3400 3500 hybrid questions

[TheOtherStyle]

Hi all, looking to get back into the GM scene soon, and have some questions regarding the swap. First, I did look at the stickies, didn't see what I was looking for. Currently working my way forward from the beginning threads in this section, but so far still haven't found all that I'm looking for.

The swap is part of a combo upgrade I'm doing. The vehicle in question is the U-body van, 97-up. Not sure which model because I haven't thrown down for one yet. I know they come with the 3400 and an automatic. Not sure which automatic but it's not relevant as I'm planning on ditching it for a manual. The vans were sold overseas as Vauxhaull/Opel, which were available which a manual, so the firewall bits should be there for the clutch pedal, theoretically making this fairly easy.

Moving on....

I've looked through the WOT webstore, and between that and threads on here, I'm under the impression that the swap is pretty straightforward. 3500 heads, lower intake, and gaskets, 3400 everything else. I'm looking at purchasing the top end swap from WOT, along with the extras like the upgraded throttlebody and the Comp Cams bumpstick.

Questions I have about this (but haven't found on here yet, though I'm still looking), is what kind of numbers should I expect from the motor with the swap done? Does the compression ratio change at all? Second question I bring up because I saw something in one thread regarding a change in compression ratio, but wasn't sure if that happened as a result of this swap. In that regard, what compression ratio could I expect once I'm done?

From what I know of the cars vs the vans, I should be able to get away with headers for any of the cars. Who currently produces headers besides WOT? I notice they are currently out of stock, and my best guess is that since they are something of a niche store, they likely do them in batches every so often. So looking to keep my options open...to anything but Pacesetter.

Also, from what I've seen the 3400 exhaust manifolds bolt up to the 3500 heads (correct me if I'm wrong).

Last question for now is this: What ecu should I look for to be able to use the manual transmission (figuring a Getrag 282 unless a better option comes along)?

That's all my questions for now, I thank everyone in advance for any answers. I'm still looking through threads, working my way forward, and am making notes as I find information, just haven't found all my answers yet.

I understand that since I'm planning this in a van (heavier vehicle), it's not going to be the fastest that I could build, but I'm fine with that. Lately when I wanna go REALLY fast, I throw on my gear, jump on my bike, and rip the throttle until the world goes plaid lol.

[WrathOfSocrus]

Welcome to the site! The 3500 heads have a slightly larger combustion chamber, so the compression ratio does drop a bit. Using the CR calculator on here says it will go from 9.64:1 to 9.12:1. The increased flow and velocity will more than make up for the slight drop in compression.

Horsepower gains are largely dependent on how well the rest of the flow in and out of the engine is addressed. The air from the box to the TB is pretty short and shouldn't need modification. The side of the box where it pulls in air from the fender is much smaller in diameter than the rest of the system and needs to be opened up a little. On the exhaust side, the manifolds will bolt up to the 3500 heads and the vans have the 'header' style rear manifold. The biggest bottleneck there is the flex joint in the downpipe. It measures ~1 3/4" on the inside. If you decide to wait on headers and want to use the stock manifolds I would look into getting a custom downpipe made. If you can get a flange made to bolt up to the rear manifold the opening there is actually something around 2 1/4" - 2 1/2". So a custom pipe 2 1/2" all the way to the cat will let the engine breathe better.

The cam is another aspect to the way the engine breathes. This will be the real determining factor as to your total HP. WOT-Tech can set you up with what you need.

With the computer I think you might be able to tune it to disable transmission related DTC's. I'm not entirely certain how it works but if I remember correctly I saw the HP Tuners has credits for the Montana van but doesn't have the Venture listed. I'm kind of curious about how all of that works if you can use any van and just swap the computer with one that is supported. Or if the pin out is the same between the different van makes and models (short wb and long wb). The front half of the van is identical to the 3400 equipped W body cars; engine trans suspension, maybe the W body computer would also work but I have no idea and would love to find out if anyone here has information on that. Since you will need to tune the computer for the camshaft I doubt it would be too difficult to get the computer to comply without the 4T65E.

Good luck finding a van and let us see pics when you get a build going

[HOYS]

I wish I had money to top swap my mini-van!

As far as headers go...they most likely will have to be custom. I have not looked closely at the exhaust setup on my van but I'm going to go out on a limb and guess that it is different than an N-Body in regards to firewall clearance and down pipe to cat-back geometry is different.

One thing I noticed from your post (it might just be your wording). Make sure you use 3400 head gaskets and not 3500 for the top swap!

Keep us posted!

[TheOtherStyle]

What van do you have? Venture/Montana/Trans Sport/Silhouette? If you have one, is there any chance you snag a series of pictures of the underside, including suspension?


I notice that WOT includes 3500 metal headgaskets, what is the reason for saying 3400 gaskets?

It'll be a bit before I have the van, and subsequently the funds to do the upgrade, but I like planning ahead, learning what I can about modding different motors. Who knows, one of my friends might wanna do some work on his car before I'm building mine, and if I happen to have the info at the ready, guess who gets paid to do the work


Also: Just went through the WOT website to price everything to do a full rebuild at the same time....heheheheh pay to play as they say...

[HOYS]

Silhouette. I have to do some work on it soon so I'll try and snap some pictures.

Hmm... I always thought you were supposed to use 3400 head gaskets. I must be wrong.

[pocket-rocket]

Welcome to the site

As far as the underside to the vans, I don't have one, but like WoS mentioned, they are set up like a W body. From what I remember from working on a 99 Pontiac TranSport, the rack is mounted to the subframe and the downpipe goes up and over, so you should probably get W body headers. I would wait for pics from someone though, or when you get a van.

[Daguse5853Z]

does jon 3x00-modified post on here alot? Im pretty sure the 97 pcm upgrade is a minivan pcm among others compatibles...I think my pcm is from a 97 pontiac but its been so long. I say stick to the early minivans for ease of tuning. Find a well kept early example and build on it. The last year transports had 3400's btw...the ones with the weird bug eyes. Its a little known fact I'm surprised I dont read alot more about. They might be obd2 as well since they're 96 model year but fugly snd I never had a example to plug into (jy versions dont have batts or keys to test). DHP is pretty forgiving with the model specific crap but my version is as old as the hills so maybe that changed....

[pocket-rocket]

does jon 3x00-modified post on here alot?

Yes, he do

Well, not so much here lately, but traffic across the site has been slow lately.

[walterdude]

Jon lives about 20 miles from me and we got SLAMMED with Irene!! Declared a disaster area!!! According to some early reports his area was going to be without power untill Wed, yesterday!! I just got my power restored on Mon after 8-9 days.... Maybe that's why he hasn't been around??? If I recall he works in fibre optics or something like that.... Maybe FLOODED with OverTime??
Just a thought,,,,,
Tom....

[3400-95-Modified]

Shit, Tom... Where do you live that I have never bumped into you? LOL

Yes we got power back last wednesday, exactly 5.5hrs after I bought a generator.... LOL It was 4 days without power at my place... My parents werent till Friday IIRC and a friend just over in Moosup didn't get power back till Saturday afternoon. We just got hit again with the last band of rain from the other storm and had quite a bit of flooding around here agian... Nothing major in my area thank god.

Now about the PCM swaps... a 97 venture PCM works in a 96 Beretta to gain a few more tables and better OBDII controls. But this sounds like he is already starting with a minivan to begin with. If he's curious on tuning support, you can probably flash it with the same 97 Venture Bin I'm using and thats supported by DHP. If you have a HP Tuner you can probably get away with using a 97 Monte Carlo Bin, but you would have to copy over most of the trans tables from the 97 venture if you can get them from someone in xls form... since I'm not sure if the Monte came with a 4t65e like the Venture did.