Tim's has a 8.8 from a Thunderbird IRS.

 

The CTS diff problem was addressed by GM at the end of '06. There was a pinion seal leak and the seal has been redesigned as has the case.

My diff was easy to get. This car won't be a dragstripper, so I'm not worried about blowing it.

Frank

 

I received the exact same reaction to the CTS diff from some knowledgeable folks here in KC (shop owning, American muscle, drag racing types). The Ford 8.8 IRS was universally recommended.

Are you guys counting on the Miata to be easier on diffs because its such a light weight car?

 

I'm counting on it being better on diffs as the '07+ diffs aren't experiencing the problem of the < '07s. Wheel hop might be a cause too but I'm assuming I'll see much more wheelspin than wheelhop. Plus the V8roadster kit has more solid mount for the front.

There were a lot of complaints of the T-bird 7.5 rear in Fords but no problems when they're put in Monster Miatas.

Frank

 

Wow how did I miss this thread??

Personally I think 4k is a bit extreme for a swap kit, but theres plenty of people who will pay it. If it actually came with some nice longtube big primary (1 7/8") headers then I think 4k would be well justified.

For anyone who saw my LS1 FD RX7 drive thread.. They spend around 14k total on a car and sell them for 20 - $30,000 without any lax in orders. Come on, bone stock motor you're running like 11s or low 12s, 30+mpg highway driving, and can out accelerate 98% of Hondas in sixth gear..

Seriously though, LSx's respond VERY VERY well to even the simple mods. Heads/Cam/intake/longtubes and good program will easily pickup over 100 horsepower. As for the GM Computers, yeah, 100% programmable with LS1Edit and its not even that hard to do. Get real wiley and strap a P1SC @ 8psi intercooled onto it and expect to never get traction again. Ever. It'd be a dyno queen, like Supras.

Good luck on the kits, Keith. I can tell you, if you build it.. They will sell.

 

Supply and demand is why the kit costs so much. The FD guys have cheaper kits because there are more guys taking on the swap. I will say this again, the kit is a perfect fit and really well done. The Racing Concepts kit is cheaper but there are a few things I didn't like when shopping so I went V8roadsters.

Frank

 

nvm..

 

group buy...

 

They just need to say when and how much. I'll buy everything minus the rear end kit, which will be Racing Concepts 8.8 kit which uses an explorer aluminum diff

 

You'll need a custom driveshaft. The v8roadster kit sits the motor back further than the RC kit. So if you're doing the RC rear, they'd need to cut the shaft shorter for you.

Frank

 

Thank you for the heads up! How much lower does the v8roadster kit set the engine?

 

It sets it back further, but I don't think it is any lower. It would be hard to tell without both cars next to each other.

Frank

 

do you still have to cut a good portion of the tunnel out? looked like the tunnel had a decent amount cut out of it with the v8roadster kit.

 

Zenspeed also has a kit coming out sometime which is supposed to allow you to run any header you want because they pull the steering shaft out of the way.

 

You don't really cut much out. You do cut it (maybe heat it) and bend it in then weld it up for more clearance. Same difference I guess. I've done most of the cutting, and my welder should arrive tomorrow.

Zenspeed has been promising a kit for a year now, but still offers nothing. A reason I like the v8roadsters kit is it keeps the steering geometry, which avoids bump steer which I read was an issue with the original RC kit.

Unfortunately, the headers from v8roadsters has been delayed. The mandrel bender the were getting them from didn't deliver as promised.

Frank

 

What about the strength of v8's subframe vs. OE? From photos it doesn't seem that it could be as strong since there's so much less of it, but I'm not a structural engineer. I'd like to here HOW it equals or exceeds the OE subframe strength. I suppose you'd want it to exceed since it's a power upgrade. That subframe is ideal for a lot of different swaps- but at that price it's probably out of reach for most budget swappers.

 

hey frank, you know my welder made it "home" almost too. scott has it at his place (couple miles up the road)

but since you'll have one... and I might find some time in the next couple weeks...

 

Can you shoot some pictures of the area you cut up? I've really been back and fourth between RC and V8roadsters. What is V8roadsters new deadline for a header and what size header tubes will be used? I'd hate to choke up a built 347 with a 1 5/8's inch header.

 

I have a slightly more detailed writeup with some pics at:

http://forum.miata.net/vb/showthread.php?t=278524

You can see the pic where I cut the ears off. That area below the cutoff ears still needs to be widened to 18 inches across and down about 6 inches on both sides. I've done most of it but need to make another small cut because there is part of a support right behind where I'm cutting in the NB. I don't think the NA has it.


If you PM me your email, I can forward you my pics of the modifications that I have done to the tranny tunnel, plus where Shandelle from v8roadsters showed me I have to make it a bit wider.

As for the strength of the subframe, I guess time will tell.


Frank

 

Shandelle said he'd be doing the headers by hand until they find another header fabricator that can do it for them. Part of the problem is probably the limited amount of buyers.

Maybe the RC kit headers will work? Dunno.

The v8roadster headers have a 3 inch outlet but I'm not sure the size of the runners.

Frank