bullet_101 Posted January 7, 2012 Report Share Posted January 7, 2012 (edited) First I'd like to say Hi, this is my first post on these forums. I've been lurking for a few weeks but I have a few questions that I haven't found answers too. I recently bought a 91 Grand prix from my boss for 400$. Pretty cheap ride but I want to fix it up a bit and keep it so I have a "winter" car. 1. 3100->3400 swap, what am I looking at to get this done. I know the 3100 and the 3400 are pretty much identical, but in terms of bolting it in and wireing harnesses/fuel rail etc. Should I just grab any old 3400 or are there particular versions that are better than others. Will all versions of the 3400 bolt in and use the 3100 wireing harnesses 2. If the 3400 can be bolted in, and plug and play all the wiring harnesses, is there anything I should do to the engine other than the standard change the lower intake gasket and all other external seals. Upgrades I suppose would follow under this 3. Is there any point in upgrading the rear monoleaf to a different leaf from a different w body. I noticed the cutlass (supreme I think) has a steal leaf. Or should I just get some helpers from moog and deal with it. Thanks for any help in advance Edited January 7, 2012 by bullet_101 Oh god I thought I was posting in power train, could someone move this please. Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted January 7, 2012 Report Share Posted January 7, 2012 The 91GP you have has a 3.1MPFI not a 3100SFI, unless that swap was already done...? The 3400 will bolt up. Youll need to use injectors from your 3.1MPFI (unless tuned for bigger injectors), fuel rails from the 3400. Youll want a 2002+ 3400, as those where the best. Custom tuning will be required to get the maximum performace out of it, or else your running a 3400 on your 3.1MPFI stock tune. Id replace headgaskets and up. If you do the swap, youll need the metal fel-pro LIM gaskets. Theres more to it, but thats a quick version. Quote Link to comment Share on other sites More sharing options...
oldsfever Posted January 7, 2012 Report Share Posted January 7, 2012 I wanted to downgrade to a 3100 from a 3400 when the engine blew in my Cutlass. I was told the wiring harness would be a nightmare so I stayed away from it. I'm by no means an expert but it might be something you would want to double check. Quote Link to comment Share on other sites More sharing options...
skitchin Posted January 7, 2012 Report Share Posted January 7, 2012 I briefly looked at this swap, but the power gains from a 3100 SFI to 3400 SFI just don't justify it. Seems it'd be more worthwhile to get some things ported and use the throttlebody from a 3400(or something even bigger). If you do in fact have a 3.1 MPFI I haven't a clue what applies. But here's some useful info for 3100 http://wot-tech.com/shop/articles/choosing-3100/3400-manifolds/cat_64.html Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted January 7, 2012 Report Share Posted January 7, 2012 Quote Link to comment Share on other sites More sharing options...
rtyarks Posted January 15, 2013 Report Share Posted January 15, 2013 Have made this swap completed it yesterday car runs fine just replace the sensors from the 3.1.MFI to the 3400 block may require you to splice 4 wires two for the temp sensor and the knock sensor Quote Link to comment Share on other sites More sharing options...
j_mezz Posted January 15, 2013 Report Share Posted January 15, 2013 Welcome to the site - are you thinking of an entire engine swap or just the top end swap? I won't have any answers for you on that but in reading your post I wasn't completely clear. As for the rear suspension, I've been looking into this matter myself recently. Everything on my car related to rear suspension and brakes is rusted beyond recognition (but somehow the body is totally solid!). These two writeups have been Very helpful to me as I've been feeling my way through what my next steps should be... converting to rear coilovers: http://www.w-body.com/showthread.php/37622-Coilovers-Adj-Mounts-Solid-Cradle-Bushings-UPDATE-3-25-Design-Done%21%21%21%21?p=651227&viewfull=1#post651227 and swapping in aluminum knuckles and bigger brakes: http://www.w-body.com/showthread.php/46209-Bob-and-Rob-s-Gen-2-Aluminum-Rear-Knuckle-and-Brake-Upgrade-How-To-with-Pics Quote Link to comment Share on other sites More sharing options...
5thgenmonte Posted October 14, 2017 Report Share Posted October 14, 2017 I have a 1999 monte carlo that has the 3100 in it , cam busted in half, I have a 3400 that I'm wanting to drop in but can't find a step by step on how to do it I know most is a direct drop in but I want as little as frustration as possible so to EVERYONE ALL IMPUTS ARE WELCOME AND HIGHLY APPRECIATED SO LET THE ADVICE ROLL IN I'M ALL EARS Quote Link to comment Share on other sites More sharing options...
Grandprix1 Posted October 14, 2017 Report Share Posted October 14, 2017 I have a 1999 monte carlo that has the 3100 in it , cam busted in half, I have a 3400 that I'm wanting to drop in but can't find a step by step on how to do it I know most is a direct drop in but I want as little as frustration as possible so to EVERYONE ALL IMPUTS ARE WELCOME AND HIGHLY APPRECIATED SO LET THE ADVICE ROLL IN I'M ALL EARSCan I ask how your cam broke in half? Quote Link to comment Share on other sites More sharing options...
5thgenmonte Posted October 15, 2017 Report Share Posted October 15, 2017 Ha you know k wonder the same thing! Honestly I'm not to sure as to how it happens one day was driving fine, started to idle a little odd so I stoped and got some plugs, oil+filter, pvc, air filter and such went home put air filter, pvc, and plugs in took it for a small drive ran wonderful, took the girlfriend out for dinner on the way threw a misfire code (found out by stopping at autozone for code scan) so I bought new plugs and wires went back home swapped new parts ran fine again next day tried going out to eat again and it started ticking on the way home pulled to the side road went under hood checked everything decided I'm going to try and turtle it home (about 30 min away) almost reaching my home car started loosing power slowly speed was dropping lights dimming everything no loud noises or anything coming from the engine it just died. Quote Link to comment Share on other sites More sharing options...
5thgenmonte Posted October 15, 2017 Report Share Posted October 15, 2017 Next day towed it home started ripping it apart to see what was going on, took both intakes off seen there was shreaded cam bearing in the valley under the intake got to looking decided to turn engine over by hand, seen the from half of the valves,lifers and cam moving. So my guess is it sound a cam bearing that got caught somewhere chewed it up as well as flattened one side of the roller of 2 liters, when I took the uim off a runner and cylinder was full with fuel, so maybe an inj. O ring popped? When I removed all the injector at least 4 of looked as of there where about to go and one was not even an o anymore it split so it split in half. So I'm not to sure what caused it. Hated the engine but I love the car Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 15, 2017 Report Share Posted October 15, 2017 3800 swap Quote Link to comment Share on other sites More sharing options...
5thgenmonte Posted October 15, 2017 Report Share Posted October 15, 2017 I wanted to do a 3800 swap and looked into it for a long time but I need to get this car going and stay within my budget and to do that requires me to be at a 3400 and I have a 3400 I just need any and every bit of advice possible to do the swap I know a lot of it is plug-and-play but I also want to know the specifics like can I use the flywheel from either or engine or are the motor mounts on the bottom the same do I have to alter anything or change anything to put the engine in the car I tried to start my own Thread about this but I can't figure out how to do it Quote Link to comment Share on other sites More sharing options...
Grandprix1 Posted October 15, 2017 Report Share Posted October 15, 2017 I wanted to do a 3800 swap and looked into it for a long time but I need to get this car going and stay within my budget and to do that requires me to be at a 3400 and I have a 3400 I just need any and every bit of advice possible to do the swap I know a lot of it is plug-and-play but I also want to know the specifics like can I use the flywheel from either or engine or are the motor mounts on the bottom the same do I have to alter anything or change anything to put the engine in the car I tried to start my own Thread about this but I can't figure out how to do it You could get a 3800 out of a junkyard for $300-400. A lot of times you can find them for sale on the Facebook sites pretty cheap. 3800 is gonna be a better bang for the buck in the long run and if you get an L67 theres endless amounts of knowledge and support for them. That being said im sure there is someone on here thats done a 3400 swap... Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted October 15, 2017 Report Share Posted October 15, 2017 I wanted to do a 3800 swap and looked into it for a long time but I need to get this car going and stay within my budget and to do that requires me to be at a 3400 and I have a 3400 I just need any and every bit of advice possible to do the swap I know a lot of it is plug-and-play but I also want to know the specifics like can I use the flywheel from either or engine or are the motor mounts on the bottom the same do I have to alter anything or change anything to put the engine in the car I tried to start my own Thread about this but I can't figure out how to do it If you use your resources correctly, you can get a 3800 for the same price as the 3400. The smart thing would be to look for an S3 and then get an S2 UIM to make it all work. Anyways, the flywheel between the engines are the same. Both used the same 4T65-E trans. The motor mounts should be the same as well. My understanding is that the blocks are the same but the internals are what differentiate them from a 3.1 liter and a 3.4 liter. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted October 16, 2017 Report Share Posted October 16, 2017 An L67 would be a bit trickier but an L36 would be insanely easy. Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted October 19, 2017 Report Share Posted October 19, 2017 An L67 would be a bit trickier but an L36 would be insanely easy. I meant it as L26 over L36. Quote Link to comment Share on other sites More sharing options...
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