Embarking on the 4.9 swap

[Dylan49]

What's up guys! New to the forum but I've been reading posts from here since I bought my Reatta in 2017. I've always had big plans for it going from wanting to turbo the original 3.8, twin charging a series 1 or 2 3.8, doing the 4.9 swap all the way to swapping in the SBC 283 I'm building and convert to rwd but I've realized that's out of my means at this point in my life... Maybe in the distant future. But I want something. I own both an 89 Reatta and a 92 Eldorado. I have alot of fun driving the Eldo and love that the 4.9 is fairly simple. I also know they share the exact same subframe so mechanically this is a bolt on swap that I should be able to do in my tiny apartment garage on jackstands. That being said, I know I'm going to run into issues with touchscreen and cluster functionality. I've been told that if I use a 1989 Cadillac BCM in place of my 89 Reatta BCM that I may still have control over my radio, climate control, and possibly working gauges. (Which is all I care about) the other touch screen extras are cool but I can live without them as long as I have access to the regular stuff. I know the onboard diagnostics will also not work anymore which is fine with me. I know this swap has been done at least once but it's hard to find any info or even any pictures on the Reatta it was done to. I'm wondering if anyone could help shed some light on this for me?

To conclude this I plan on doing some very mild mods to the 4.9. it already is fun enough to drive for me in the Cadillac, i figure a few hundred less pounds in the Buick would make it even more fun in addition to: Allante Intake swap, ported heads with the intake matched, and a custom exhaust system. I have no desire to go further into the engine than that. And it already has enough power to smoke the tires a bit which is awesome. Again, I know mechanically this swap should be "cake" where I have a bunch of question marks is making it communicate with the Reatta instrumentation, windows, gas cap/trunk and whatever else might communicate through the ecm/BCM. The combo I plan to try to use is a 1990 Eldo 4.5 ecm reflashed for the 4.9 by Sinister, with an 89 eldo BCM. I've included a crappy Photoshop of what my Reatta would look like with the engine in there. I definitely like it 

 

[Dylan49]

I know there is a matter of matching data streams i just don't really know how to go about that, do I need any more equipment than a laptop? Is it possible for me to get the ALDLstuff file and match the bytes on my laptop and then send the actual BCM unit off to sinister to have it flashed to the bytes that I manually reorder in a basic program like Excel or ms word or something? If someone put a Northstar in an 89 you would think a 4.9 would work easier. I know the screen wasn't functioning properly in the Northstar but it was still on and displayed SOMETHING. 

[Barney Eaton]

Keep us informed........ probably not much help here as few swaps like your plan have been documented.  

If you go rear drive,  I would look for a GM vehicle (with 115 bolt pattern) was offered in AWD     That would simplify

the rear suspension as it would be a modular unit. 

[handmedownreatta]

if you swap the senders from the 3800 to the 4900 the guages should still work.might even be the same senders.fiero swap people know all these things.ask on their forum.

 

Edited February 11 by handmedownreatta (see edit history)

[wufibug]

I believe Daniel said he was going to do this swap also.  Way back when the Reatta was in production, a team was created to look into a Turbo version.  The main problem they encountered was the front wheel drive technology was not up to the demands of the engine.  I doubt that the transmission or the transaxle are going to last very long if you intend to drive the 4.9L V8 to its potential.  Years back someone tried to install a beefier transmission and got into a lot of serious cutting and welding.

[handmedownreatta]

20 hours ago, wufibug said:

I believe Daniel said he was going to do this swap also.  Way back when the Reatta was in production, a team was created to look into a Turbo version.  The main problem they encountered was the front wheel drive technology was not up to the demands of the engine.  I doubt that the transmission or the transaxle are going to last very long if you intend to drive the 4.9L V8 to its potential.  Years back someone tried to install a beefier transmission and got into a lot of serious cutting and welding.

i assumed he was using the 4.9 transmission.4.9s are only 200 hp,much less than a sc 3800.ive looked at them for my fiero.

[Barney Eaton]

If staying with front drive,  I believe the 3800 supercharged engine is the best all around upgrade. 

It pretty much drops in place.   Must use the transmission that came with the supercharged engine as it 

was already beefed up to handle the extra power.    

If you are set on going rear drive........then install any thing you want because you will be inventing the wheel 

with whatever combination you use. 

[Kevin M]

I remember a thread from years ago about someone who started on the rear wheel swap. And got halfway through and gave up on the project. I know I’ve seen at least two reattas with north stars in them. So that should be doable just don’t know how they did it. 

[Barney Eaton]

It may seem like we are trying to discourage this person from doing this project.    Maybe it is the way the replies are worded but 

from my standpoint that is not the message..... I am telling them we just don't have details.    I have done lots of things that I did not 

know better when started.   Way back in the early '60's a co worker ask me if I could change the engine in his sons car.  To this day 

I don't remember how I pulled a inline 6 from a '55 chevy and installed a V8... I had no engine hoist or even a large tree.   In addition it 

was all done in the back yard of my parents house with a collection of tools and wrenches that were not even a set. 

If you have a idea or dream.........go for it. 

[handmedownreatta]

i REALLY  HATE it when people like dylan don't answer answers  to his post...

Edited February 25 by handmedownreatta (see edit history)

[Ronnie]

1 hour ago, handmedownreatta said:

i REALLY  HATE it when people like dylan don't answer answers answers to his post...

I hope you don't mind me editing your last post just a little bit. I really hate it when that happens to but I don't hate the  people who do it. 

[Dylan49]

Hey y'all, its been a while. Wanted to let everyone know this is still happening. Sorry for not replying at all I didn't have any email notifications and nobody replied to my post until a few days after so I figured nobody cared or thought I was actually going to go through with it. Anyways, a couple clarifications:

1. I will not be going rwd with the 4.9, I had plans to go rwd with a 283 that I'm building on the side but with my current living and money situation that isn't realistic for me.

2. Currently my Cadillac is my daily driver, I actually use it for my lawn care business but I'm going to be purchasing a very clean daily driver condition El Camino in the next few weeks to become my new daily. Once that happens I'm going to cut my Eldorado in half and make a trailer out of the ass end. And then cut the body off the subframe/powertrain. 

3. I'm definitely going to look into using the 3.8 sensors on the 4.9 to help with my gauges.

4. I'm looking for people with knowledge on the Allante 4.5 and the 4.9, i know I'm going to use the Allante intake but I would like to try and find some info on if the Allante 4.5 has other bolt on upgrades that could be transferred to the 4.9. Are the heads better flowing? Do they have bigger valves? Would it be just as cost effective to have the stock 4.9 heads port matched to the Allante intake? Did the Allante have a different cam profile than the 4.9? Is it possible it's just as simple as the intake + a retune? Like I said before I don't really want to tear too much into the engine because I really would like to have fun and drive it around asap but I would like to try and unlock some potential with factory GM parts. Again, sorry for taking so long to reply! I'm definitely going to do this swap and I hope i can get some knowledge from everyone on things I might not know about. Thanks again everyone! 

[EmTee]

The Cadillac 4.5L used in the '87 - '92 Allante' and the 4.6L (Northstar) used in the '93 Allante' (and later Cadillacs) are totally different engine designs with no parts interchangeability.

[handmedownreatta]

1 hour ago, EmTee said:

The Cadillac 4.5L used in the '87 - '92 Allante' and the 4.6L (Northstar) used in the '93 Allante' (and later Cadillacs) are totally different engine designs with no parts interchangeability.

i see no mention of a 4.6.

[EmTee]

OK, wasn't sure if he meant the 4.5 or possibly Northstar (4.6).  Carry on...

[Dylan49]

So I checked out rockauto to see if the 4.5 and 4.9 heads have different valve sizes and they are the exact same. Now I just need to verify if theres anything different with the intake runner design. I also verified that the stock cams for both engines are very similar if nol so that takes that out of the equation. Really didn't think a tune + intake could generate 20 HP but I guess with stock engines that are designed to be underpowered that's all it would take for GM engineers to make it happen. 

[Dylan49]

To add some more fun to the forum, my exhaust setup for this is going to mimic the newer style civics like this: only I'm going to be using 2 spintech 6000s on the outside and a Porter shorty on the inside. I'm also gonna put a Borla Polyphonic Harmonizer behind all 3 of them. I haven't done much research into aftermarket cats yet if anyone has any recommendations. I'd like to get a set of custom headers done for this as well. I have noticed that the civic has tank conveniently has a slot for the exhaust to fit under where our Buick does not, would I be able to take a hammer to my tank and "make" a slot or would it be better for me to try and find an aftermarket tank?

 

Likely the order of operations for this will go like: 

1. Complete the swap with the base engine as is.

2. Civic style muffler setup 

3.Allante intake/Valvtrain swap

4. Custom Headers/Low Boost turbo (yes I do want to put a 4g63 turbo on my 4.9) 

5. After it likely blows a gasket I would have the heads ported and look into going a size up on the valves if possible. 

Obviously if it was to blow at anytime before step 5 I would do all the machine work then but I want to do this project and drive it as much as possible so I want to be able to drive it stock and then upgrade 1 by 1 and really feel how much each upgrade eventually does. All while enjoying the use of my beloved first car.

 

Edited April 10 by Dylan49 (see edit history)

[Ronnie]

So far what you have posted is commonly called "bench racing". Nothing wrong with it. It seems to be a hobby for a lot of people who visit forums.

[Dylan49]

48 minutes ago, Ronnie said:

So far what you have posted is commonly called "bench racing". Nothing wrong with it. It seems to be a hobby for a lot of people who visit forums.

Right, the only thing I can guarantee that will actually happen is the swap itself. And the 3 mufflers in the rear. And that's short-term happening within the next 6 months. Any headwork will be done way after, and the Allante intake swap requires me to collect all the necessary parts first. Like I said my main priority is to have it drivable asap. The only thing stopping me from starting is the need to a new daily driver. Although I suppose i could start on taking the Buick subframe out... I have a small apartment one car garage that I somehow need to use to cut my Cadillac up and keep the ass end in the very back for when I'm ready to make it a trailer. Keep the 4.9 off to the side, and then get the Buick back in to drop ITS subframe. Going to be a bit of musical chairs. All of this is happening though because I'm trying to plan a move to Arizona within the next 2 years to settle down for good. I just turned 25, ive taken my Reatta and it's 3.8 everywhere from hwy 1 in California to lake superior in Minnesota. It's seen the grand canyon and mt Rushmore. It's my favorite thing in existence i think lol. What needs to happen for me to make the move is: I need to downsize from 3 cars to 2. The plan is to have the Buick 4.9 tow my homemade Cadillac trailer with a bunch of my stuff. And then use the El Camino that im purchasing soon to get the rest of my stuff, maybe tow a small uhaul trailer behind it. I'm from the Bay area in California but ive been living in Dallas the past few years. All I know is that I want to build my Buick and move to Arizona lol hopefully y'all are down with that and can maybe point me in the right direction for a few things!

[handmedownreatta]

Cadillac High Technology engine - Wikipedia

[Dylan49]

25 minutes ago, handmedownreatta said:

Cadillac High Technology engine - Wikipedia

Not a whole lot of info here I didn't know already haha

[handmedownreatta]

15 hours ago, Dylan49 said:

Not a whole lot of info here I didn't know already haha

their main appeal is they are lighter because of the aluminum block.great for fieros but only 35 hp more than the reatta engines.

[2seater]

Bench racing or not, throwing out crazy or impractical ideas provokes thinking and conversation 👍

 

The Reatta fuel tank is a purpose built and probably not worth trying to modify due to its design. A trunk mounted fuel cell would seem most practical. It’s just me, but working out exotic exhaust would seem way down on the list😊 Maybe consider rear mounted turbo’s instead of mufflers? A V8 is easier to muffle than fours and even sixes. Just $.02

[wufibug]

Just a minor correction to EmTee's post.  The first Allante's, the 87s used the Eldo 4.1L V8. As the Eldo motor grew from 4.1 to 4.5 to 4.9 in 1992, the Allantes followed suit.  The Eldos had throttle body injection while the Allantes had tuned port. The engines were the most, if not the only reliable thing in the Allantes.  The electrics are a nightmare.  Ran over a large traffic cone in my 87 Allante.  It got stuck under the right side and did something to the lighting on that side that I have never been able to track down or correct. The onboard diagnostics remind me daily that there is a "lighting fault" but there does not appear to be anyone left on the planet who can diagnose that system including a former Caddy dealer mechanic who gave up on it.

Didn't Shorty do this conversion successfully?

[Dylan49]

1 hour ago, wufibug said:

Just a minor correction to EmTee's post.  The first Allante's, the 87s used the Eldo 4.1L V8. As the Eldo motor grew from 4.1 to 4.5 to 4.9 in 1992, the Allantes followed suit.  The Eldos had throttle body injection while the Allantes had tuned port. The engines were the most, if not the only reliable thing in the Allantes.  The electrics are a nightmare.  Ran over a large traffic cone in my 87 Allante.  It got stuck under the right side and did something to the lighting on that side that I have never been able to track down or correct. The onboard diagnostics remind me daily that there is a "lighting fault" but there does not appear to be anyone left on the planet who can diagnose that system including a former Caddy dealer mechanic who gave up on it.

Didn't Shorty do this conversion successfully?

My 92 Eldo is PFI not TBI, from my understanding the 4.5s started out as TBI and then halfway through their life they got a head upgrade and PFI. The Allante 4.5 is the only one that had the TPFI right?

[Dylan49]

7 hours ago, handmedownreatta said:

their main appeal is they are lighter because of the aluminum block.great for fieros but only 35 hp more than the reatta engines.

Not much more HP but the Torque is great and the V8 sound is also nice, plus I'm gonna love steering the Reatta with that Powe steering boost haha

[Dylan49]

3 hours ago, 2seater said:

Bench racing or not, throwing out crazy or impractical ideas provokes thinking and conversation 👍

 

The Reatta fuel tank is a purpose built and probably not worth trying to modify due to its design. A trunk mounted fuel cell would seem most practical. It’s just me, but working out exotic exhaust would seem way down on the list😊 Maybe consider rear mounted turbo’s instead of mufflers? A V8 is easier to muffle than fours and even sixes. Just $.02

The reason I want to start with the exhaust mufflers once the swap is complete is because I really want to drive the car around asap and that's something that I can still do that with. When I do the Allante intake I'll have to wait for my ECM to be released before I can drive it again

[EmTee]

2 hours ago, wufibug said:

The onboard diagnostics remind me daily that there is a "lighting fault"

Not to hijack the conversation, but do all of the lights still work?

[handmedownreatta]

1 hour ago, Dylan49 said:

Not much more HP but the Torque is great and the V8 sound is also nice, plus I'm gonna love steering the Reatta with that Powe steering boost haha

im in a similar situation.i bought a 92 hp fiero to swap my 160 hp 3800 into but everyone tells me not to.find a 240 hp 3800 supercharged engine instead.

[Ronnie]

5 hours ago, 2seater said:

Bench racing or not, throwing out crazy or impractical ideas provokes thinking and conversation 👍

That's much easier than twisting bolts for sure.

[Dylan49]

5 hours ago, handmedownreatta said:

im in a similar situation.i bought a 92 hp fiero to swap my 160 hp 3800 into but everyone tells me not to.find a 240 hp 3800 supercharged engine instead.

Yeah it's one of the easiest way for the most stock HP but I'm not into doing the easiest most boring swap I like doing out of the box things. What's cool with the 4.9 swap is mechanically it's as easy as it'll get, what's going to be a challenge is engine management and getting everything to communicate with the Buick BCM and cluster/touchscreen 

[Dylan49]

I do think it would be fun to try and build the 4.9 to compete with the Northstar and LS. Obviously I need to gain 100 HP to make that more of a reality and that's much easier said than done. That being said the 4.9 is 300 CID so pushing 300 HP out of it should be attainable. If they pushed out 283 HP back in the early mechanical fuel injected 283 why can't I get 300 hp out of a tpi 300?? I would definitely dub the engine: "The Northstar Killer" the more I think about it the more obsessed I'm becoming lol. I feel like it's my duty to produce a 300 hp boosted 4.9 and destroy one Northstar and one LS in a legit drag race with the Reatta lol

[EmTee]

8 hours ago, Dylan49 said:

I feel like it's my duty to produce a 300 hp boosted 4.9 and destroy one Northstar and one LS in a legit drag race with the Reatta lol

I will say that my wife's '93 Allante' will leave the traffic light with authority if I apply pressure to the go-pedal.  300+ HP out of a 4.9 would seem doable (e.g., supercharger or turbo).  The big problems will be building the transverse transmission to handle the torque and managing traction.  Supposedly there were 'tweaks' made to the 4T80E used in the '93 Allante with the "V4J" mid-year update.  Also, note that the '93 Allante' used a 3.7:1 differential gear ratio, whereas the earlier cars had a 3.2:1 final drive ratio.  So, you'd probably want to find a '93 4T80E from an Allante' or ETC and then have it beefed-up as much as possible.  Even so, the other problem will be getting that power to the pavement with a FWD architecture...

 

Edited April 12 by EmTee (see edit history)

[Dylan49]

40 minutes ago, EmTee said:

Even so, the other problem will be getting that power to the pavement with a FWD architecture...

 

Are you referring to needing different axles to stand up to the extra HP and torque? 

[EmTee]

No, I was just saying that GM updated the 4L80E to handle the Northstar (V4J), so if you're planning to modify a 4.9 for comparable power it would make sense to either find a V4J transaxle, or have the 4.9's transmission rebuilt to V4J specs (or better).  The '93 Allante also had a deeper final drive ratio (3.71) which would help off-the-line performance -- IF you can manage traction at launch.

[Dylan49]

2 hours ago, EmTee said:

No, I was just saying that GM updated the 4L80E to handle the Northstar (V4J), so if you're planning to modify a 4.9 for comparable power it would make sense to either find a V4J transaxle, or have the 4.9's transmission rebuilt to V4J specs (or better).  The '93 Allante also had a deeper final drive ratio (3.71) which would help off-the-line performance -- IF you can manage traction at launch.

Oh my bad I read that wrong at first, thanks for the info on that transmission btw cause I'll definitely start trying to look out for one 

[EmTee]

4 hours ago, Dylan49 said:

I'll definitely start trying to look out for one 

I'm not 100% certain, but I read somewhere that the Eldorado ETC used the same drivetrain as the Allante', so it may also have the 3.71 axle ratio.

[wufibug]

EMTee, the traffic cone was lodged on the right side in space in front of the radiator. It disconnected the power steering cooling hose but that was an easy fix.  After that which the passenger headlight ceased to work and the lighting fault warning became a regular startup feature.

[EmTee]

29 minutes ago, wufibug said:

After that which the passenger headlight ceased to work...

OK, I just wanted to confirm that there actually was a fault and it's not a false alarm.  I'll look at the shop manual and see whether I can find any clues.

[wufibug]

I've got the shop manual for the 87 and looked through it.  t talks about the redundant systems and lighting modules. I was thinking about the "lighting module" but I can't locate it, have no idea what it looks like, or whether replacements are available. I really appreciate the thought you are giving to this. If you have any insights, please feel free to email me.  

Richard