I want to put an LS1/t56 in my 91 RS to replace the 305 \tbi. My plan is to buy a pullout engine and trans together with the ECM and fuel injection still on it. I want to get a list together of all the extras I need for the swap so I can get a price estimate. I've seen reference to motor mount adaptors, k-members, and fuel pressure regulators, but every list I see is different. What do I absolutely have to change/ modify? I want to keep the A/C. Thanks.

I think what you really need to do is research this. The most important thing is to read about it. Its not the most direct swap and will require you to do quite a bit of work. A good list to start with is here

https://www.thirdgen.org/forums/ltx-...-new-85-a.html

Do some more research at www.ls1tech.com

Use the seach, I'm in the process of doing my swap right now and I've found tons of info that has helped me out, some of the main things are, for A/C you will either have to notch the frame or get a aftermarket K-member for the 4th gen A/C or buy an 3rd gen A/C adapter plate to use the 3rd gen A/C. I myself ain't running A/C......that's what they made T-tops for. Another thing I'm doing is using the 4th gen fuel tank from a 99-up and plumbing my own fuel lines so I don't need a fuel reg. the sending unit has it's own built in, the motor mounts and crossmember mounts you can buy from Hawks as well as the headers and ORY pipe (check out the Hawks ORY thread on here for more info on that), check out LT1 wiring, they have an LS1 wiring service with ECU tuning for dirt cheap going right now on Ebay ($300). The rest is all little stuff, i.e any misc. fitting that you find you will need, hoses, etc. Just take you time and like I said the seach is you friend.

Just for referance I've priced my project out to around $6000 complete give or take $100 or so.

6000? WOW I have under 4500 in mine and thats with buying a tuning program that costs over 500.00 (efi live flashscan-commercial) and all the stuff I payed too much for and the stuff that well... I made some costly mistakes that bumped the cost up a bit.

runs and drives fine. just need to finish up the a/c and cruise which will just push me over 4500 may be 4600 all said and done.

You don't have to buy the expensive headers/y etc or the fancy fuel setup with braided hose, no a/c, no bling items and its certainly doable for under 5k. Its easy to get carried away though, and blow your budget fast. Best way to go would be to find a wrecked 98+ F-body with salvagable engine/trans/ecm/harness/tank/brakes? + anything else you want, swap those items to your thirdgen, then part out everything thats left.

Everything i have to say about it is here;

https://www.thirdgen.org/forums/ltx-...-t56-swap.html

get the 4th gen f-body rad and fans as well

You can use the old rad and fans over, just get new rad tubes, part #'s are floating around in these forums.

Is this is a direct bolt-in and do they cool better than the stock one? The B4C overheats if you look at it wrong...but there are probly more underlying issues

No and no. Use your stock third gen rad. Search it out bro lots of your questions are already covered in great detail

no its not a direct bolt in.
the radiator cap will look all cockeyed
and they're smaller, thinner radiators..


and to top it off, the single RS fan flows more air then their dual fan setup.





however, ignorance is always out there, and one of them is "its newer and it comes with the car, so it must be better"





FYI, the SLP "heavy duty" cooling radiator is actually a LT1 radiator, modded to fit the LS1... this is because the LT1 used the same thicker core as the 3rdgen.

and the 3rdgen radiator is overall larger then the LT1 radiator, and it fits.



so you tell me, what makes more sense? hacking a 4thgen one in, or adapting your 3/4 return line fitting to the LS1s 1/4" and leaving everything else stock?

Good to know, thanks

heres the bare bones of what you need:


mounts.
crossmember.

fuel regulator and line to the stock fuel rail.

solder, soldering GUN, heatshrink.

2 relays, and a fuseblock.

4thgen power steering hose

AC hoses if keeping AC

radiator hoses

barb for radiator, and 1/4" hose for head bleed ports

Alternator/battery/starter cable.. i used a modified 4thgen one.

Y pipe made to fit the factory manifolds.

ODBII connector...


and last but not least.. a flashed PCM or the software to flash it yourself.




do all that, and it runs and drives. everything else is extras.

I used my stock rad. and my stock dual fans. no need to throw money out.

I used the 3/4" nipple on the rad. (I made a 3/4" adapter to 1/4" adpater out of stock brass.) this way the bleed hose went right to the rad. like the 4th gens do

some people just drill the top of the water pump and run the hose there.

the swap was very simple. once you get the motor mounted everything from the 4th gen seems to fit perfectly. a few things are a little close but things like the p/s hose screws right in. coil on the pass side had to be installed last but still fit with room to spare.

Dunno, does this look hacked in? All I had to do was drill the one mounting hole through the lower radiator support, then cut off a 4th gen upper mount, used the existing bolt holes.

There's even a 4th gen a/c condensor stuffed in there as well.

do you really want me to be dead honest about it?


yes.

the radiator cap is cocked at a funky angle.
the radiator itself is too small for the width of the support
the radiator cover/support, while OEMish, looks like crap, and while i know its because i know what my camaro(s) stock one looked like, the stock one looks SOOO much cleaner and better.


btw, why do you have a AC condensor in there when the AC isnt hooked up?






in anycase, im not trying to knock anyone that already did it that way.. im just saying thats far from the ideal way to do it in a thirdgen swap.

From what I've been able to gather, it looks like it'll run about $2k above and beyond the cost of the LS1/T56 for my car. If you add the "wish list" to that, it's about $6700. And that doesn't include PCM tuning hardware/software (of which I currently have none).

But, oh, am I looking forward to it.

Well what is said above may be true, but the the inlet of the water pump would be above the water line in the rad so we dicided to run an ls1 which put's it in the water with the factory ls1 hoses and didn't have to deal with the 3/4 retun hose stuff. We are running the factory duel fans and havn't had a problem with overheating, but we did have to space the driver fan out some to clear. So we are swiching over to the ls1 fans to run the wonder bar since spacing the fans out interfears. The ls1 cooling is so much better then a gen 1, you can run a smaller rad. Infact the ls1 first had revers cooling like the lt1 but it cooled to well. So gm put it back to standard, block them heads. Thats why if you look at the block there are 4 holes like the lt1. So know what other's have done and why before making jugement (ignorant)

this is all your opinion. ours looks stock (factory) for the most part,, but thats how we want it and any pics of our car has the a/c system since we are still working on geting that running, and it will all look like it came from the factory this way. So dont knock others for what there doing we dont all want drag cars. lets see pic of your ride

Actually according to GM, the LSx have standard cooling due to the lawsuit filed against them by the inventor of the reverse flow cooling system...


Anyway, continue, didn't mean to thread hijack.

I got that info from a very reliable sorce, but even if the guy that invented it didn't ok it. If he worked for gm at the time they would own it. So what ever the truth is it has standerd cooling

Socal let me see if I get this straight...

Your advising the O.P. to take out the stock third gen rad which is bigger and cools better and fits perfectly to add more work to his swap by installing a smaller rad that doesn't fit without modifications and then suffer with less cooling capacity and poor fit and finish?

Why?

One reason, it keeps the radiator hoses in line with the water pump, which keeps it as designed by GM in the 4th gens. The lower hose isn't at the bottom of the radiator, but in the middle, like the upper hose is as well. And as for the radiator cap being all jacked at a wierd angle, mine is straight up like it is in the 4th gens as well.

Whatever their reasoning behind that was I can tell you this... My swap NEVER leaves thermostat temps ever. I've been idling away with all the accessories cranked in high 90 degree heat and it still sits happily at 160.

As for the hose inlet location? Rad designs are meant to have the hot enter the top and the cool leave from below. If the hoses are in different locations I bet its baffled inside the tanks to route the coolant to the top and bottom respectively anyways. Can anyone confirm that?

first cam you have a pretty clean swap
Not all rad are hot on top cold on bottom the f-body is a cross frow, and theres not bafillin the tanks. My jeep in a top to bottom flow. You are lucky to not have a problem but we just converted to prevent a problem and haven't had one yet. In fact it made a little more clearance for the intake to clear. We are only putting out the 400hp the gto ls2 produces but heads cam and a blower are ont the way. So when it produces more heat, from more power, if we need to well deal with it then we will.

Are the fans running when it's sitting at 160? My LT1 with the 4th gen radiator/fans sits at 190 idling all day long, I take it down the track, it's sitting on 190, idling back to the pits, 190. My fans are set to turn on at 195 and it keeps it cool. If I had a 160 t-stat in the car, it would run 160 if I had the fans set to turn on at 160.

I have it tuned to fan on at 165 but they dont run very often. I amazed at how cool this thing runs. I have milled heads too. The tune is key my tuner rocks! His 02 centri supercharged/meth Z06 ran a 9.60 last Saturday and hes still sorting it out. Anyways sorry to the OP we're waaaaay off topic here

Apparently swapping out an original 3rd gen single fan is not a "need". I was about to plunk down another $75 for the 4th gen fans.

I guess it's not a "need" but I wanted to keep as much as the 4th gen drivetrain as possible to ensure I didn't have any problems, which even included using the underhood fuse box. My fans turn on and off by the PCM just like in the 4th gen, it will also control the cruise control, and a/c just like in a 4th gen.

That's along the lines of what I was thinking.

Getting cruise to operate was the next question. Again not a "need", but sure is nice to have.

My PCM controls A/C, fans, etc. I didnt bother with cruise I dont really use it. Basically everything on an LS1 gets switched through the PCM via sensors. Rather than on third gens factory that used to sensors to switch the relays. All you have to do is wire the stock relays to the LS1 PCM on the swap. Then you can literally tune in any combination of events you like to control the accessories how you wish. Only one that tricked me up was the fan relay switches negative on my car from factory and the LS1 PCM switches it positive so a few minutes of head scratching and switched a couple of wires around and all was happy happy

you are right but it is just too simple not to say.... the sides are tanks. no other way this is what they are called for that reason. so you don't need to be concerned with the lower hose going to the very bottom of the tank like the thirdgens or part way up like the 4th gens. the tanks are filled and the water pump forces the flow of your coolant through the radiator. from inlet side to outlet side.

ok, theres alot wrong with this.
first, the inlet to the waterpump (and outlet of the radiator) on BOTH is on the lower passenger side... however, its truly irrlevent, as almost anywhere on that tank would work.

i wont argue the reverse cooling thing you stated, since its off topic, but to put it bluntly, you have been mislead.


i agree completly. it is just my opinion.. i also prefer a clean, factory look... my style tends to be a combination of "did that come factory??" and "theres not enough stuff there for that to work..." (aka hidden, 'clean' + 'smooth' looking)
thats just my personal style, and if that was my car, everytime i popped the hood, it would bug me.
its not a attack or anything.
btw, if you can get the search to work for my name (i sure as hell cant) you should find a good bit of pics.
hoses in line with the waterpump??? im not sure exactly what you mean...

in anycase, im running a stock Fbody (non powersteering cooler) upper hose, and a wonderful lower hose.... the number escapes my memory at the moment.. but its spring loaded and fits PERFECTLY in the chassis.. doesnt interfer with the idler arm or anything. i should lookup that partnumber again.. i know five7kid will need it.

EXACTLY.
there is no good reason why. there really isnt.


theres no baffling or anything dude, its just plastic endtanks crimped on a core.. its a simple crossflow radiator.

nope. its not...
if i can stay cool here in summer traffic, you'll be fine.. lol. just swap the fan relay control over to the PCM and dont worry about it...


no offense to you personally, but i hate that train of thought.
i can understand wanting to use OEM componants to remain reliable, and easily source replacement, but i firmly believe you need to do whats right for the car as a whole... mucking in silly things like the 4thgen fusebox, radiator, PCM underhood, etc... things that dont fit and are not required to work right reliably... is just silly.
it may take a firmer understanding of how everything works, but i believe that part of doing it right, is looking at it objectively... not just doing it that way because thats how the 4thgen was stock.

the old impala/caprice... LT1 era stuff.. has EXACTLY what you want for cruise.
its a small box (little smaller then a MSD6A, same shape) with a cable coming out of it.
the cable goes to the throttlebody.
the inputs to it are very simple.. the VSS, power, on/off, accel, etc... and its an OEM cruise setup.

the 4thgen (and most newer cable throttlebody) setups are overly complex with saftey stuff, and become a big nasty ugly thing to convert in... the throttle by wire stuff however, is great.. no extra cruise control stuff needed, its in the PCM.

PCM provides power for the fuel relay
PCM provides Ground for the fan relays.

i dont know why they did the fuel one diffrent from every other relay in the car, but thats how it is... lol.. stock thirdgens and other GMs are the same way. i think its because older cars had the oil pressure saftey switch on the fuel pump, the standard was set, and GM didnt change it.

Man travis, i may have to bribe you to come up here and help me once i get the $ and parts to do my conversion!

I am really looking at doing this and you sound like you have the same thoughts as I do on where and what to do.. I want it to be like you say, like its supposed to be in there, but little else extra.. I dont like alot o fmisc. stuff everywhere.

Definately will be searching for more photos of your car too.