OptionXIII

I love seeing build threads like this where OP comes in with a lot of background on how they researched their decisions. As I continue to agonize over how I want to finally get more power in my chassis, it's great to be able to reference thorough build threads. Especially since my goals are much the same as yours - a car as capable of track days as it is commuting or long drives.

Looking forward to seeing more!

flatpick13

Perfect timing with the FWD parts links, I just picked up an engine from an impala over the weekend. Guy I got it from was planning on using it for a swap and then changed directions, so already has a brand new intake manifold, but I still have to do the accessory brackets, wiring harness, and all the little pieces. Also still have to source a PCM and pedal.


Do you think you’ll have it running to hit some mountain roads this summer?

BAgarage

Love the build and detail! Been thinking about lfx too. What year Impala we’re you looking for?

crxguy52

Thanks! I enjoy writing it up, so I'm glad it's useful to others.

You got that from a guy in SC who wanted to put it in an RX-8, right? I was messaging him on FB and he said he had someone else interested. Only reason I passed was because he was about 4 hours from me and wasn't super responsive. Didn't want to spend an entire day driving and have him flake. Congrats though, that's a pretty good deal. I was going to get the PCM from Keislier and the pedal from rockauto - scrapyards want ~75 for the pedal and it's like $80 new on rockauto. PCM can be had from scrapyards for about $75, but then you have to buy a HPTuners license.

I'd love to have it driving by this summer, but with the amount of work I have left I don't think it's reasonable. My goal was have it driving by the end of the year. From what others have said the exhaust and cooling system will probably take a while. I'm assuming you're also swapping it into a miata?

Thanks! Mine is from a 2016, but it came in a bunch of applications. When you search for any of those applications car-part will show you all the interchangeable cars as well, so it casts a really wide net.

flatpick13

Yep, got it from the RX-8 guy in SC. Took a few weeks, but I had an event in GA and was able to pick it up on the way home so it worked out. Not as low miles as yours but low enough I’m not worried about cracking it open beyond the valve covers and oil pan. Thanks for the tip on the pedal, I looked at PCMs on Kiesler and I have a couple friends nearby I think could help me out with the VAT removal, hopefully I can get a PcM from a manual and don’t have to mess with extra programming. I am planning on putting in a Miata. We IM’d a bit when you started your build, I’m only a couple hours from you.

Yeah, I get how time adds up for those final pieces, I’m pretty worried about stalling. I’m planning on completely stripping the body and repainting (mine needs it…), replacing most of the roof/body seals, then putting it back together and finishing wiring, fuel and coolant plumbing, clutch plumbing, exhaust and all the finishing minutia. I’m going to build the sub frame out completely and have most of the parts I know I need ready to go to minimize downtime, not planning to start disassembly til next October…

crxguy52

Ah that's right, I remember you now. Hard to keep track of people's real vs screen names. I'm happy to help with whatever I can since we're so close - I bought a TIG welder, so if you need something aluminum welded (poorly) happy to do so. I'm planning on modifying a generic Summit radiator ($200 vs $800 for V8R's). I'm also about to get rid of my stock front subframe - you're welcome to it if you need it to build your new subframe.

Re: PCM, from what I understand you need to buy a HPTuners credit for each PCM you want to modify. So even if you get a $75 junkyard special, you're still on the hook for the credit. That's why I'm just going with Keisler to begin with, it's a little more up front but you get something that just works out of the box. I think starting with a junkyard PCM requires more than just disabling VATS - you've got to disable a bunch of CEL codes and change some other settings as well. I'm far from an expert on this, just my $0.02.

flatpick13

I appreciate the offer, might need help with aluminum welding but planning to get a V8R subframe and probably drive lines. I have a MIG welder, but haven’t decided what I’m doing about the radiator. The guy I got the engine from already replaced the water neck with one for an RX-8, I haven’t checked to see if I have to replace it again or can work with what I’ve got.

Good call on Kiesler PCM, I was looking at that earlier today and will probably go that route. Depending on how the wiring looks when I pull the car apart I might just suck it up and buy their harness, too.

What are you planning to do for your gauges? Did you get the CANbus converter from V8R with your kit, or are you swapping out the stock cluster? Their converter is like $500, not much more to out aftermarket gauges in that already work with CANbus.

crxguy52

I misread your post, I thought you said you were building your own subframe. Your post makes a lot more sense now I considered buying Keisler's harness but it doesn't handle the fans, fuel pump, or AC compressor (if you're keeping it) - just a heads up.

For the gages I was planning on buying the CANbus converter, I just like how the factory gages look. I was going to build a CAN recorder\display for all of the other info on the bus. That being said I haven't really looked into CAN gages, did you have one you were looking at?

flatpick13

Yeah, I entertained the idea of fabricating my own subframe but would rather use V8Rs than mess with it.

Re:wiring harness, thanks for the heads up on the Kiesler harness, I’ve been re-reading gooflophaze and griffs build write ups and stress-eating thinking about wiring, the rest of the swap is a lot of work but I’m more comfortable with it, I really don’t want to get stuck on wiring…

I’d like to stick with stock gauges but $500+ seems like a lot for the CAN adapter/translator and just trying to save where I can. If I’m swapping would probably mount an AiM TFT and build a mount and face plate so it fits relatively “OEM” or replace individual gauges from somewhere like Dakota Digital and fit them in the existing bezel

crxguy52

Stress eating thinking about wiring . Honestly the engine-side wiring isn't terrible, I can help with that. Depending on how enthusiastic you get with the chassis-side wiring it can take a while, or you can just cut\terminate the unused wires and call it a day.

The AiM TFT and Dakota gages look pretty sweet, I've got a friend that went the digital dash route (chathamCNC on IG) and he seems to like it. I'm planning on just using my phone \ ipad with a bluetooth OBD2 adapter initially since it's like $20.

crxguy52

Welp, I think I may have screwed up by buying a MV7. I had assumed the MV7 and MV5 transmissions were basically interchangeable - why would there be significant differences in the "same" transmission between two cars made by the same company? This assumption turns out to have been a bad one.

It took about 4 weeks to get in touch with V8R - not the best customer service experience I've had. They finally told me that the MV7 requires a different frame rails, crossmember, and driveshaft. The MV5 driveshaft they provide uses an aluminum adapter to attach to the transmission (image below from @rdb138 ) and the MV7 driveshaft bolts directly to the transmission:



I wanted to understand what exactly drove the difference so I dove into the service manuals and parts catalogs (MV5, MV7) to try and understand the differences. I may have definitely spent entirely too much time doing this. From what I can make out, it seems like there are a few non-interchangeable parts but the important ones (input, output shafts, most of the shift stuff) are the same or at least interchangeable. The countershaft is different, but that's to be expected since the gears are fixed to the shaft and the ratios are different. The primary differences are (bottom to top) the RR transmission case, transmission extension, and the output flange:



Basically the third and fourth transmission cases from the bottom and the output flange. Obviously the output flange is an issue since it interfaces with the driveshaft, and the transmission extension (top case) is an issue because the transmission mounts are different:



That leaves the RR transmission case. I'm inclined to say these are not interchangeable - the 1-2 shift shaft isn't interchangeable, which could mean it's a different length. If I say, had a MV7 and wanted to swap over the MV5 case, I'd be worried that the bushing the 1-2 shift shaft rides in would be in the wrong spot and the shaft would either bottom our or be unsupported. Hard to tell without having both in my hands, they look pretty similar in pictures but they have different part numbers for a reason.



So, what does this all mean? I THINK if I can get my hands on the MV5 output flange and transmission extension I may be able to make this work with the MV5 kit I've got. I'll have to figure out the reverse sensor wiring and go without a transmission temperature sensor, but those are acceptable compromises.

The hard part is going to be finding the parts - you can buy the transmission extension new (~$150, 89058761) you can't buy the output flange (appears to be PN 92149642) from Chevy. A used MV5 is ~$1k, unfortunately. Anyone have a MV5 they want to part out for the sake of science?

The other option would be to just buy a MV5 and use it as-is. But where's the fun in that when I could make this way more complicated?

Update: Spoke with V8R on the phone. They stopped supporting the MV7 because they had reliability issues with 2nd and 3rd gears in their shop car and they eventually moved to the MV5. I asked about swapping the output flange and tail housing, he said the output shaft also needs to be swapped over and it ends up being more trouble than it's worth. I'm going to take their word for it and just acquire\install a MV5

rdb138

iTrader: (1)

I started putting this reply together earlier today and got busy. I was gonna try and sell you on the idea of using the MV5 vs a Franken-Transmission. Looks like Shandelle convinced you before I had a chance. Anyway, if it helps any...my thoughts on the gearing.

Note: I'm running 3.42 rear end.

From 1st to 6th gear:
MV5 4.48 / 2.58 / 1.63 / 1.19 / 1 / 0.75
MV7 4.16 / 2.51 / 1.69 / 1.27 / 1 / 0.75

1st Gear is useless (and would be useless with the MV7 too)...it's extremely short and obviously built for cars that weight a ton more than ours. Its actually hard to drive using first gear, the car wants to buck and it's almost impossible to be smooth unless you are very slow with it all. (it's great to load onto the trailer, makes it almost too easily / eager to climb up the ramps) I doubt the 3.23 rear end & MV7 together would even make this a useful gear. First being useless is the only thing that makes the entire swap feel like "a swap" in my opinion, otherwise the car feels like it came from a factory vs built in your garage.
2nd Gear these gear ratios are really close to each other. With the torque the LFX has, you won't notice a difference here. If anything it might be a win for the MV5 since you won't be using 1st gear and the MV5 is a little shorter. (2nd gear feels just like first gear in any other car I've ever driven) FYI...the MV7 and 3.23 might get you a 0-60 with no gear swap if that's something you are after. 2nd does about 55 / 56 mph at redline in my car.
3rd Gear 3rd is a longer gear in the MV5, but I don't ever feel like it's a slow gear or too long. I use it to pull out of slow corners on the track 35ish mph all the way up to 85ish and I'm never thinking the gear is too long or that I need to downshift from here. Actually, the car is faster not shifting down to second.
4th Gear Is also longer on the MV5. I think the MV7 would actually feel short here and the jump from 4th to 5th would be more noticeable in a negative way. I hit around 118 at redline in 4th before shifting up to 5th. Once into 5th, the cars acceleration feels (is) slower and you feel it more between 4th & 5th than the other gears, guessing this is due to drag just as much as gear ratio at this speed, but you would be shifting into 5th earlier with the MV7.
5th Gear same between both transmissions
6th Gear same between both transmissions

Another option to use the MV7 would be to modify the frame rails and the mount to work with the MV7. That shouldn't be that hard to fab up in my mind & sounds like the driveshaft works for you without the spacer? (or did I read that wrong?) I still think the MV5 is the easy button and I don't think you will be disappointed in the gearing.

Either way...I think you will be happy with either transmission. Good Luck!

crxguy52

Thanks for the detailed response! The more I thought about it, the more I agreed with your (and V8R's) assessment - it would be a lot of effort for not a lot of gain. I was mostly just curious if I could make it work - I've been known to "fix" things until they're broken from time to time .

The MV5 with a 3.42 rear end is actually really close to a MV7 with 3.23, I made graphs for each combination a while back for comparison. Maybe I'll go that route - would you use the 3.42 rear end if you did it again? I realize we're sort of splitting hairs here, I'm just curious. Also, what tire width are you running? Initially I'll be running the factory wheels (205/45R16) which I'm guessing will be pretty easily overpowered in 1st and probably 2nd gears either way.

rdb138

iTrader: (1)

Diff Ratio: That's a tough question. I definitely wouldn't go any higher then the 3.42. For a primarily street car / highway car, I'd go with the 3.23. For a fun weekend car / not primary and a track car...I lean towards the 3.42, but I don't know if it's best. I can say the car is a lot of fun with the 3.42, but with all the torque it has, I think it would be fun with the 3.23 too & probably depend upon the track as to which is faster.

Tires: I'm running 245/40R15 and RT660 at the moment. On a 9" and 9.5" rim (square setups, I have two sets of wheels). I plan on retiring the 9" and going 10". I think the 245 is the way to go with this car, but you could get away with a sticky 225 on a 9" rim on the street. My car grips well pulling out of corners and isn't overpowered with this setup. (It's also not too much tire, the car is still fun. Stock 1.8 engine with sticky 225's always felt like too much tire to me and lost its "fun factor", albeit it was faster on the track) Suspension setup / alignment makes a big difference in all of this. I believe you will be very quickly swapping out the factory pizza cutters :-) once you get her running.

BTW...Since we were talking about transmission. I'm not sure if you have figured out what clutch you are gonna run. I went with the atrociously heavy stock clutch and haven't had any issues. Seems like all the guys that went with a light aftermarket clutch had a lot of issues. You may want to ask around about that more. (Someone might have fixed the issue by now)

crxguy52

It'll mostly be a fun\weekend\occasional track car, so 3.42 it is. If you feel like it's balanced with 245s then that's what I'm shooting for - I don't want a drift machine, but I do want to have to actually think before mashing the gas. On my NSX the gearing is way too long (2nd tops out at like 80) and it takes some of the fun out of driving it. On the other hand, I had an S2k and it felt like I was just shifting constantly - I'd usually end up in 6th by 35mph, no joke. Somewhere in the middle would be nice. Totally get what you mean by "fun factor". I tracked a CRX pretty extensively (hence the username) and while it was fun to drive, throttle application didn't require a ton of finesse.

Re: clutch, I read the horror stories from the other build threads, I plan to just stick with the (heavy) stock setup. Pulling the trans in this car seems... challenging at best, and I want to minimize the number of times I've got to do it. As much as I like a light flywheel, I hate pulling the drivetrain more.

crxguy52

Mounted the drive by wire gas pedal over the past few weeks, I took a slightly different approach than others since I'll be reinstalling the carpet. Take it easy on my fab skills, this is my first metal fab project in probably 15 years . I started with a reference photo to compare the completed product to:



Stock throttle bracketry was trimmed off - in hindsight I would have left the vertical part on the right side intact, it'll become more obvious why later.



I traced the throttle outline and mounting points onto some paperboard, then transferred the pattern to 0.060" mild steel. Using my newly-acquired I-beam I bent stiffening tabs into the bracket. These ended up working out well, the top tab lined up with the factory pedal assembly and made for a much stiffer attachment. The I-beam was cheap and made this job so much easier- if nothing else it was a heavy thing to clamp the workpiece to. Highly recommend.



Bracket was tacked onto the assembly at the top and test fitted. Based on other build threads I was expecting this to be a formality, but I found two issue: the bottom mounting tab was touching the transmission tunnel and the pedal was too low - enough so that with the carpet installed I might not have been able to reach full throttle.



There wasn't a ton of room to move it left or right, so the only option was to space the bottom up. 10mm felt about right and left sufficient clearance on both fronts



I wanted to make sure the throttle was mounted securely - I wouldn't be surprised if the pedal saw significant force from the nut behind the wheel. The slight angle made mounting more challenging, I was expecting to just lap welding the bracket on. I cut out two stiffening braces and welded them in , one along the bottom of the pedal and one running vertically. Since stiffness increases with the cube of the height this worked out to be a nice stiff mount.



I opted to tack some bolts in at the top to act as mounting studs. I could have used studs for all 3 mounting locations but I think they're kind of ugly, so I used a nut for the bottom mount (there was no space for the top 2 locations). I gave it a quick coat of paint and called it a day second weekend





And here's a reference photo in case someone wants to get the bracket laser cut.

Z_WAAAAAZ

Not bad for your first metalworking project in 15 years! Comparing the two, it looks like the lower part of the accelerator pedal will be a hair closer to the brake pedal than the original setup. Might help out with heel-toe'ing as well!