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S550 Verus Diffuser install on GT350

Ok so I got around to doing the install myself and with about 90% typical hand tools it can be done. The diffuser really does need some modifications for the GT350 and if you have the skill set I say take your time. If you dont then it is well worth it to pay someone that can handle the task. My time took about 9 hours total and that was due to trial and error on my part. Another thing that came up is if you have the grimm speed exhaust valve simulator then this diffuser will need a new rear bracket manufactured with a welded on bolt. The rear hangers dont really work unless you cut the honey comb on the GT350 bumper so you can put a wrench on it.

Ill try my best to describe this process
1) I cut about 4 inches off of the strakes ( front portion) of the stock ducts
2) Centered it and took a paint pen and drew it on the diffuser, Second pic with paint was an idea I have for my vents and after I made my cuts I kind of wish I had went with the oval cutout.
3) Drilled out with a #30 (1/8") drill bit.
4) Drilled out to 1/4" since the stock part had larger holes from the factory rivets.
5) Taped up the diffuser so I could lay out a pattern.
6) As you can see in my pattens I wrote measurements but 4" in the front was a but too wide so I would start at 3". I lost one mount on the inside portion of the stock part.
7) I had a small hole saw and a 16 MM socket had the same radius so I decided to make a radius on it. I don't think its necessary and you could get away with hard angles.
8) Cleaned up all the edges and deburred all the new holes.
9) Added some heat shield like @Black Boss because it is very closet to the mufflers and it can't hurt.

So the install for the front and side mounts is very straight forward. The rear hangers will hit your rubber exhaust mount and are too short for the GT350. I took a paint pen and set it in the factory tabs and picked up those holes. BUT I broke one. Therefore, I have to get clever because I wanted to complete this. I took some spacers and added it to the rear Verus mounts (be careful they do have a left and right side but they are not marked). Then I had to elongate the Verus hole mounts. Then I have to buy some longer hardware and I used hex head bolts. Next I cut a small opening in the honeycomb so I could get a 10 MM wrench in there and hold it tight. Once I had everything loosely mounted I was content and worked on leveling the diffuser and tightening the hardware.

I will make a proper rear bracket but that will be in due time. Till then I just wont do any track days that the GT350 can't pass sound or I will install the remote exhaust valve simulators, But in the end I do want it to be a piece that can be removed and installed easier.

AND FYI I will not do this again. Its a real PITA due to the rear mounts.

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@byronj As an alternative to making a new rear bracket, I used screws under the reverse light (for location only, not strong enough as a primary mount) and then the diagonal braces that the OE diffuser uses and the exhaust mounts. Only the reverse light needed spacers (about 1/2”). Rough dimensions below. Longitudinal measurements are from reverse light holes (which have narrower spacing on 350):
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2,023
818
Bay Area
So a few other items I noticed or figured out, I did use the reverse light mounts that @Black Boss pointed out. One thing I will say is DO NOT be afraid to elongate the mounting points. The easiest way to do this is find the center and drill with a small bit to create a pilot hole, then drill out with a 1/4“ bit. Take a dremel or small file and clean it up.

Also, since I cut out the small area of honeycomb on the rear valance, I was thinking I might cut it all out for ease of access and I can install a small spacer since I decided to use the Verus mounts.
 
Great write-up Byron! I did a few things differently so I thought I'd chime in to help some people out too. I modified the original diffuser to transfer over the front portion of it as well and I also wanted to keep the full length of the strakes rather than cut them out. I didn't measure anything with a ruler or measuring tape or cut out the rear honeycomb. Here's what I did.

1) Removed the original diffuser and separated the cooler ducts from the rest of the assembly.
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2) Then I used the the original diffuser as a template and laid it on top of the Verus one. Then I lined up the rear most mounting holes with each other which allowed me to see exactly where I need to put the cooler ducts and trace the necessary lines.
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3) Once the main holes were cut out. I widened the front part of it a little more to allow the entire cooling duct assembly to "pass" through so I didn't need to cut off the front 4 inches like some other people did.
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4) Riveted the cooling ducts to the Verus diffuser and then riveted the front portion of the stock diffuser to make my complete, Frankenstein assembly.
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5) The front "y" brackets needed some "massaging" to line up properly (a few good hits with a rubber mallet) but it all bolted up nice and sturdy. The 2 rear-center mounts were a pain in the ass in the beginning just like Byron mentioned. Instead of cutting out the honeycomb to get the nut on the top side, I installed a couple clip-nuts just like they were on the brackets for the stock diffuser. I had to bend the brackets a bit to get them to line up but it all worked out perfectly in the end.
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Still enough clearance to get in and out of my driveway!
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My daily-driver in the background. Gotta love those peppy little ZX2's!
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2,023
818
Bay Area
Nice job Jesse. I wish I would have thought about the clips. Now I’ll have to get new panels and put clips in there. It hey it’s learning lesson. I can’t get out of my driveway . I have to put a 2x10 on top of my bridjit / steel plate extension to clear. Gotta love the steep drive aprons in the Bay Area.
 
1
3
Exp. Type
HPDE
Exp. Level
5-10 Years
Asheville, NC
Just wanted to say a BIG THANK YOU to everyone that contributed to this thread. I just used this for the installation on my 2020 GT350. I was at a loss when I looked under it and found that factory diffuser. Mounting points are a little different toward the rear of the car but none the less same installation.
 

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