Wood firewall question

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Model T Ford Forum: Forum 2012: Wood firewall question
Top of pagePrevious messageNext messageBottom of page Link to this message  By michael grady on Monday, June 25, 2012 - 08:28 pm:

Hi Guys,

I'm trying to replace the torn up wood firewall for my 16 touring. I have some very nice 3/4" Cherry plywood that I'd like to use and just copy the old one. However the fit into the hood former is just a little too tight. A couple of questions...

Is it usually necessary to bend out the tab that forms the slot that the wood would slide into, i.e. enlarge the opening so the wood fits, or are you guys just reducing the thickness of the plywood?

Also, do you put any kind of caulk between the hood former and the wood?

Thanks,

Michael


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Mays on Friday, June 29, 2012 - 05:05 pm:

Michael, I just replaced the firewall in a '15 and I used a wood rasp to "narrow" the edges of the firewall so it would fit into the hood former. I was reluctant to bend the hood former edges. It took a little while to do that but I think that is a better way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Dupree on Friday, June 29, 2012 - 05:16 pm:

When I replaced the firewall in our '16, I made sure the firewall was stained and clearcoated (I used automotive polyurethane) on all surfaces before installation. Like John, I used a rasp or sander to taper the edge just a little to get an easier fit.

Ron Dupree


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Johnson on Friday, June 29, 2012 - 06:41 pm:

You should contact John Regan - he has studied the firewall blue-prints and reproduced correct firewalls in the past. He can tell you the correct thickness for 1915.

I believe that for early 1915 Fords the firewall was 3/4" but had a 1/16" rabbet around the edge to accommodate the hood former but the design was later simplified so the entire firewall was 11/16" thick.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Friday, June 29, 2012 - 06:50 pm:

Erik has is correct. The firewall nominal thickness was 3/4" for dashes until early 1915 when it changed to 11/16 where it remained through 1923 and the end of wood dashes in early 1923. You will screw up your hood former trying to put it on a 3/4" thick piece of plywood. The hood former for 15/16 is set up for 11/16 thick material and as Erik stated, they used a rabbet around the edge to then fit the former to that 3/4" nominal thickness dash used only in early 1915. The 15/16 edge is a complicated form with a taper on the edge and then 2 different radius on front and rear edges to make up the edge that then fits snug inside the hood former. It also includes the rabbet if the dash is an early one. Since I make show dashes I finally popped for a custom router bit just for 15/16 dash edge. The taper is a weird angle and not available off the shelf on any standard taper cut router bit.

I would not use just any plywood for a dash since typical cherry veneer plywood has soft core ply and will crush easily when you tighten up your steering column bolts. They will then quickly loosen up again. Use appleply or baltic birtch type plywood. The correct face veneer for 1915 and later is hard maple and not cherry.


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