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Old 07-26-2016, 02:27 AM   #1
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Default Removing FM frame rails -- NASA TT

I was stupid and bought a chassis with FM frame rails. I thought I would never use my track car for TT or W2W but am considering it now that I have a cage, so the rails need to go. I now have 24 5/16" holes in my floor.

Before I get deeper in asking around, does anyone have a more educated opinion about what legal ways there are to close these holes? Can I have steel patches of equal thickness to the OEM floor welded in? I couldn't find any info about "repair" techniques in the rule book outside of the E46 allowances.
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Old 07-26-2016, 11:55 AM   #2
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Personally, I'd run with the frame rails unless you absolutely need the points back. They're worthless for stiffening, but are great skid plates. Have them on all my track cars for that reason.
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Old 07-26-2016, 12:43 PM   #3
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Metal duct tape
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Old 07-26-2016, 02:06 PM   #4
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Originally Posted by hornetball View Post
Personally, I'd run with the frame rails unless you absolutely need the points back.
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Metal duct tape
These are basically Step 1 (keep them while I work on driver mods) and Step 2 (Home Depot Motorsports) for me. So would anything more permanent like welding holes shut be suspicious?

I guess the passenger-side ones make nice ballast and cool suit mounts.
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Old 07-26-2016, 02:09 PM   #5
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Is there any real need to weld them shut? They're small holes so they don't hurt stiffness much, especially with a cage in the car. Metal duct tape (the kind you actually use for ducts, not the gray fabric kind that's used for everything else) will seal them against water or exhaust or whatever getting in the car, and if it's a race car you're presumably not hugely concerned with aesthetics of the underside, so... why?

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Old 07-26-2016, 02:11 PM   #6
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No one will care if you weld the holes shut. Harbor freight welding spoon on the underside, fill with weld, hit with tiger paw/flap disc, paint.
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Old 07-26-2016, 03:37 PM   #7
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We have filled large, non-structurally sensitive holes in the tub by riveting small sheets of aluminum over them and sealing with silicone.
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Old 07-26-2016, 05:04 PM   #8
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Is there any real need to weld them shut? They're small holes so they don't hurt stiffness much, especially with a cage in the car. Metal duct tape (the kind you actually use for ducts, not the gray fabric kind that's used for everything else) will seal them against water or exhaust or whatever getting in the car, and if it's a race car you're presumably not hugely concerned with aesthetics of the underside, so... why?

--Ian
Fair enough, I can certainly just live with the speed holes
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Old 07-26-2016, 05:08 PM   #9
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Thanks all, looks like I have lots of options and it's really no big deal starting with tape. Was worried it wouldn't hold up, but now that I think about it that aluminum duct tape is tenacious.

I'm trying to get as much of "the car I want to build" without throwing points away, so taking the frame rails off is a no brainer to use the 6-speed I already own.

Time for me to take this to a build thread -- as soon as the freight carrier gets their thumb out of their *** with my VVT engine.
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Old 07-27-2016, 11:04 AM   #10
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I've been shopping around for VVT engines, where did you pick your up if you don't mind me asking?
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Old 07-27-2016, 11:26 AM   #11
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ebay is actually a good source. If you can find a JDM engine, it's an extra half point compression (10.5:1), TB mass damper and square top. EU and the rest of the world get the square top but no mass damper and the same 10.0:1 as USDM.
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Old 07-27-2016, 11:44 AM   #12
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ebay is actually a good source. If you can find a JDM engine, it's an extra half point compression (10.5:1), TB mass damper and square top. EU and the rest of the world get the square top but no mass damper and the same 10.0:1 as USDM.
Awesome, that's some great information I hadn't come across yet. I really appreciate it.
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Old 07-27-2016, 12:08 PM   #13
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Quote:
Originally Posted by emilio700 View Post
ebay is actually a good source. If you can find a JDM engine, it's an extra half point compression (10.5:1), TB mass damper and square top. EU and the rest of the world get the square top but no mass damper and the same 10.0:1 as USDM.
Exactly this. I got a complete, low-miles (with looks and compression tests to back that up) JDM BP6D on Ebay for a great price. It came with the squaretop, TB damper, all accessories, and a 6-speed.

Still got the Skunk2 TB to put on it because I have no idea how safe I would be with the mass damper.
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