Frame inside cab - legal?
 

Really odd question. I'm looking to do a channeled, altered wheel base 80's square body. The best way I can see to get what I'm after is to run the frame members inside the cab, along the rockers. The firewall and rear wall would be flanged and welded to to the frame (probably 2x3 or 3x3 tube) and a roll cage added (which is actually what drove me to this idea). I want the truck to have working heat, etc, which is why I'd like to keep the existing firewall, as all those little bits are already mounted up.

When I read the (apparently deliberately) confusing IRHA ruelbook, there is almost nothing in it for ET brackets, specifically for vehicles that don't fit neatly into one of their classes. Which is where something like this would have to run since the engine is under 300 cubes.

Side note - IHRA because the just reopened Onondaga dragway here in Michigan, and since the noise from that is what got me into cars, I'd liek to pay it a visit with something the Michigan Madman (EJ POtter) would ahve appreciated.

Sooo... does this count as a firewall modification? Because if I read it right modified firewalls require a whole bunch more stuff and I'll just run it on the street. Kind of funny because I can run rotted rockers and floors patched with scrap road signs, cover it with carpet and apparently pass tech.

Re: Frame inside cab - legal?
 

So it depends on how fast you want to go. 300 cubic inches does not matter.
Jimmy

Re: Frame inside cab - legal?
 

What's all this? Are you keeping secrets from me?

;)

1/8th or 1/4 mile?

If it's 1/8th mile I don't think the vehicle speeds will put you in a range where you need a lot of protection. I also think you will find these smaller local tracks (like Lapeer "International" Dragway) are much more liberal with their safety inspections than their major counterparts.

(Actual Audio: "....Zat yer helmet?" Yep. "You got shoe polish?" Yep. "Yer good to go.")

In either case I don't think that counts as a firewall change. The firewall change is intended for full tube frame cars where the original body sheetmetal is fitted over the rolling chassis/roll cage structure, with the original firewall being completely removed. Also - for cars with removeable trans tunnels (for transmission maintence and removal) it drives an additional crosscar bar below the dash in the roll cage.

Almost everything I do is through NHRA, but they have dedicated inspectors by region that you can consult. If there is a name in the IHRA rulebook it would be prudent to run your plans past him before you get too far.

K

Re: Frame inside cab - legal?
 

300CID matters because a 3800# truck with an overbored 292 is still slow.

Keith, it seems that I have a 2 ton cab with small back window and flat floor just sitting in the back yard.... The small window leaves room for the rear down bars... and I think a little imaginative cutting would allow a roll bar to be put in the rear pillars and run just inside the front pillars. Would make a really rigid chassis with minimal interior impact, allow the truck to be dropped (IHRA says 2" min ground clearance - but that won't go across my yard) and eliminate the need for offset roll bar to frame braces.

Looking at my collection and starting to think of 'use it or lose it'. And retirement is coming up on the horizon.

Re: Frame inside cab - legal?
 

I have the area under the pedals modified, its actually kicked out 5.5", sloping from the floorpan up towards the main body seam at the firewall. So far, every place I've been has agreed its a mod to the floor, so the firewall rules didn't apply. My guess is they would treat you pretty much the same.

I see the firewall-specific rules for cages etc coming into play with things like the Stretchy Truck, which is rear engine and thus needed a rear bulkhead/firewall. Or AF/x cars where the firewall has been moved like 8".