20 small holes or 1 big hole?

[MiraclePieCo]

When I bought my truck I was thinking, "Great, someone already filled the firewall." Yeah, with bondo. I spent the day knocking out the bondo plugs with a hammer (yes, including the 4" heater motor hole!). Now I have about 50 holes to fill.

My question is: It seems vastly more efficient to cut out big panels and fill with a single piece than try to meticulously fit 25 small plugs. Again, see pics: I have outlined where I plan to cut and patch with fresh metal. Alternately, I could just cut out the panels and overlap with fresh metal, either welding or bolting the edge to the remaining lip of original metal.

Comments?

[Dan in Pasadena]

I’d say your choice depends on what you want the finished result to look like. In my case on my ‘55.2 I literally just stopped counting at 50 holes. I wanted the factory embossing patterns on the firewall and not a flat panel.

So we filled each individual hole - NO “overlapping metal”. All the plugs were cut to size and butt welded by mig tack welds, flattened, allowed to cool to avoid warpage, and the next tack or two placed. This involved jumping around from hole to hole but in the end it came out great and I am very happy I chose this option. YMMV.

[Jesse Z]

Like Dan says, "it depends." Do you want a show car or a driver? Do you want to be driving it in 6 months or 6 years? Personally, I'm too old and I've built too many cars to spend too much time meticulously grooming something that will seldom be seen. I used to think I'd own a car forever so I'd better make it perfect. Now I realize that's rarely true.

My choice would be to cut along your line and overlap a nice piece of polished stainless or diamond plate aluminum on it using a series of equally-spaced chrome button-head bolts around the perimeter. Easy and purty.

If you insist on butt welding then I'd go for one big patch on each side - the welding distance around all those little circles really adds up, so you may end up with less total weld that way.

[mr48chev]

Another option might be to cut out some tight fitting patterns of those three areas that have all the hoes that fight inside the indents and then use the patterns to cut out some aluminum or stainless panels that could be laid in the areas and maybe have a layer of gasket material behind them. I have an aluminum sheet on my firewall but it doesn't seal very well. One of those quick throw together I'll take care of it right later things that never got taken care of. What ever you do do it right and only do it once.

[gigamanx]

I posted a couple of weeks ago with a very similar question. Hope the answers help...

http://67-72chevytrucks.com/vboard/s...d.php?t=747749

[Dan in Pasadena]

MiraclePieCo,

Another option I should mention that applies to the Task Force trucks but I’m not sure if it was ever available for the Advance Design trucks (DOesn’t mean you couldn’t develop one for yourself):

Somebody used to make a Fiberglas firewall cover that bolts OVER the firewall and fit under the pinch weld along the top of the firewall. It was mounted using the four hood hinge bolts on the ‘55.2-‘57’s. I know because I knew a guy that used one for his and you couldn’t tell it wasn’t the stock firewall unless you were looking for it. I looked awhile ago for myself (trying to think of the aftermarket company....it’s out here in California, I want to say in Riverside or San Bernardino) and they were no longer selling it.

EDIT:
It’s No Limit Engineering and apparently has moved to someplace called Dandridge, TN

[_Ogre]

unless your going to finish and paint the inside of the firewall, the plugs don't need to be meticulously cut to butt joint in the hole
i used square cut metal to fill most of the big holes, i see 9 holes in your firewall that need metal filler
anything under 5/8'' can be plug welded using a copper or brass backer bar, mig won't stick to either

[MiraclePieCo]

Originally Posted by gigamanx

I posted a couple of weeks ago with a very similar question. Hope the answers help...

http://67-72chevytrucks.com/vboard/s...d.php?t=747749

Wow, thanks for that link. There is EVERY possible method mentioned, including the Unholes. Gives me a lot to ponder. Thanks again!

[MiraclePieCo]

Officially committed now to "one big hole:"

[Rickysnickers]

Originally Posted by MiraclePieCo

Officially committed now to "one big hole:"

[Black_Sheep]

Originally Posted by _Ogre

unless your going to finish and paint the inside of the firewall, the plugs don't need to be meticulously cut to butt joint in the hole
i used square cut metal to fill most of the big holes, i see 9 holes in your firewall that need metal filler
anything under 5/8'' can be plug welded using a copper or brass backer bar, mig won't stick to either

That looks so nice Ogre, great job shaving the pinch weld too

[MiraclePieCo]

Got the panels cut and plug-welded from the inside. I'm liking how it (unintentionally) mirrors the factory overlapped seam right above it. This method may offend some purists, but it was a quick way to do it without precisely fitting pieces for butt-welding, and it's much cleaner on the inside too, as long as one doesn't care about OEM-type restoration - but that ship sailed on this vehicle long ago! I have some welds to touch up, then will apply seam sealer around the perimeter and start reconstructing that butchered steering column hole.

[gigamanx]

Originally Posted by MiraclePieCo

Got the panels cut and plug-welded from the inside. I'm liking how it (unintentionally) mirrors the factory overlapped seam right above it. This method may offend some purists, but it was a quick way to do it without precisely fitting pieces for butt-welding, and it's much cleaner on the inside too, as long as one doesn't care about OEM-type restoration - but that ship sailed on this vehicle long ago! I have some welds to touch up, then will apply seam sealer around the perimeter and start reconstructing that butchered steering column hole.

Fantastic fabrication job. I really like the idea of two smaller panels keeping some of the lines of the firewall as opposed to slapping one giant piece on the whole thing.