3800 engine swap

[jason1973tl]

Hey guys,

Run accross an add for a gm 3800 v6 engine and transmition for 995 dollars. How hard would it be to swap out the 3400 for the 3800.

Hope to find someone with a little more expertise than myself. Would it be worth the swap, I know for a fact the 3800 is a much superior motor than the 3400.

Thx,

Jason

[1999montana]

Jason,

Can't say that I know the answer, but what I would do is get the two engine transaxle assemblies next to each other and start taking measurements (ie distance between the engine mounts - and number of mount postions, some engines have three or four mounting points, width and length of the engine and then take some measurements of the engine bay too.

The best place to do this would be at a wrecking yard if they'll let you wander around. A van chassis that has been stripped is idea for engine room measurements. However, these days most of the yards around our area want to know what you are looking for before they'll even let you go in the yard.

Might be quite an adventure though, and then at least you'll know if it will fit. Then you have to figure out if everything will connect: - cooling rad hoses, fuel and trans lines, engine electrical, cables for trans and throttle and a huge nest of vacuum lines and such that would have to be figured out.

Being an old hot rodder I found the best way to do this comparison was by putting two shop manuals side by side (in your case a Buick with a 3800 for instance and the Van) and comparing the differences between the two power trains.

Questions that come to mind: will the axle shafts mate to the 3800 transaxle and if not, will the 3800 axles fit the van?

See what I mean? It's probably a lot of work, but I'll bet someone has considered it or already done it!

As Kodak would say, "Let's see what develops".....

[cdru]

For a Montana, you are probably looking at nearly impossible to impossible. The engines are different physically, requiring different transmissions. In addition to a new transmission, you are going to need different wiring, computer, etc all that was never ment to be in that van.

I won't say it can't be done, but to me it wouldn't be worth it.

[Jack Bobaganoosh]

Hi there all, I am a new guy and found this place looking for info on changing the LIM gapsket.

I am starting to look at a 3800 engine swap (I have a 97 Riviera with the S/C'd L67 3800), and the only thing that I can see being a major obsticle is that the 3400 is a 60 degree motor, whereas the 3800 is a 90 degree, hence, it will be much wider. Granted, a 5lb sledge and a torch go a long way, but that would be the major hurdle. The trannies are the same (N/A 3800 and the 3400 both use the 4T65-E, the L67 uses the 4T65-E HD, which uses a higher 2.93 gear ratio).

[cdru]

I still don't think it's going to fit. But hey, if you want to try, knock yourself out. Don't forget that in order to do anything in the back of the engine, you probably will have to remove it. There is barely enough room to rock the engine forward with the 3400...spreading the cylinders an additional 30 degrees as well as a physically larger engine isn't going to give you more room to rock it.

[Jack Bobaganoosh]

That is why my second route would be looking into the new 3.9L motor, which shouldn't be that much wider than the 3.4. Plus, my in-laws own an auto shop with lifts, so getting the motor/tranny out won't be a problem.

[MagnaPilot]

I'd say there is a good chance it could be done. Considering the Lumina/Trans Port version of the van is largely the same as the Montana/Venture family and they had the 3.8L in it. The fenders may be wider or smaller or the nose could be shorter though. Some articles I've read say that they are nearly exactly the same chassis wise. So it may very well nearly bolt right in with the older 3.8L mounts. The S/C may be of hinderance considering it's added size. I haven't seen one up close so I don't know how much bigger it is. From what I've read, the cradle/front subframe of the Montana/Venture is the same that is used in the Impala W-Car family, down the to the exact brakes and all. Let me know what you find out, I'd like to know myself.

[GivenGift]

I know this is old but it still comes up as #3 in a google search so I figured I'd help it update. [IMG][/IMG]
Very easy and cheap swap guys! The engine and trans is a bolt in and even the stock 3400 dog bones line up as long as you stick to grand prix mounts and accessories. I highly urge you to source a GTP or other W Body engine for the swap as you'll need the steel oil pan and accessory drive from a W Body car. You will be on your own for a harness and I suggest the best way is to take apart the 3400 harness and "blend" it with the W Body harness. If you have a short box van with no rear A/C I think the GTP ac lines are also a bolt on to Van's the receiver dryer. I have my rear air working but I had to do surgery on the lines. If you decide to use the 4T65 HD trans you will need to take the passenger side non HD inner CV joint apart and use an inner joint for the HD trans. You will also have to weld a throttle bracket using the 3400 bracket and the 3800 bracket. Not really a big deal at all. You'll need to make the little things like fuel lines and radiator hoses but I think a stock GTP lower hose worked fine. I also used a GTP power steering hose. From an "engineering" stand point the 90 degree V6 might not crash as well and tuck under properly in a frontal crash but since these vans crash poorly anyway I guess that little detail make no difference!

Servicing the van is actually easier with the 3800. Plugs are doable as installed with #2 fairly hard but not nearly as hard as an LT1 F Body! I had to swap idler pulleys and that was also no issue. Alternator is easy. The O2 sensor is a bit tough to replace but if you use a crow's foot O2 socket you can do it. Anything is easy to work on compared to a V8 Taurus SHO! No maintenance issues except for adding PS fluid as there is no divorced reservoir like the Series 1 C/H cars had. That could be added if need be.

My van has a stock 3800 with 2.93's that Ed Morad cut me a good deal on. I tossed a 3.4 on her and did my own DHP PCM. My best 1/4 mile ET @ 4,100 pound race weight is 15.05 @ 92. Not fast but consider the mod level and the fact that it was nearly stone stock! Going to the 2.93's from 3.29's before has kept the MPG practically the SAME as before. With my best MPG around 25 on a freeway trip. I swapped the van 3 years ago and it is the best thing I ever did for the Montana. It will HAZE the tires if you feel like punishing the differential! In my 1999, Pass Key 3, Traction control and cruise all work fine. If you are doing a newer van with a Class 2 dash you will need to probably start with a Monte Carlo SS PCM or something that has Class 2 messaging in the PCM OS.

I think what's nice is that you will be hard pressed to tell that GM didn't install this engine from the factory - something they SHOULD have done! Really stupid to have that underpowered 3400 tossing intake gaskets and cam bearings in Mom's family hauler. No wonder they don't build the vans any longer and are sucking stimulus cash.

When the swap is completed there are no NVH issues and the power transforms the van into something very nice to drive that will freak the hell out of people who think you are easy pickings for lane merges and tailgating. Other than an expensive Honda or Toyota minivan with a 250-270 hp V6 where are you going to find a fast or more reliable engine to take the family on trips in?

There are few other guys that have done the swap and Kevin Margitta mentioned that somebody on Toronto has a non intercooled Cartuning kit on one that is running 13.00's!!

I might let mine go for the right price! The rockers are really rusty but all of the parts are there!