LFX Engine Swap (GM V6) at GWR

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Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

With the engine buttoned back up, first test fit in the engine bay!
LFX test fit.jpg
iniazy
Posts: 8
Joined: Fri Mar 30, 2012 10:13 am

Re: LFX Engine Swap (GM V6) at GWR

Post by iniazy »

Awesome build!
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Transmission and differential!

With the engine in place I can finalize placement of the rest of the drivetrain downstream.

Utilizing V8Roadster's frame rails and transmission crossmember which are intended for the GM MV5 (Camaro) and MV7 (Cadillac CTS) transmissions. The frame rail braces are great additions to just about any Miata because the factory rails are thin and get damaged over time, so it's a win-win to add these and have a mount for the transmission that is already figured out for us:
V8R Framerails and Crossmember.jpg
**Note the ratcheting strap: the chassis is strapped to the lift front and rear, with everything down to the subframes going in/out multiple times you don't want to need to keep track of how much weight is on each end of the car so it doesn't fall off the lift!

Transmission bolted up without issues. The transmission's rear mount bolts to the V8R crossmember which ties in with the frame rails, so leave the frame rails unmounted until you have the transmission bolted up to dictate their placement, and then drill and bolt the frame rails in.

V8R uses an energy suspension poly bushing in the rear trans mount. Here's the mount bolted up without the crossmember in place:
MV7 Crossmember Bushing.jpg
Here's the crossmember added. MUCH better ground clearance with this transmission than the T56s in the V8 swaps. :)
MV7 with crossmember mounted.jpg
Even with bolt-on parts sometimes there is a need to tweak them to work for your car, and here was a good example of that. Because this kit was designed around an NB, the crossmember interfered with the passenger side corner of the transmission tunnel and floor on this NA, which you can see in the above pic.

Looking at the pic below, taking this notch out of the crossmember fixed the interference and then everything could square up:
Crossmember notched.jpg
With the crossmember bolted up, the framerails could be bolted in their final resting place. Lots of drilling and then torquing bolts (2 person job - one person in the car with a wrench on top):
MV7 Installed.jpg
Checking the transmission angle. It's sitting at 1.7° nose-up here. With the rear trans mount torqued down it cinches down to 1.6°:
MV7 angle.jpg
Moving on to the diff!

V8R's diff mount kit includes a bracket that bolts to the two ears on the back of the Getrag diff which then slide up on to the same two long studs in the rear subframe that the Miata diff bolts to. The kit also includes two bare steel tabs that get welded to the subframe for the Getrag's front mount:
Getrag mount kit.jpg
V8R's instructions are to weld the front mount in so that the pinion angle is 1.5° nose-up, which looks perfect now that we know the transmission's angle.

Bolt the rear mount to the diff and then bolt that to the subframe. I forgot to specify I wanted the diff's factory mounting bolts when I got the diff from the yard so I had to source some - they're M14x2.0, two 45mm long for the rear and one 90mm for the front plus lock washers for all three and a nut for the front.

The rear mount has roughly the correct angle preloaded into it, so with the diff mounted to the subframe you just shim the nose as necessary to dial in the exact angle. I needed to shim the nose down a bit, you can see the shim stack in the background of this pic:
Getrag front bushing 1.jpg
Also pictured is the fun discovery that the front factory bushing was completely shot - it just popped out in my hand. Obviously this had to be replaced. Despite most of the bushing already being out, the tough part of the bushing removal was still to be done. You have to remove the steel sleeve that the bushing was once connected to. It does not come out gently:
Getrag front bushing 2.jpg
The factory design is prone to fast wear under hard use because it's soft and has a lot of air gap around the center sleeve. On a street car you'll want the factory bushing (Moog PN K200641), but for track use I chose a polyurethane replacement. There are a couple on the market, I settled on one from Creative Steel - this is the "street" durometer which is 75A. We air-hammered this in which was nice and easy. I don't envy someone trying to press this in considering the proximity to the housing:
Getrag front bushing 3.jpg
With that lovely side-track behind us, back to the front mount...

The two steel front mounting tabs are a "starting point" but need some grinding to clear the housing better. The front just got a bit of clearancing on the outer radius by the hole. The rear tab needed to be notched:
Getrag front mount 1.jpg
More than one way to tackle setting the pinion angle prior to welding, my method to eliminate variables as much as possible was to set the whole assembly on the bench and shim the subframe to dead level and then shim the diff to the 1.5°:
Getrag angle 1.jpg
Then tack-weld the tabs in place:
Getrag front mount 2.jpg
Rear tab tack welded in, you can see why the tab was notched:
Getrag front mount 3.jpg
These are tack welded ONLY at this point. Always test fit in the car and measure before finalizing. The car might not be dead level on the rack or jack stands, and that transmission angle that was measured is relative to actual horizontal, not to the car. Measure many, many times and weld once.

Turns out, the car is level on the rack :idea: Diff sits at 1.5° nose-up, matching the transmission's angle within 0.1°:
Getrag angle 2.jpg
Subframe comes BACK out again, and final welding can happen. Diff is removed from the subframe for this of course. I cut a length of steel tube to match the length of the diff's front mount and bolted that between the tabs while welding to prevent warping. Don't leave the diff in there to serve that purpose, you'll melt the bushing.
Getrag front mount 4.jpg
That's it! Subframe will get cleaned and painted now along with some other parts.
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Camaro gas pedal conversion

The LFX, like most engines these days, is drive-by-wire. That sounds good to me since I've lost a couple throttle cables over the years from nearby turbo heat. Naturally, the Miata pedal fixture needs some modification to accommodate the GM pedal.

The first and always lovely step was of course removing the drivers seat and spending what felt like an eternity removing the pedal assembly from the car while being jabbed in the back by harness eye bolts, seat brackets, etc. etc.

Stock gas/brake pedal assembly clamped to the table with some alignment marks for pivot point and such, and Camaro pedal nearby:
Pedal Conversion 1.jpg
The Camaro pedal is very similar to the Miata's in some ways such as length, angle and travel. However, the mounting layout is entirely different of course so a custom mount is needed in order to place the new pedal in just the same position as the one it replaces.

Stock pedal removed and unneeded mounting fixture cut off leaves the assembly on the left, plus a new additional mounting plate for the Camaro pedal to be welded on:
Pedal Conversion 2.jpg
The added plate welded on as well as a brace along the top to help keep the mount from flexing and studs added:
Pedal Conversion 3.jpg
New pedal mounted up. Pedal position matches the old setup with identical pivot placement and angle.
Pedal Conversion 4.jpg
With it finished, the fixture was bead blasted and powdercoated. Ready to be re-installed:
Pedal Conversion 5.jpg
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Location found for the SMI water temp gauge's sensor in the engine. This port is plugged with an allen head bolt, confirmed it goes to a water jacket because I got a face full of coolant when I pulled the plug despite having had the motor upside-down a dozen times..

That port is 1/4 NPT threads so with a 1/8 NPT Female to 1/4 NPT Male adapter the sensor fits perfectly.

Right side of the block:
coolant sensor.jpg
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Alternator on the LFX had a bit of a clearance issue - the stud on the back contacts the V8R subframe. This specific motor/alternator was a 2012. I've heard from others with 2013 donors that the stud layout was a bit different so not everyone will run into this.

Solution we came up with was to clock the alternator. Four M4 bolts holding the front and rear together (remember to mark the studs position before clocking), then remove the plastic cover on the rear and finally remove the small plastic cover over the brushes in the center on the back:
alternator 1.jpg
Pull the two halves apart, rotate the assembly 180° and drop them back together. You have to push the brushes in for the center shaft to slide all the way back in.

With the alternator clocked, the stud is nice and far away from the subframe:
alternator 2.jpg
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

The finished subframe is back from powdercoating and looking good in 60% gloss black:
Getrag_Subframe_powdercoated.JPG
Diff gets installed once again and now the assembly is ready to go in the car:
Getrag_Subframe_Mounted.JPG
Before we can install this though, we'll need to get the fuel lines installed with the tank and the tank back in the car.
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Fuel Lines

V8Roadsters supplies a very nice fuel line kit for the LFX. Very similar to their kits for V8 cars, it includes a Corvette filter, EFI fittings throughout, and assembled braided lines to replace all the factory lines in the car:
FuelKit (2).JPG
Dropped the fuel tank and took a look at things. The EFI fittings are very cool but they only work with the later-year fuel hard lines. Not a problem at the engine side because the LFX has the correct lines, but at the tank things need to be switched around since mine is an NA, so I need to swap to NB bits there.

We had a junker NB sitting beside the shop, so I pulled the fuel pump assembly out of that. With a little mix-and-matching of parts and swapping over my Walbro 255lph pump to the NB fixture it's good to go:
FuelKit.JPG
Using the NB's fuel pump fixture, the EFI fittings fit the hard lines perfectly:
FuelKit (5).JPG
Lines attached, the tank is ready to go back in.. this pic is after lots of scrubbing of the fuel tank to get it clean:
FuelKit (4).JPG
With the tank reinstalled, all that's left is to mount the filter and lines. Made a small bracket to hold the filter in place (don't have a pic of it), and the lines are routed along the inside of the frame rail. V8R says that they typically run the lines down the driver's side, but I found that running them down the passenger side I was able to shorten the line length by 12" (the easy route is to leave the line as-is and run down the driver's side):
FuelKit (3).JPG
Close-up of the attachments for the fuel line - these adel clamps are included in V8R's kit. This is the front-most mount, I added the small stand-off to move the line away from the frame rail so it cleared the hard brake line that you can also see running behind it, which I ran at the same time:
FuelKit (6).JPG
The end of the line curves up over the transmission and attaches to the LFX's fuel hard line and that's it, fuel system is done.
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Cooling system

Time to get the radiator sorted out. A lot of components in the nose have to mingle together nicely, so there was a lot of figuring out several systems at the same time in my head before finalizing anything.

Now, this is where we begin to really digress away from your 'typical' LFX build, and why the time investment and costs of this build are a lot higher than someone could typically swap an LFX for. I'm still sharing everything because I think it helps give guys ideas and shows what you could do.

The EASY option for a typical build will be to use V8R's radiator which drops into the factory vertical position:

Image

Now, with that said, let's move on :mrgreen:

On this car the plan is to vent all the air that goes through the radiator up and out the hood via a large duct. This will maximize radiator efficiency and also reduce aero lift significantly. I also have plans for an intake that needs to extend over the top of the radiator, so for these various reasons we want to tilt the radiator forward quite a bit.

Based on that, I chose to center everything around our GWR triple-pass radiator for the NC chassis. NC radiators are already designed to be tilted forward so the brackets on the unit don't need any modification, and the NC units have 30% larger surface area than an NA/NB radiator - and we want all the cooling we can get at the racetrack.

Image

Of course, all of the mounts for the NA's radiator need to be discarded (cut out) and new brackets need to be made.

Here are the new lower brackets which cradle the radiator's bottom posts. These also have threaded locations to mount some of the air ducting that will come later:
Cooling.JPG
The radiator's top mounts tie in with a new cross-tube that runs laterally between the two frame rails. Designing this cross bar, I want it to be removable to make engine removal/install nice and easy, so that involved welding captive nuts inside the frame rails for it to bolt to (which took some creativity :wink: ). The radiator, intake, power steering cooler, and some of the air ducting will all tie in with this cross-bar:
Cooling 8.jpg
Cross-bar installed with the radiator in place. The radiator's upper brackets mount to the two outer threaded points on the bar, via rubber standoffs to isolate vibrations:
Cooling 7.jpg
With the radiator in place we can look at the main coolant feed and return lines.

In the few LFX swaps that are out there so far, everyone's re-used a factory GM return line, but because I'm using an NC radiator which has the feed/return on the correct sides of the radiator to match the LFX (as opposed to NA/NB rads which are opposite), I could actually make use of the more direct and simplified routing that this makes possible. But, that means I need to make a new return line...

Here's the new return line made with aluminum mandrel bends and beaded ends:
Cooling 9.JPG
Installed with silicone couplers on either end (45° at the engine and a straight coupler to the radiator):
Cooling (5).JPG
The feed line is a bit simpler, needing only a pair of 90° silicone couplers and a short aluminum joiner between the two. However, the outlet from the engine is 1.5" and the radiator is 1.25" so one of the 90° couplers must be a reducer.
Cooling (2).JPG
Above you get a sneak peek of the intake, which I'll cover in the next post :D

Also pictured above, I'll be using one slim SPAL 12" fan for the lightest weight possible. This will only get used while idling in the pits, won't need it when the car is up to speed and this car won't ever be sitting in traffic:
Cooling (4).JPG
All that's left is to sort out the expansion tank (radiator is no longer the highest point in the system) but that will be tackled in a few weeks.
Ryan @ GWR
Posts: 497
Joined: Fri Oct 17, 2014 11:37 pm

Re: LFX Engine Swap (GM V6) at GWR

Post by Ryan @ GWR »

Intake time!

The EASY method that will work for most typical swaps is much like V8Roadster's street NB:

Image

90° bend out of the throttle body (3" diameter) over to a filter location on the driver's side behind the headlight. For the air sensor you could use a coupler like this:
https://www.amazon.com/Spectre-Performa ... nk21197-20
Or this one which is a weld-in:
https://www.summitracing.com/ga/parts/n ... erformance

Now that we've covered that, for this car I wanted to try out an idea I've had bouncing around for a while - putting the filter forwards of the radiator, and the tilted radiator makes this possible. Turns out, the angle of the throttle body is spot-on for this without even any bends, as if it was meant to be :D

Couple pics of the creation process...

Made the air sensor flange from scratch:
LFX_Intake_1.JPG
Sensor is placed pointing down just ahead of the throttle body:
LFX_Intake_2.JPG
LFX_Intake_2.JPG (75.01 KiB) Viewed 20509 times
Intake tube in progress:
LFX_Intake_3.JPG
LFX_Intake_3.JPG (77.1 KiB) Viewed 20509 times
Bracket...
LFX_Intake_5.JPG
LFX_Intake_5.JPG (134.84 KiB) Viewed 20509 times
Supports the intake by the two center brackets on the cross-tube:
LFX_Intake_4.JPG
Notes on filter choice - the math says this motor needs about 460 CFM of intake flow. I like to oversize the filter by about 20% so shoot for a filter with 550-ish CFM. You can call K&N and get flow specs on any filter in their catalog if there's a particular shape/size you want to use.

Finished up:
LFX_Intake_6.JPG
Why this position?

I like this for a few reasons; While this car makes judicious use of vents to reduce both pressure and temperature under the hood, under-hood temps are still a good bit higher than the ambient temp outside even on the hottest days. Cooler air means more power with less chance of detonation - placing the filter ahead of the radiator means the engine gets ambient temp air all the time without the need for any additional ducting.

Second, the bumper mouth is the highest pressure area on the car at speed - particularly for race cars with tightly sealed ducting. While this is just a fraction of the kind of pressure a turbo or supercharger creates, at very high speeds it can add a few more hp, and every little bit will help at high speed tracks where we're pushing against aero drag somewhere around 150 mph.
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