{Compiled by member cam- . If you have comments or suggestions, PM cam- or a moderator.}

Overview

The LS1 third gen marriage is a popular swap and offers some great benefits over traditional third gen power trains. The LS engine family is proving itself to be the engine of choice for modern day gear heads and few cars are exempt to receiving LS1 swaps from Mazdas and Austin Minis, even to the beloved faithful Ford Fox body crowd swapping them in. This swap is not considered cheap, so please review the costs links below to give yourself an idea of what to expect. To ballpark guess it on the absolute low end roughly $3000 USD would cover a stock LS1 swap, although banking on at least $5000 would be more realistic. Luckily for us third gen guys it’s a reasonably straight forward swap. There are basically four major aspects to deal with: 1. Engine/trans installation; 2. Exhaust; 3. Fuel; 4. Wiring. There are also many minor factors depending on the direction you decide to take, most of these points are covered in detail below. All of the parts necessary to bolt the engine into a third gen and get it started are now available for sale from various vendors if you get stuck you are covered. You can one-stop-shop at Hawks that many of us have dealt with and recommend, and he’s also a site sponsor (see link below). If you are wanting to take on more of the challenge yourself you can part and parcel the pieces together yourself from various sources like the parts for sale section here and over at LS1tech depending on your wants, needs, budget, and goals. If you are a reasonably skilled wrench with a decent set of tools then very few additional items need to be purchased - you can merely build them yourself, but a welder and fabrication skills are mandatory for the required modifications - or at least a good friend with these.


Is it really worth swapping to an LS1?
Decide for yourself - it’s really up to you to answer that - but here’s a thread of vastly varied opinions about the pros and cons from our board members. All I can say for certain is everyone who has done this swap is very pleased with the results.
https://www.thirdgen.org/forums/ltx-...1-instead.html

Costs - what am I in for?
https://www.thirdgen.org/forums/ltx-...-t56-swap.html
https://www.thirdgen.org/forums/ltx-...ice-lists.html
https://www.thirdgen.org/forums/ltx-...wap-costs.html

Hawks third gen LS1 conversion parts
http://www.hawksthirdgenparts.com/ls...sionparts.aspx


Where to start?


First thing you need is obviously an engine and transmission. All LS engines are externally the same regardless of origin. Whether it be from a truck, F body, Corvette, or GTO, they are all the same architecture, although there are vast differences in accessory drives, intake manifolds, and oil pan configurations. Being that the fourth gen and third gen f-bodies are so similar in so many ways, it is by far the easiest to swap a complete fourth gen f-body LS1 drop-out into your third gen. The accessory drives all fit under the hood and the oil pan clears. Truck engines offer only a usable long block and wiring harness as the oil pan, accessories, and intake manifold all need to be changed to fit into the third gen engine compartment. Corvette oil pans also do not fit and although the accessories fit it is not as good a match as a fourth gen set up. At the present time we are not certain of GTO pieces, so if you go this way post up your results. Worth noting that Corvettes use a transaxle set up so the engine is all that is usable.

This link has a bunch of good, basic information, and a lot of GM part numbers (dial-up warning - over 5Mb):
http://www.blackfbody.com/media/LS1_Engine_Kit.pdf

Got my engine and trans, now what?

This is now one of the most important elements you need to deal with. How much performance do you actually want? In stock trim the LS1 already has enough power to break parts with traction, so if you decide you want to start modding for more power at this stage of your build then it is essential to consider the other elements the car will require to be able to actually use the power and limit your breakages. Keep in mind that once you start with performance upgrades a good tune is also going to be in order, so do your research as to what you want and what you can afford and make choices at this stage wisely to ensure you get a safe, usable, drivable combination for your car that doesn't put you in the poor house.


Dropping the engine in the car... or should I say the car on the engine.

Seeing as the LS1 does not simply just bolt right in you need to make some decisions here about what to do. If you are planning on keeping A/C, the stock K member will need modifications such as these (see links below) or you can buy a tubular K member from Hawks or Spohn already made with LS1 mounts. The K member route is certainly a nice upgrade when you consider there is further weight savings and it allows a lot more room to work around the engine over stock but there is a pretty big cost involved. Modifying your stock K member is pretty easy if you have a welder and it’s also very cost effective. The downside to using your stock K member whether or not you run A/C is the oil pan to K member clearance at the back is tight... VERY tight, so it makes dropping the engine in from above very challenging. Many of us have simply removed the K member from the car and bolted the engine onto the K member, and then dropped the car over the entire assembly. As for A/C there is another option available from a few sources where you can re-use your stock third gen A/C compressor with brackets and mount in a similar position to stock. If you run the fourth gen compressor you will also need to fabricate lines. Engine mounts can again be purchased or made. The most popular and easiest way to bolt in your new LS1 is by using the fourth gen engine side of the mount and buying the horseshoe adaptor mounts from Hawks or Spohn. There is very little clearance between the coil packs and the heater box assembly on the passenger side. Some modified the heater box to clear and others used truck coils as they mount higher on the valve cover. Some managed to squeak it in there without modifications but it is tight regardless. The throttle cable must be changed over to a NON traction controlled ‘99 fourth gen LS1 cable. It fits nicely through the stock third gen hole although you will need to bend your stock third gen gas pedal arm outwards to take up the slack and use a large washer and some tie wraps to mount the grommet to the firewall as it is smaller than the stocker. Drive by wire Corvette swaps have also been done without much grief. The stock third gen radiator is ample and even bigger than the factory fourth gen LS1 radiator, so it is fine to use along with either a stock single or dual electric fan set up. You do need to hook up the steam line that comes out of the top of the heads via a small tube beside the throttle body. It is meant to be routed to the highest point in the cooling system to relieve the steam that can build up. If this is not connected you run the risk of cooking your new LS1 so be careful here.

Notching K member for A/C and lines
https://www.thirdgen.org/forums/ltx-...ompressor.html
https://www.thirdgen.org/forums/ltx-...-question.html

What coolant hoses to use?
https://www.thirdgen.org/forums/ltx-...se#post3442385
https://www.thirdgen.org/forums/engi...lower+rad+hose


Engine's in, now onto the transmission

The stock third gen transmission cross member will not work so again you can either buy a conversion piece or build one up. The best option currently available for a nice fitting cross member that allows decent clearance for your exhaust y-pipe to clear without hanging low is from Hawks Third Gen (4L60E and T56 each have their own version). If you are running an automatic its a pretty straightforward bolt in as far as your shifter cables and cooler lines go they should all fit with tweaking and all the shift points and overall function of the transmission are controlled through the LS1 PCM. It is possible to mount the LS engines to traditional SBC transmissions but is not really advantageous unless you are going for a TH400 or TH350 set up that is a drag car only. The 4L60E is an electronically controlled 700R4 with a beefed up case and works in harmony with the engine management system so this is what most do for automatics plus it has the tail shaft to accept the torque arm bracket. For manual set ups you will need a complete hydraulic system (master, line, slave) from a fourth gen. There were issues with the early systems so make sure you get 2001 and newer hydraulics. Stock third gen manual pedals will work but you need to drill out the bushing from the LS1 master, or repin the pedal, to make it fit perfectly, or you will have disengagement issues. Some others have swapped in LS1 pedals with good success and they are readily available cheap. All T56 shifters are the same although some fit third gens better than others. The stock fourth gen shifter will work. If you’re going from automatic over to manual you will also need to cut a hole in your floor pan for the shifter. For speedo hook ups both stock LS transmissions utilize a VSS electrical output so if you have a mechanical speedo in your car you will need to change it or get the mechanical drive box available from Hawks http://www.hawksthirdgenparts.com/in...ROD&ProdID=906 . If you have a factory electronic speedo it will work although you may need to modify the parameters in the PCM to send the correct signal to make it work. There is also a company called Baker Electronics that make a Dakota digital interface box that can be used to send the correct signal for your speedo.

Also note that while the 3rd gen torque arm will mount to the 4th gen transmission mount, you will have to use the 4th gen mount itself, because the 3rd gen torque arm mount will not bolt to 4th gen transmissions.



Okay the engine/trans is in now to hook up the exhaust

Stock fourth gen LS1 manifolds will fit and actually do a fine job as far as manifolds go. There are two series of these and both fit, although the second design (2001 and newer) perform as well if not better than shorty headers, so it’s manifolds or longtubes to be decided here. Longtubes are a solid upgrade for LS1's even in stock trim they can add substantial gains but sadly fourth gen front frame designs are radically different and NO FOURTH GEN headers will fit a third gen so don’t post about this - they don’t work period. As of this time there are two quality long tube options available for us: 1) Hawks Stainless Works - They are top shelf pieces, the fabrication is truly second to none and the performance limits are waaaay up there. Of course the downside is the cost - they are not at all cheap at $800.00, so your call. There is a y pipe available but they have been known to be very poorly built and designed so consider yourself warned about the y pipe, you will probably fare better if you build your own or have one built. And, 2) Hedman now has 1-3/4" & 1-7/8" longtubes available - no Y-pipe. If you run manifolds you have to build a y-pipe yourself or farm it out to an exhaust shop as there is no current option for sale. Once you get your manifolds/headers and y pipe figured out the cat back is pretty straight forward from there, although plan on having to make an intermediate pipe to connect it all up. See links below for exhaust set ups. (Note: There are some really cheap-looking long tubes that have been seen on eBay, but as always, you tend to get what you pay for.)

y pipe links
https://www.thirdgen.org/forums/ltx-...our-ls1-y.html
https://www.thirdgen.org/forums/ltx-...ry-thread.html
https://www.thirdgen.org/forums/ltx-...2-my-87-a.html


What about fuel?

The absolute easiest is to use your stock third gen tank and add a fuel pump capable of delivering enough fuel and a regulator to manage it. Again Hawks sells a complete kit for this to make things easy. It should be noted that the LS1 engine demands a much higher fuel pressure of 61psi than third gens do at 42psi. Early C5 Corvette fuel filters have a regulator built in for those looking for a cost effective route for a regulator. As an upgrade a complete fourth gen LS1 fuel tank will bolt in with minimal effort although you will need to run new fuel lines or at least modify your own to fit. There are some solid advantages to using an LS1 tank as it has a bucket surrounding the pump to keep it cool and prevent starvation as well as a built in charcoal canister and a pollution friendly evap solenoid, and the added bonus is they have a built in regulator. The gauge sending unit operates at a different ohm sweep than your stock third gen gauge reads so a new sender will have to be installed to make it read correctly however. These links cover all what you need to know for this

Fuel system links
https://www.thirdgen.org/forums/ltx-...k-plastic.html
https://www.thirdgen.org/forums/ltx-...-ls1-fuel.html
https://www.thirdgen.org/forums/ltx-...ank-ready.html
http://www.ls1tech.com/forums/showthread.php?t=558819

 

Now the real fun begins.... WIRING!!!

This is certainly the topic that comes up the most frequently when concerning LS1 swaps and retaining the stock PCM controlled engine management. It seems daunting from the outset and for those of you concerned about doing this yourself, not to worry there is a huge amount of support available for stand alone wiring harnesses. Hawks again sells conversion harnesses. Speartech has earned the reputation as offering high quality plug and play harnesses and the double bonus of top shelf technical support. Painless also offers plug and play harnesses for LS1 swaps and some swear by them. These are reputable, easy to use solutions for those looking to move past this final step with ease, BUT as with anything there is a cost and it is not cheap. Expect over a thousand dollars here for true plug and play happy happy joy joy. There is also a carburetor option from a few sources now, both Edlebrock and GM have solutions if you want to avoid fuel injection altogether. The Edlebrock system is easy to install and use and makes great power. However, if you wish to tackle the wiring yourself its really not as bad as you might think. The conversions hybrids sticky (link below) over at LS1tech has invaluable information covering many different model platforms, pin-outs, and diagrams to help you along. There are countless posts about this and one can become easily confused by pouring over all the questions and technical jibber jabber that is necessary to find solutions, but I promise you if you follow these simple steps you will be on top of it in no time. What you need to do is pretty straight forward: Connect the LS1 engine harness to your third gen stock Chassis harness. To do this you will need the pin outs for both your car and your engine. It only takes 6-8 wires to connect together to make the engine start and run. The rest are simply to make your accessories work like gauges and A/C if applicable, etc. The challenge is just weeding through which of the 8 wires to connect. Worst case scenario is about 25-30 splices if you have a carb car to start with and keep A/C and all accessories. Here’s a quick breakdown of the process;

Get the pin outs from your engine;
http://www.ls1tech.com/forums/showthread.php?t=312119

Get the pin-outs for your car. You might be able to find these here on TGO or you can go buy the Helms, Chiltons or Haynes manual and source them yourself. Once you have all the pin-outs form both your engine and car make up a spreadsheet similar to this;
https://www.thirdgen.org/forums/engi...s1-wiring.html

Once you have done that you will have determined what circuits you need to keep and what to remove. Easiest way to avoid any mistakes is to label every wire on your engine harness and your third gen harness. Starting one wire at a time either cut it out if it’s on your delete list or hook it up to where it goes. You will need basic wiring supplies for this including extra wire. Sourcing wire is easy if you take a trip to the wreckers and buy a harness out of another GM car that’s clean. Solder, heat shrinks, and harness tape are highly recommended to avoid gremlins later. You will need to add in a few new circuits with relays and fuses depending on your set up and what donor car you start with. The VATS will also need to be disabled to get it to start and that can be done via a VATS bypass module which is a low cost little resistor box from Hawks or through a tuning software like HPtuners or EFIlive. Through the course of third gen F body production the wiring changed considerably from 82-92 so there is no set schematic for you to follow - you will have to make that up yourself. For those of you planning on doing up your own harness there is quite a bit of reading involved to get it right and a fair bit of effort and time to make a quality harness that is neat and functions well.
https://www.thirdgen.org/forums/ltx-...ll-engine.html

See this link for pics of where to drill the hole and how to mount PCM under dash just keep in mind to make sure you USE A RUBBER GROMMET in the firewall unlike some of the pics posted in this link as that is very risky not to.
https://www.thirdgen.org/forums/ltx-...ing-under.html

LS1tech and TGO are great resources and pretty much all the issues you will face have been covered before, so before posting up and finding no one to help use the :SEARCH: feature!! This will be your savior for anything not listed above. I'm sure we will update this as more good info comes along but this is a good start and should get you 90 percent of the way home. Good luck

cam-

 

A few more wiring threads:

https://www.thirdgen.org/forums/ltx-...p-3rd-gen.html
https://www.thirdgen.org/forums/ltx-...ml#post4305264
https://www.thirdgen.org/forums/ltx-...revisited.html
https://www.thirdgen.org/forums/ltx-...formation.html

 

If you are thinking of starting with a LS-based truck engine (4.8, 5.3, 6.0, 6.2):

https://www.thirdgen.org/forums/ltx-...otor-into.html

An article about drilling and tapping the missing accessory hole for f-body accessories on a truck block:

http://ls1tech.com/forums/conversion...nator-diy.html

 

Good article on the basics of the LS-family of engines:

http://www.hotrod.com/howto/113_0504...ics/index.html

 

Some member photos are posted here:
https://www.thirdgen.org/forums/ltx-...-lsx-swap.html

 

From member 1ADan:

Some useful part #'s:
12557752 oil pump seal (always replace when you change pick up tubes)
12570326 GM Cylinder Head Dowel (missing on my shortblock)
12498545 97-03 head bolt set (per head) GM normally sells per bolt
17800568 04+ head bolt set (per head)
12602548 Coolant crossover pipe LS3
12605716 Coolant crossover pipe L92 - using this on the rear of mine
12602540 Coolant Caps (need 2 if your going to block off the rear)
12551933 Coolant Seals, Head (each) - use for sealing crossover pipes
12577927 newest LS6 valley cover (with bolts and gasket included)
12594779 pcv (or lack there of) hose for LS6 valley cover conversion
12610046 6.0/6.2 head gasket (each) - low cost, high quality MLS

 

An inexpensive alternative for a 4" MAF, courtesy of 1nasty86:

https://www.thirdgen.org/forums/ltx-...r-own-4-a.html

 

Article with good information about various LS accessories:

http://www.carcraft.com/techarticles...e/viewall.html

Thanks to TGO member sailtexas186548 for pointing it out.