Twin turbo mullet build

[GTA matt]

I'm bored, and I should probably be working on this thing right now, but here we are... I dragged this 89 iroc home a little over 2 years ago, fairly stock 305/t5 car. I really just wanted a nice street car, drive anywhere, maybe do some occasional drag racing and autocross. Really had no direction, other than to just do whatever I felt like. Within the first few weeks of owning it, I replaced the rear with a 9", added some suspension stuff, put wilwood brakes on all 4 corners, a t56 magnum trans, and built a nice 383 for it.







Rear end is a burkhart chassis chromoly fab 9, I built a strange iron center, have put a couple sets of gears in it, currently 3.25's, strange 31 spline axles, eaton true trac diff. I have an aluminum center with 4.10's and mark williams 40 spline axles that I can swap in for drag racing.





Engine is a 4 bolt main gm block, eagle forged crank, rods and mahle pistons. Compression works out to 10.92:1. Cylinder heads are afr 195's, comp xfi292 cam, tpis miniram intake manifold. Put an efi connection 24x crank reluctor/ timing cover/ cam sensor on it so I could run an LS based ecm and coils. Wound up using a fitech ultimate LS computer. Ran the engine for a year and a half, 10,000 miles, in this configuration with zero issues. Estimate it was making in the low-mid 500 hp range. Exhaust was 1 3/4 headers, to a 4" single mufflex exhaust.

[GTA matt]

The car ran pretty flawless in that configuration. I never made it to the drag strip, but I was able to run some autocross events, where the car performed excellent. When I originally built the engine, I had in my head that I would most likely be putting a procharger on it, which was the reason for the forged bottom end. As it turns out, peer pressure is a bitch, and I wound up getting talked into going the turbo route, I knew I still wanted to drive the car anywhere, have full exhaust, and also wanted to keep AC. Looking at what some others had done, with turbo placement and hotside routing, I figured there would be little room for the headers, crossover, and a 4" downpipe with all the factory AC stuff in place. That's when I decided to go with twins, as dual 3 inch downpipes were totally doable. I didn't go twins for any sort of power advantage at all, in fact, I'm pretty well limited to what the stock block can hold. I'll most likely put together a dart block for it in the future, but this should do for now. I did it more for packaging reasons, plus, it looks pretty awesome. Originally, I intended to build my own headers, downpipes and cold side, but while googling pictures to get some ideas, I ran across cx racings twin setup. I probably couldn't build something as nice, or for less money, so I'm giving it a shot, along with a pair of billet wheel vs racing 61/62 turbos and vs 44mm wastegates. Headers and intercooler fit well, but I had to mod the hell out of the downpipes to fit. In wanting to keep the ac, the factory belt setup simply would not work, so I installed an Eddie Motorsports s drive setup. Pretty compact, with modern compressor, water pump and power steering pump. I also pulled the engine, opened up the ring gap a bit, and installed a slightly thicker head gasket to drop compression to 10.5. I'll also be running meth injection, since I know compression is a little sporty. I will not be running e85, mostly due to the fact that I drive it too much to be able to consistently find e85 stations. I don't want to plan a road trip around fuel stops. Inside of the engine was perfect when I had it apart.



This is how it currently sits. Nearly complete, a few odds and ends on the topside left to go. On the bottom, i'm building the downpipes out of 3" stainless, leading to the existing 4" exhaust. It's not as easy working in a 3rd gen engine bay, and all problems and parts are multiplied x2. The drivers downpipe is about done, leading under the oil pan in the factory routing. Passenger side is half done. This is my first time tig welding stainless, it's a learning curve... The wastegate pipes are going up and out the hood vents, because reasons.













I also upgraged the wheels to a set of 18x11 rotiform 917s. Wanted something clean and simple.





Still have some work left, finish up the exhaust, lots of heat protection, move the fuel lines, install new fuel pump, and any other little problems that pop up... Hopefully will be up and running soon

[98s-281]

Nice looking IROC.

[theheder]

I like it!

[The Flying Clutchman]

Totally rad

[Hotwire]

Great job man!! Sure you're knockin eagle feathers out of the mullet with it setup like that!!

[Tubbed440]

That's sweet! Nice work man!

[jcsperson]

[rcktpwrd]

real nice!

[blazinbowtie99]

I have a boner. Nice ride!

[TTSALEEN]

That is awesome! You are making HPJ great again! Rock on!

[Blue70]

Daaaaaamn!!

[Russell]

Very Nice! Are you keeping the Fitech?

[GTA matt]

Originally Posted by Russell

Very Nice! Are you keeping the Fitech?

I am for now. It's...ok. It runs great, never had an issue as far as that goes, or even tuning for that matter, has tables to support up to 20 pounds of boost. But datalogging and the interface between the laptop and software is frustrating at times.

[GTA matt]

Got some more work done to this thing. Finished up the passenger down pipe, the y-pipe and made some support brackets for the down pipes, coming off the cylinder heads on both sides up top, and using the bellhousing at the bottom. I'm trying my best to keep everything easily removeable for service, as the upper part of the downpipes has to be removed in order to get to the spark plugs, which is the reason for all the multi-piece support brackets. I had originally planned on doing v-bands in front of the y-pipe, so the rear part of the exhaust could be easily separated, but there simply is no room for them. Instead I opted for some nice band clamps that could be simply slid off.

[Tubbed440]

Tight squeeze in there! Nice work man!

[rcktpwrd]

WOW

very nice looking work there!

[GTA matt]

I may have gotten carried away with the exhaust... I began building the exhaust from the y-pipe to the existing mid pipe. Ground clearance with the 4" pipe was limited, I've scraped over speed bumps, so I wanted to get the exhaust tucked up as high as possible. Also for ease of disassembly, I didn't want the y-pipe and mid pipe all one piece. Soooo I made a bunch of pie cuts and got the exhaust tucked up against the floor in the factory cat location with a v-band clamp. The exhaust is pretty much 100% done. I still have 2 welds on the pipe left and need to make some hangers, but I ran out of argon in my backpurge tank. Also got some more things buttoned up, starter cable, cleaned up some wiring and made a heat shield for the starter. I'm not sure if I'm going overboard on all the heat protection or not, but I've burned up my fair share of crap in the past, not taking any chances here while it's all apart...

Starter heat shield and strategically placed upper downpipe v-band













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[rcktpwrd]

Looks great!
That was a ton of work to gain a bit of clearance! Should also look cleaner from the side of the car not seeing the pipe hanging down...

[GTA matt]

Originally Posted by rcktpwrd

Looks great!
That was a ton of work to gain a bit of clearance! Should also look cleaner from the side of the car not seeing the pipe hanging down...

Holy cow it's an insane amount of work. I don't really have the right equipment to be making pie cuts out of 4" stainless, there's several hours just getting those things made. And I do know it took exactly 41 minutes to weld the pipe in the picture from the welding table. All for stuff that will never be seen...

[Tubbed440]

Originally Posted by GTA matt

All for stuff that will never be seen...

But you know it's there, and that's what counts.

[Mwilson]

wow very nice

[Snowman]

Excited to see this car on the road for sure!

[GTA matt]

Oh yeah, forgot about this thread. Car is done. Thing freakin rips, absolute blast to drive. Turbos spool immediately, Its making 6.5 lbs of boost currently, which is perfect for getting a handle on tuning. First 3 gears are useless anyhow so I haven't bothered trying to turn it up.

[rcktpwrd]

looks great!

I bet it's a handful!