Engine Swap?

[covert420]

Now please say if you are speculating or if you know what you are talking about when you respond to this thread...

Is it possible to drop a 4.6L Northstar in our engine? I know the 4.6L bolts onto the same transmission in Cadillacs, but I have heard that the computer mechanics just dont work together. The person who said this said a 4.6L only works with the transmission bolted onto a 4.6L, and vise-versa. If this is the case, then I guess a whole engine/transmission swap would be possible, but that is pricy.

Does anyone have any information on this stuff?

[kobalt]

This has been discussed before, try the search function and look for "4.6" but to answer your question briefly yes the transmission is the same and will bolt right up

[JimW]

Electronics would be different, PCM as well....but yes, do a quick forum search, this had come up a few times.

[covert420]

It does not seem if anyone truely knows about the electronic/computer internals...

[Custom88]

because no one has done it. You should be able to do this with the PCM for the 4.6 and the engine/accessories obviously. I don't know if the gear ratio is different between the Aurora and the Cadillacs though. The Caddillacs might not be 3.49 or the 3.73? ratio that the aurora uses. If not you'd need a CUSTOM PCM program.

[JimW]

The STS has the same gear ratio as the Autobahn Aurora (3.71:1)

I suppose it would be cheaper/easier to get the 4.0 V8 to get to 275-300bHP for less then swapping engines.

[Custom88]

jimw said:

The STS has the same gear ratio as the Autobahn Aurora (3.71:1)

I suppose it would be cheaper/easier to get the 4.0 V8 to get to 275-300bHP for less then swapping engines.

Indeed. I would venture to guess that an afermarket PCM would do the trick. I have afeeling the PCM in the Aurora for both the 4.0 and 3.5 are tuned excessivly conservative.

[covert420]

True.. but rather than unlock a 4.0L, why not unlock a 4.6L? Everything doable should be able to be transfered to the 4.6L. Intake, Throttle Body, Exhaust, DownPipe, Coated Headers, they should all bolt right up to the 4.6L as well. I was indeed thinking about unlocking the 4.0L first, then saving and ONE DAY making the swap... But since I am saving so much money likely, the swap is just so darn tempting.

I wonder if anyone has fully unlocked a 4.6L? The DOHC should produce some big numbers if it is able to breath properly and is tunes right. I could see it putting out 350HP with a completely custom full exhaust and intake and some solid tuning.

[JimW]

That is most definitely possible, but their are limitations to the amount of bHP that the 4T80E can handle. Anymore then 300-310 HP on the tranny and its going to go prematurely. It could really use an LSD and a nice shift kit.

[covert420]

I have never heard of a 4T80E having any issues, and I know there are atleast a few Caddy's with Intakes and Exhausts, and they weigh a lot more. I think the transmission is safe, but an inspection and shift kit is almost a must.

This gets me thinking... What about the NorthStar with VVT? It produces numbers like 320/310 stock. Its only been mounted to Caddy RWD applications though. I wonder if it would mount similarly to a 4T80E?

[JimW]

That would be really sweet if the trannys on the new Caddys could work in a FWD application..I think its called the 5L50 or something like that...totally new hardware.

[Aurora40]

As far as I know, no one has done this mod. So it's all speculation. It's possible the stock computer would work if the sensors all gave the same inputs, and the injectors were oversized the right amount (or fuel pressure was higher). No one really knows, though.

It's a lot of expense for 25-50hp, though. I agree it would be cool, though. I'd go with the 275hp motor. The torque on the 300hp motor is less up until about 5,000 rpm. And with the new more accurate SAE ratings, the difference is narrower, 275hp vs 286hp. I'd take the extra torque.

The RWD VVT Northstar is practically completely different. And how the heck would you control the VVT part? You'd need serious control system mods.

[covert420]

Good point on the VVT engine....

As far as the 275hp vs 300hp goes... I hear the 300hp flat sucks. It is supposedly nothing more then a different cam designed for higher rpm power. It may just be me, but I dont like the idea of having a V8 unless it is for the torque/grunt. High-end power if for turbo-charged I4s. I like the idea of being able to get out of my own way when I need it, not ricer running some guy from 60MPH on the interstate.

I would assume some PCM tuning would be required with any engine swap, but I was under the impression from what I read that the transmission in our cars simply would not work with a 4.6L.

[stevensolds]

the tranny would probably just bolt right up, provided it is the same gear ratios. A 4T80E is a 4T80e.. Also i think our tranny is under-rated about 10 or 20hp. I remember on the caddy forums a guy mentioning he was putting out in excess of 325hp and he drives fast a lot, not any tranny problems. I think he had like 60k miles too

[Aurora40]

It's torque that the tranny can't handle, not power. The 4T80-E is rated to 315lb-ft and I think 6700 rpm.

In theory, then, it could handle 400hp.

[oldsauroraman1]

Jim's line of thinking is more easily adapted. Make the mods on your intake/exhaust/computer. Then see what your HP is at - it will be pretty close to the 275-300 range. :-)