hardest parts have been acquired. Now it's just getting it all setup.
Raydar NOV 21, 11:25 PM
Bump? I just discovered this thread.

I forget exactly what changes I made, to make the Allante intake run correctly on a 4.9, but one change I know that will be needed is to import the IAT tables from the Allante BIN to the 4.9 BIN. This is because the 4.9 IAT sensor is in the intake manifold, very near the EGR passage, and the Allante IAT sensor is in the upper plenum.
The 4.9 ECM gets confused when it sees much cooler intake air from the Allante setup, and dumps in a bunch of fuel to accommodate.

For the EGR delete, I think I just copied the "EGR off" values into the "EGR on" tables. There may have been some EGR enable/disable switch parameters that were changed, too. It's been a few years.
I saved all my tuning changes for this, as well as for when I swapped in the manual trans. I might be able to dig up a tune for you, if you can get it programmed. (I don't do chips, but all my files are free for the asking.) The 4.9 requires a 27SF512.

As far as 4.9-to-Allante wiring, the only thing you will have to change, other than extending wires, is the TPS connector.
The wiper on the 4.9 TPS is the center pin on the connector. The wiper on the Allante TPS is at one end. Don't ask me which end.

I retained my 4.9 ECM. I tried running an Allante chip in it, but it did "funny things". I was hoping that the Allante tune would be happier with the manual trans, since the Allante ran the F7(?) transaxle, which was a bit more primitive than the 4T60E. Kind of an interim between the 440T4 and the 4T60E. But, no bueno.

[This message has been edited by Raydar (edited 11-21-2024).]