GM LFX 3.6L V6 Motor Swap

[kurty85]

Originally Posted by gtpvette

Good news, Bad news. First the good. First two shots are the motor mounts in their current state. Overall look like they'll be fine. I did trim off a bit from bottom the plates that bolt to the motor and they're a little shorter than I'd like. I want room to weld both the top and bottom of the plate that attaches to the rubber isolator.


I've gotten then motor close to where it needs to go. I put a 1/2" wood spacer on the cross member and steering rack to space the motor up. I hope 1/2" is enough. Motor mounts locate it side to side then 1.5 degrees down toward the rear end. The back of the motor (less the HP pump area) has plenty of room and shouldn't be an issue for AC or heat. I did trim the heater tubes coming out of the firewall a little. The motor is not as tall as I was initially afraid of. I will need to modify the hood but not too much. Mostly for the front of the intake and TB.


Bad news is the clutch master cylinder. With the motor moved as far forward as I can at this point (back of oil pan right up to rack) I still don't have enough room even without the hose and banjo bolt on it. I have less than a fingers width available. I figure I need about an inch more. I'm going to trim the oil pan a bit so I can move it forward some and I may recess the clutch MC a little more. I'm pretty sure I can get what I need there. I'll order the banjo bolts/fittings today so I can see what I need.

You can always move it to the right. I move mine. Used a 2 1/8" hole saw, reinforced it with metal plate, and used a 5/16-24 with 8mm hole spherical bearing rod end, bolt, and spacer on the clutch pedal actuation arm. Worked perfect and allowed me to move my engine back 3 more inches.

[gtpvette]

Originally Posted by kurty85

You can always move it to the right. I move mine. Used a 2 1/8" hole saw, reinforced it with metal plate, and used a 5/16-24 with 8mm hole spherical bearing rod end, bolt, and spacer on the clutch pedal actuation arm. Worked perfect and allowed me to move my engine back 3 more inches.

I cut the oil pan yesterday,,, but if that doesn't do the trick may just try it. Thanks!

[gtpvette]

Finished up cutting/grinding the pan last night,, will drop off at welders this morning. Basically cut off the curved section that joins the bottom of the pan to the back, you can see it in first picture. Have some 1/8" that will be welded over the opening. Hopefully I'll have it back by the weekend to see where we are. I only need an inch or so.

[gtpvette]

Finally got pan back from welding,,, took almost 2 weeks. All that and they forgot to weld up a bolt hole for the windage tray that is now open due to the cutting. It'll have to go back at some point to address this.

Good news is motor fits now. I did place the motor in and align as best I could. There isn't a lot of room at the clutch MC,,, but it doesn't rub even with the banjo bolt and fitting in place. Sorry forgot to get a picture of this.

I then tried to slide in motor and trans together for the first time. I needed to get motor aligned so I could tack the motor mounts and part of that is making sure trans is centered. Really tight trying to get the motor over the cross member and not hit the firewall. Bad news,,, trans wont clear the existing trans mount. It's a real shame as it's in the right location just to narrow. Pulled it out and started removing the trans mount. Others have warned about this,,, and yes,,,, it's a real pain in the ass. I got half out yesterday. I used the spot weld drill bit and cut off wheel. I'll try to get the rest done this week. I may just go ahead and remove the drive shaft mount as well.

[gtpvette]

Work continues but slow as I've been super busy at the office. Both transmission tunnel braces are out. What a PITA LOL. Broke a bunch more Harbor Freight bits so ended up finishing up using the 4.5" cut off wheel. If I was to do it again,, I'd just use the cutoff wheel. This weekend I should be able to tack up motor mounts and cut the additional braces for them.


Spent some time touching up the tunnel paint. Got primer, paint and clear from http://www.automotivetouchup.com. Color is OK not great though. I also got a can of Rustoleum Regal Red. For $3.50 it's pretty close which surprises me as the other stuff was $47. Tunnel doesn't really matter too much,,, but still need to touch up firewall. Not sure which way to go as of yet.


I need to order exhaust system or piping and wanted to ask your opinions before I do. I want run 2.5" pipe out of each exhaust manifold back to a Magnaflow resonated x-pipe right behind the transmission, then dual pipes (either 2.25" or 2.5") out to the back,, maybe some additional mufflers then tips. The question revolves around dual pipes all the way. Seems most V8 swaps run a single 3" as apposed to duals. I've seen at least a few exhaust systems that run duals at least under the rear cross member and out the back, the first is the Greedy CS GTS that runs a 2" pipe around one side or the Ptuning that runs a 3" pipe around both sides. What's the consensus regarding a true dual system. Doable or would I be creating a nightmare?


Lastly see attached file (SC.txt) for the latest costs. With selling the FA20 and Trans, I'm on track for $6K or so total.

[venturaII]

A single 3" is plenty of flow for a 3.7 liter motor and likely easier to find room for along the tunnel than dual 2.25/2.5 pipes. I'd join the two 2.5" pipes after the collectors, run 3" back to the stock muffler position and use either a transverse 3" in/out for a single tip exit, or a 3" in/dual 2.5 out for twin tips.

[brandons86]

sick build dude

[gtpvette]

Originally Posted by brandons86

sick build dude

I don't know,,,,, sometimes I wonder will it ever happen :-)

[gtpvette]

Originally Posted by venturaII

A single 3" is plenty of flow for a 3.7 liter motor and likely easier to find room for along the tunnel than dual 2.25/2.5 pipes. I'd join the two 2.5" pipes after the collectors, run 3" back to the stock muffler position and use either a transverse 3" in/out for a single tip exit, or a 3" in/dual 2.5 out for twin tips.

Based on the charts I've seen 3" seems to be enough flow although some warn that with bends and other restrictions may reduce flow. Dual 2 1/4" doesn't flow that much more and certainly would be a bunch more work. Still would like dual 2.25" if possible as I suspect it would sound better.

[venturaII]

If you have dual 2.25s or 2.5s, either way you're likely going to be using a crossover pipe, so there really won't be much difference in sound compared to a big single system. If a 3" single is enough to support a 350 cube, 5500 rpm motor, then I think it'd be more than adequate for a 3.7 liter 7000rpm motor. Also, while the chart above is a nice rule of thumb for squeezing every last possible peak horsepower out of a motor, keep in mind it's very likely the motor's midrange will suffer for it a bit.

[Summerwolf]

Originally Posted by gtpvette

Based on the charts I've seen 3" seems to be enough flow although some warn that with bends and other restrictions may reduce flow. Dual 2 1/4" doesn't flow that much more and certainly would be a bunch more work. Still would like dual 2.25" if possible as I suspect it would sound better.

Is what they come with dual 2.25? Either way, I would lean towards trying to emulate what the big exhaust makers do for the frs to begin with. You know it works, you could probably follow their design easily, or if you wanted to be lazy buy a catback meant for the car and make it work


There are multiple makes of 3 inch exhausts, just an idea. Heck the 4th gen LS1 guys generally do a large single pipe after a Y and they make plenty of power, so I think you'll be fine with the V6.

[Summerwolf]

Originally Posted by venturaII

If you have dual 2.25s or 2.5s, either way you're likely going to be using a crossover pipe, so there really won't be much difference in sound compared to a big single system. If a 3" single is enough to support a 350 cube, 5500 rpm motor, then I think it'd be more than adequate for a 3.7 liter 7000rpm motor. Also, while the chart above is a nice rule of thumb for squeezing every last possible peak horsepower out of a motor, keep in mind it's very likely the motor's midrange will suffer for it a bit.

A "Y" to single pipe vs cross over and duals sounds incredibly different. The crossover type also plays a part in that too.

[gtpvette]

Originally Posted by Summerwolf

Is what they come with dual 2.25? .

Camaro comes with duals,, starts as 2.5" reduces to 2.25". It has an H pipe, resonators then dual mufflers. LFX Camaro guys seem to like to replace H pipe and resonators with Magnaflow resonated x-pipe 11386, then either delete the mufflers or change them out. They sometime up the 2.25" to 2.5" as well.

[venturaII]

Originally Posted by Summerwolf

A "Y" to single pipe vs cross over and duals sounds incredibly different. The crossover type also plays a part in that too.

Not by my experience when using identical muffler brand/type, but YMMV. Most people compare Brand X single system against Brand Y dual system and they conclude the difference in sound is the configuration, not the muffler.