New Guy Needs Engine Swap Help: Bonneville to Grand Prix?

[Mombatoo]

1999 Grand Prix GT, 3800 Series II NON-Supercharged is done. I have found a 1999 Bonneville engine that seems seems correct. It appears on the "interchange" list, however, it looks like the motor mounts don't match up? Will this engine work?
(BTW, I am not a mechanic, but I do some simple things on my own. I have someone to put the engine in for me in this case.)

Thanks for any and all help.

Mike.

 

[l67ss]

You will need following parts from old engine- lower engine mount and bracket, coil bracket, d side db bracket, oil filter adapter, and dipstick tube. I recently completed a park av to 97 monte l67 swap

 

[chatbreaker]

I just did this exact same swap a few weeks ago on my 98 GP, the engine was from a 96 bonneville, so I can answer this pretty well.

You will need to swap out the front engine mount bracket, the rear exhaust manifold, the ignition coil bracket (there's also a stud that needs to be removed CAREFULLY with an e-style [inverted torx] socket from your old engine, and there's probably a pan head torx bolt on the new engine, below the front cylinder head by the water pump, this is a bracket for the ignition/motor mount).

Coolant hose connectors for the heater hoses should be swapped out, the ones on my engine were 90 degree bends from the bonneville, and straight out from the GP engine. Those aren't a parts-store part, so be careful - also, replace the rubber o-rings when you get them out - they are secured with 8mm bolts.

AC pump brackets will need to be swapped out as well, there's (I believe) 18mm and 15mm bolts holding it in - these are a PITA, even my impact had trouble removing them.

While the engine is out, it's a good time to replace the valve cover gaskets as well, and take a look at the rocker arms and valve springs - replace or tighten any parts as necessary.

I really wish I had documented the process a bit better, I could do an entire 5 page write up on this engine swap. I also wish I had taken more pictures, so I could have something to share with you as well.

Unsure on the 99 model year bonneville, but on the 96 bonneville I had to swap out the O2 sensor (I just left it in when I swapped the exhaust manifold). The knock sensors might also be different, but they're a self-grounding sensor with one wire, so if you have the connectors that came with them, you can just splice the wires together and bypass the plug.

Also, the oil filter adapter neck needs to be swapped out, since the one from the bonneville engine will hit the passenger side CV axle if left in there.

The O2 sensor bracket will need to be swapped as well, that will come out with the exhaust manifold.

The (vacuum modulator?) on the front side of the intake (right above cylinder number 3, by the fuel rail) will need to be swapped as well, since it didn't come on the bonneville motor in that same location.

Also, the alternator bracket type thing on the rear of the engine between the intake and valve cover will need to be swapped out, that's the long black metal rod looking thing.

Keep in mind, everything on a vehicle is put there for a specific reason, so if something looks different between the two engines, it should probably be swapped.

In my particular engine swap, the junkyard was rather careless about removing the engine, and EVERY SENSOR was broken, so I had to swap out more parts than I would have cared to, but it ended up working out in my favor because I made some intake manifold/EGR changes and I know I have good, working sensors and fuel injectors on my new engine.

Good luck with your swap, if you need any help, feel free to PM me and I'll see what I can remember. I probably forgot a thing or two in this post, if I remember anything else I will definitely let you know. I just swapped my engine within the last two weeks (end of March, 2014) so it's still fairly fresh in my mind.

 

[Mombatoo]

Thanks for the replies: However, I ran across a 2000 grand prix engine that is a direct swap. This is my first time taking on a project like this, though I will only be helping a guy who's done several. I look forward to the learning process, and it's good to know you guys are here!

Thanks again, Mike.

 

[l67ss]

Why not go ahead and l67 swap?

 

[BillBoost37]

Add flex plate to the swap list. Bonneville IIRC always wears a 258mm flexeroni

 

[chatbreaker]

good catch bill, my donor engine came without a flexplate so I had to swap mine anyways. pity I didn't mark the torque converter before I took it apart, I hadn't planned on reusing the stock one. Also, the bolts are supposed to be TTY for the flexplate, but I reused them... hope it doesn't cause trouble down the road ^_^.


As far as the engine swap itself goes, I had my engine out in just under 4 hours, and it was my first time pulling a FWD engine. Just make sure you take TONS OF PICTURES.

Also, this is important:
as you remove bolts, put them in a ziplock bag and label it with a sharpie. for example, dogbone bolts in one bag, alternator bolts in another, ac pump bolts in another, etc. This will prevent losing/mixing up bolts.

The pictures mentioned above will help you remember which bolts go where - long bolts, short bolts, and inbetween. I didn't take enough pictures and probably spent more time removing and switching out bolts than I did actually putting the engine back in the car.

One last thing - don't forget about the ***** bolt. There's probably a dozen threads on how to remove it, but I'll give you a quick summary:

Remove the trans-to-engine bracket on the passenger side. there are four 13mm or 15mm bolts, I think they're 15mm. two go into the trans, and two go into the engine. They're hard to see, so you might have to go by feel. Also, removing the oil filter adapter neck makes it easier to remove the trans bracket - you should probably only remove the one from the old engine, as it's kind of a pain to scrape the gasket off - however, as I recall, the adapter might have to be removed to install the new engine since it will rub on the passenger side strut tower and pinch the engine in the engine bay. There's four bolts holding that on, all 4 are 10mm I believe.

Once the oil filter adapter and the trans bracket is off, you'll need about 40 inches of extensions and an 18mm socket. Getting the socket onto the bolt is pretty easy, but a second set of hands definitely helps. go in from the passenger side wheel well, it's pretty much a straight shot across. Remove that bolt, and as per tradition, throw it as hard as you can into a nearby field. Then, buy a new ***** bolt. ^_^ have fun and good luck!


Oh, and something I remembered after writing all of this: If you have to reuse the flexplate, spraypaint a line between the flexplate and torque converter to align it when reinstalling. On many vehicles, the flexplate only fits the torque converter one way, and it saves you the trouble of trying to line it up 3 different times before you can get all 3 bolts in. On the 3.8L and 4t65e however, the torque converter will bolt up 3 different ways, but supposedly the flexplate is balanced to the TC. For that reason, you should mark it so it installs in the same orientation as it was removed. Not always necessary, but it's good practice.