LS1 Swap Guide

LS1 Swap Guide

S13 with LS1 conversion completed by Barber Precision

What follows is a brief walkthrough of the steps of fitting a GM LS based Gen 3 or 4 small block V8 to your car. Of course every swap is different, but they all share a few bits and pieces in common so I will try to put it all together in one place with appropriate links to resources. I am not responsible for you injuring yourself, breaking your car, breaking your tools, dying, crushing yourself under an engine, or any other misadventure you may come under. This is just a rough guide - only do an LS1 swap if you feel confident you can do so safely.

Most of what I learned was from researching on the net and reading through other people's build threads. This is by far the best way to get started and I encourage everyone to research, research, research before embarking on a big project like an engine swap.

Speaking of which, take a look at the build log for my S13 Silvia here. I swapped an LS1 from a 2002 VY Commodore into a 1990 S13 Silvia without a swap kit. I did all the fabrication and wiring myself, which made it a very cost effective swap.

Step 1: Get an engine

LS1 and T56 engine dropout from a 2002 Commodore SS at Barber Precision

Of course you'll need an engine to do an engine swap, but don't just rush in and buy the first one you come across, you need to make sure you get the *right* engine.

Some things to take into account buying an engine:

Does it have the right sump/oil pan?

  • LS engines came with front, rear and mid-sump arrangements
  • If you're in Australia you will almost certainly get a front sump engine as this is what was offered in the Commodore
  • If you're in the US then f-body's came with rear sumps, which are probably the most common, however other vehicles did come with the other sump arrangements

What accessories does it come with? And are they in the right layout?

  • At a minimum you will need an alternator and some sort of tensioner
  • If you want A/C and/or power steering it will usually be cheaper if you can get these with the engine. It's things like these which drive up the price of your engine swap

Does it come with wiring? And/or an ECU?

  • The standard wiring harnesses and ECU's for the LS engines are usually easy to separate from the rest of the donor car wiring harness. It's almost like a standalone setup with a few plugs to connect to the chassis.
  • The standard ECU is completely tuneable with software such as HP Tuners or EFI live, however you may also go with an aftermarket ECU such as a Megasquirt or Haltech if you so choose.

What condition is the motor in?

  • A compression test, or better yet a leakdown test is a good idea on any engine you can't hear running
  • It's also important to check the oil. If it has bits in it and is clumping together it's a good sign the engine is toast

Does it come with a gearbox?

  • You have a few options for gearboxes. For a manual bolt-on option you have the T56 range of boxes or the later model TR6060, and in automatic you have a range of the 4L boxes.
  • With adapter plates you can now attach an LS1 to many other gearboxes to save the cost of an expensive Tremec box, however if you can get the engine and gearbox together as a bundle it will sure save a few headaches.

Ideally you want to buy a complete drop-out, which will include the engine, gearbox, wiring, ECU, exhaust, as all of this will decrease your costs and speed up your swap considerably.

I bought an entire Commodore from the local insurance salvage auction. The whole car was cheaper to buy than just a bare engine and gearbox from a wrecker, however I found out later it had a cracked head from the accident. It was only a $120 fix thanks to the cheap availability of LS1 parts, but was still annoying.

2002 Commodore SS donor car for the S13 Ls1 swap at Barber Precision

Step 2: Prepare the car

Assuming you have an LS engine (and hopefully gearbox) you now need to yank out your cars tired, presumably non-8 cylinder engine and prepare the engine bay. When you pull the engine don't forget to keep any sensors you may need with the new setup; I had to save the coolant temperature sensor for the gauges.

In my case, with the S13 being a fairly popular swap candidate, I knew I had to bash out the transmission tunnel significantly with a really BIG hammer to clear the T56. The extent to which you'll have to make room for the engine will depend on your specific car. If you can find someone on the net who's already done the swap - great! If you're the first one, then you're just going to have to test fit the engine and gearbox a bunch of times. Some cars don't need anything, and some cars need the entire firewall chopped out and a custom transmission tunnel made from scratch.

Step 3: Does it fit?

The moment has come, the step which will determine whether this is an easy swap or next to impossible.

With my swap I fitted the engine and gearbox in as one unit. The transmission tunnel was such a tight fit around the bellhousing that there was no way I'd be able to get to the bolts to attach the gearbox once the engine was in place. However if you have space (or if you intend on making a new tunnel) then it's fine to fit the engine by itself and fit the gearbox later.

Test fitting the LS1 in the S13 chassis at Barber Precision

A good idea is actually to remove the sump from the engine for the first fit and place some wooden blocks down on the subframe. If you start with wooden blocks the same thickness as your sump (+ a little clearance) you can get a rough idea of whether the engine will fit under the bonnet with the stock components.

One thing to watch out for on LHD cars is the brake booster loves to occupy the same space as the cylinder head/coil pack. Similarly on RHD cars the clutch master and head will try to become friends. I would advise either removing them or protecting them in some way against damage when you install the LS.

Starter motor clearance is an issue that can be overcome in a few ways. There are smaller starter motors on the market (I took this option) which can be clocked to put them even further away from the chassis. Otherwise you can buy kits to relocate the starter motor to the opposite side of the engine, though these are pretty expensive.

Step 4: Make it fit!

After the first test fit you should have a good idea what is hitting and what needs to move. This is the part where you take your BFH, your angle grinder, pick your tool of destruction and go to town.

Ideally you want at least 12mm (about 1/2") clearance between the engine and any other components of the car to account for movement on the rubber mounts. As a guideline the Australian National Code of Practice for modifying vehicles specifies a minimum of 10mm clearance between the engine and associated components and the rest of the car *when at full torque*. How you get in and measure how much clearance you have under full noise is a mystery to me, welcome to Australian car modding laws...

I would probably aim for a bit more clearance than that around the steering shaft, just because any touching there could cause your steering to bind up - not good.

As a rough guide I had to cut all the unnecessary "ears" off the gearbox to make it fit, bash the transmission tunnel until it almost split open, cut a chunk out of the sump and re-weld it, trim a bit off the top of the subframe for the exhausts and weld it back up, and fit a smaller starter motor.

Step 5: Make mounts

Engine mounts:
There are many ways to do the engine mounts, what follows is how I did it for my car. You will need a welder, angle grinder and drill press.
First you need a plate to attach to the engine block. Here is a link to the LS1 engine mount bracket template. I used 8mm mild steel plate.
Then you need an engine mount. I used land rover V8 engine mounts which are, basically, just a hockey puck looking thing with an M10 stud coming out each end.
You will a plate which attaches to the engine mount. Again I used 8mm plate steel.
Lastly (optional) if you don't want to use the factory engine mount location on the subframe/chassis you'll have to make something up from steel plate and weld it on.

Once you have these bits, the process is simple:

  1. Put your engine in the car (surely you've done this enough times now that it's easy, right?)
  2. Make sure it is level and centered. Do some research on driveshaft angle here, and here
  3. Bolt the engine plate to the engine
  4. Bolt the engine mount to the subframe
  5. Bolt your engine mount plate to the engine mount
  6. Make and weld in some structure to join the engine mount plate to the engine plate. I used square hollow steel tubing 3mm thick and it is plenty strong.

Hopefully that's clear. Essentially you bolt in all the bits you've made and join the engine plate to the engine mount plate with *something* strong, hopefully steel.

LS1 S13 custom engine mounts

Gearbox mount:
The gearbox mount, again, will depend on your car but they all basically look the same. There should be mounting points either side of your transmission tunnel.

You need a plate which bolts to these transmission chassis mounts, and you need a plate which bolts to the original LS gearbox mount. You then join the two together with RHS or plate, hopefully leaving room for your exhaust.

One helpful tip - the back of the T56 is threaded M10, and Landrover engine mount hockey puck things screw straight in. They are much stiffer than the original mount and much lower profile. I found it gave me more ground clearance than the original mount and was easier to attach.

Custom fabricated T56 LS1 gearbox mount to fit in an S13 chassis made at Barber Precision

Congratulations! Your LS is in the car

Step 6: Exhaust

The exhaust can be difficult to fit, given your car probably came with a piddly little inline four, and it can be a challenge to snake the drivers side exhaust around the steering shaft.

Custom extractors/headers are the best way to do your exhaust, but they are expensive/hard to make yourself.

Instead, here's a forum thread showing pictures of OEM manifolds which you may be able to use to make an exhaust.

If you find a manifold which *almost* fits but not quite, then you can 'angle mill' the flange to kick the outlet in towards the block or out away from it. I did this in order to use the standard commodore manifolds on my S13 and it worked really well.

Milling a commodore LS1 exhaust manifold on an angle to fit on the drivers side of the LS1 swapped S13

Once you have the manifolds sorted the rest of the exhaust should be fairly easy to work out (if not to fabricate). Expect to have to hammer out the transmission tunnel and potentially flooring to clear a decent size exhaust.

Twin 2.25" exhaust or a single 3" exhaust is fine for a stock or mildly worked LS1. If you do any serious work expect to see gains from a twin 3" system, though be aware this will be significantly louder. An X-pipe crossover will give the most top end, an H-pipe crossover will gain a small amount down low (some say it sounds cooler) and no crossover will sacrifice some power and sound like an old farm truck. I ran no cross-over for a year and loved it but would now go H-pipe for the power gains and cost over an X-pipe.

Step 7: Intake

Typically an LS swapped car is a bit starved for room at the front (along with... everywhere else) so sometimes making an effective intake can be difficult.

The best types of intakes are a straight shot over the radiator to pick up cool air and have no bends to cause restriction. From what I've researched a straight intake can be worth 10-15hp up top as compared to a 90 degree one, though I'm not sure I believe that. My swap uses a 4" intake with a 90 straight off the throttle body and it doesn't look like it has any real restriction, but I am prepared to be proven wrong.

Custom tig welded aluminium airbox to suit LS1 S13, fabricated in house at Barber Precision. Houses an original Commodore/GTO air filter

Step 8: Cooling system

The LS engine will likely put more demand on your cooling system than your original engine so an upgraded aluminium radiator is a good idea. These can typically be found cheap on eBay, or you can go with a brand name if you want something a little better in quality.

I've only used sub $150 radiators from eBay on all my cars and never had a failure, though I've heard of people getting 2 leaking ones in a row. It's up to you if you want to take the risk.

Try to find off the shelf hoses that fit with your radiator, and be sure to make a note of the part number so if you need to replace them you'll have it handy.

One other thing is if your gauges have their own coolant temp sensor, you should find a place to put it into the cooling system. I drilled out and tapped a hole in the cylinder head and screwed the sensor directly in. It's not in the coolant but it does measure the temperature of the head - this is not ideal but it does get the gauge working.

Step 9: Wiring

I'm not going to supply wiring diagrams for each and every LS setup around, but with enough searching you WILL be able to find the correct one on the internet for free.

However - some basic ideas:

  • The LS wiring harness should have 3 or 4 plugs which connect it to the body harness of your vehicle. These should be the only wires you need to consider when wiring the LS harness into your car
  • Power wires are what will trip you up. In my case the Commodore LS1 engine harness had 8 power wires, and the S13 didn't have the required number of fuses to supply all the current needed. I used the Commodore fuse box, cut down slightly, and a generic relay to switch power on from the battery when the ignition is on.
  • Don't forget the reversing light switch. In my case that sensor wasn't part of the engine wiring harness so I just wired it straight to the original reverse light switch wires
  • The fuel pump issue - the LS based engines use a switched 12v trigger to activate the fuel pump relay. In my S13 the ECU grounded the fuel pump relay when it wanted to activate it. There is an easy fix; basically your fuel pump relay coil terminals will have 12v on one side and the ECU on the other. You need to change it so it has ground on one side and the ECU on the other. This way when the ECU triggers the relay, current will flow through the coil and supply power to the fuel pump.
  • VATS - if you're using the standard ECU you will have to disable VATS (the GM immobiliser setup). You can do this with HP Tuners or EFI Live, or you can send your ECU away and for a small fee someone will disable VATS for you.

And then you're done, easy!