Firewall gage

What gage does NHRA require a modified firewall to be?

mild steel .024 or 24 guage

Yep. .032 if you use aluminum.

Thank you,

Are you changing the firewall Josh? The stock one has plenty of room, unless you're setting the engine back & need more clearance. Mine is set back about 1-1/2 - 2" from the stock location with the foxbody set-up, and I can still get my valve covers off without too many problems.








Doug...

There is pleanty of room as my engine sits 1 to 1-1/2" further back than stock also. I was going to try to cut out a majority of the factory holes and dings in the firewall. Where the transmission tunel and firewall meet it looks like someone beat the edge in with a large hammer. I was thinking about cutting that entire edge out and patching. Looking at the picture the worse area is on the lower right edge, before it turns to the transmission tunnel. I tried beating it back out from the inside but I'm not the best body man.

bruno wrote:mild steel .024 or 24 guage

Actually using basic mild steel sheetmetal sold/advertised as "24 gage" might be too thin to pass the .024" minimum depending a number of factors.

Always double check the actual thickness when buying sheetmetal sold by the advertised "gage thickness" (vs decimal thickness) because industry standards always allow some fudge room. The sheetmetal advertised gage thickness can be thinner than the expected actual decimal thickness sometimes.

And technically if we are being 100% accurate, 24 gage should be too thin anyway since a lot of charts say for mild steel sheetmetal 24 = .0239" thick. I usually choose between either 22, 23, or 24 gage just to be safe and measure to see which gage in stock is the closes match that day. Sometimes any given batch of sheetmetal can be way off on the actual thickness, it's just one of those things that needs to be checked.