Need help with firewall clearance with a 14-71

I don't have a blower to mock up for my door car and I need to know how wide to make the box in the firewall in order to clear the blower. I have the setback figured out and from some blueprints I've seen, a 14-71 case is about 12" wide. Any feedback is appreciated!

 

http://www.darkside.ca/images/blower-images/open.jpg

 

I will tonight when I get home. Most people forget about the bag. I made mine and had car powder coated before I had the blower. After I had the blower I had to remake the blower box.

 

That's exactly what I'm trying to avoid! Thanks!

 

My Haas car has a slot that is 15 3/4" wide by 9 3/4" back and 6" high at the firewall. I had a SSI 14-71 at one point and had ample room around the bag with this setup. Hope this helps.

 

Thanks, that will help. With my car we will go all the way back to the dash bar , and based on your info, if I make it 16" wide I should be good for blower and blanket

 

His Bickel car is almost identical to what I did. Hope that helps