Here come my Twins!
 

I'm returning from deployment in a few weeks and then shortly after I'm dropping the camaro off at GPI. My current mods are in my signature and this is what I'm deciding to add:

-Twin 58/62mm Ballb Turbos from AGP
Fuel to support 900-1k+ (not positive what setup yet)
-Built 4l80e swap - imagine I'll have to be lower than a 4k stall
-Forged pistons/rods, leaving everything else stock on the L99 besides what's in my sig.
Replacing the SS4VVT with a custom ground turbo cam from GPI
And going with a 15" conversion in the rear to run 325/50/15 ET Street Rs

That's about all my budget can fit, I'm concerned about the rear end and that's about it. What are your thoughts? I plan to be around the 900whp range, we'll see what it makes. I'm more concerned with running 9s and getting as deep as I can into them! While still having the ability to do rolls.

I'm leaving the 3.91 gears that I have now, I think it will actually be a pretty good combo with the built 4l80e. I'll still be able to reach 155mph or so. Let me know what you guys think, like I said my main concern is the rear end, but I won't be launching it that much tbh, until I can afford to build it!

Maybe a 2 step or a trans brake to build boost off the line, that will be harder on the rear though. Going to be a fast car

Yea dude, that is going to be nasty, I would consider the ZL1 diff from the start since you will need a custom driveshaft for the 4l80 swap anyways. Of course get proper Drag suspension so she sits up right off the line!

Good Luck man... keep us up to date!

GPI will do you right! Can't wait to see the results...

The staff there are top notch...

GPI is building my forged SC motor, that will be exciting!

Most importantly- thank you for your service....

-Don

I preach planting the power before producing the power. I don't practice what I preach. So, I will soapbox my hypocrisy and say - do a suspension drag package along with a stronger differential. I do not believe a built-up stock diff will live long. Most economical diff is a ZL1, and the 3.73 will be more than tall enough. I think the 3.91 will show you more tire spin than you'll be happy with, and you'll even get more tire spin in the higher RPMs rowing through second and third gears with the 3.73. Just saying. Back to the suspension - something like stronger trailing arms and toe rods at minimum. And, with the 15" conversion you'll need different lower control arms. Fast is beautiful.

Totally forgot to mention I will also be trying to squeeze a trans brake and two step into the build as well, as it will be essential to get those solid ass launches! Slipped my mind when writing the post though, thanks for the reminder!

Yeah that's a good point, I do have some suspension right now, but will have to swap my BMR trailing arms/toe rods to the 15" conversion ones from Carlyle! I'll look into the cost of swapping diffs! Thanks much ���� I will definitely be posting back when the car is done sometime in August hopefully, I'm super excited! Can't wait ha.

Yeah GPI has been good to me, went there for my first big step into the build when I went; their heads, SS4VVT, their radius rod insert and a few other mods. Amazing staff, amazing work they do. I will never take the car anywhere else! My car pulls like a train already for what it is.

And no problem my friend, I enjoy what I do; for the greatest country on earth ����

Yeah I have some suspension right now, my BMR trods and trailing arms will get swapped though with Carlyles 15" kit. I figured with preventing wheel hop and a 325/50/15 ET Street R I would be pretty good for traction honestly, and be able to hold the 3.91 gears off the line haha. I do have the BMR lower control arms as if right now as well, I'll see what else GPI recommends! Thank you!

I'm doing a similar setup and went with a 3.73 zl1 diff. The stock diff should last at 900 and a auto. I've been waiting on sps haymaker heads for almost three months now.
Twin billet s261
4l80 rpm lvl5
Sdpc iron 365
Lil John custom cam
Id 1700s, twin 450s, meth blah blah blah

Sweet build!
I have a similar build
TH400 3500 stall
Built 6.0 iron block
Twin agp 65's
Agp twin walbro 450's
Allky control meth system

I would highly recommend a transbrake and 3.45 gears, turbos love load. Also I would recommend meth, nice way to prevent detonation if you're not going with E85.

Good luck!

Yeah that sounds nasty too! I'm about 500whp NA with my 6l80e. I figured adding efficient boost, fuel to support it, internals and a 4l80e I could make about 900 and be fine tbh. Hope it works out for you too my friend! I'll post back here in about a month when I drop my car off and then another month when it's done!!

Similar but I'm still looking to do rolls which is why I didn't go with the TH400. I'm not sure what my new stall speed will be at, I'm currently running a 4k 5c triple disc converter from Circle D. I'm just going with internals on my L99 and I think that's enough haha, not positive though. Yeah a trans brake and two step will definitely be necessary, my budget is just about out though haha. I'll find a way to squeeze them out. Meth is definitely an option, I'll have to see what Ryan at GPI recommends, because I'm probably staying with pump gas. As for the gears, idk, I really want to stay with 3.91. I think I have a setup that can handle it from a dig and from a 40-50-60 roll it's going to be a train!

I'm not the expert though and I trust GPI, I will just see what they think is the most optimal setup! I'll read more into it though, people seem to keep saying go 3.45 or 3.73!

Your gonna love it. Id recommend a fuel system from agp. I just installed a dual pump e85 setup from them and am very happy with it. I would suggest putting that 15" conversion part of the budget towards a zl1 diff. Otherwise it will be a matter of time before a stock unit goes especially with 15" fatties. Go with some 17" for now until you do the 15"s.

EDIT: Just saw youll mainly be doing rolls so you should have better luck with that stock unit but I wouldnt stick too much into it. Ive learned the hard way to do it right the first time.