EL CAMINO HVAC to Firewall Fastener size?

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SIC

Not-quite-so-new-guy
Oct 3, 2022
23
17
8
Murder City
Anyone tell me what size fasteners for the HVAC system to the firewall? I have deleted my HVAC system , and I want ARP Fasteners.
Thank you
 

ELCAM

Royal Smart Person
Jun 19, 2021
1,114
1,249
113
What I am finding is GM part number 499558.

Comes up with various descriptions but size is the same.
Screw hex tap (M6.3X1.8 X 35)
Screw Hex tap w/conical (M6.3X1.81X35)

I think this is a sheet metal screw that threads into the AC assembly inside the dash, if you removed the inside part too just use M6 or 6.3mm=1/4" bolts and nuts.
 

SIC

Not-quite-so-new-guy
Oct 3, 2022
23
17
8
Murder City
What I am finding is GM part number 499558.

Comes up with various descriptions but size is the same.
Screw hex tap (M6.3X1.8 X 35)
Screw Hex tap w/conical (M6.3X1.81X35)

I think this is a sheet metal screw that threads into the AC assembly inside the dash, if you removed the inside part too just use M6 or 6.3mm=1/4" bolts and nuts.
Thank you Sir !
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
8,089
17,299
113
ARP is worth the price if you like the attention to detail they pay to their fasteners. They are definitely the cats azz if you prefer both max performance and great looks. I prefer GM fasteners on a restoration because there's no doubt that while they don't always look perfect, I know they will function as designed and engineered and they are more "correct". Just depends on what you're going after.

With that said, I've used ARP studs on 455 main caps, and other fasteners I considered critical during a warmed up BBO assembly. But...I don't think I'd waste the money for holding on an HVAC delete plate unless I was building a show car. In America, though, you certainly have that right to spend your money as you see fit on your car and buy the bolts you want.
 
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Built6spdMCSS

Geezer
Jun 15, 2012
5,695
9,502
113
Florida Beach
Like why? It's just screws that hold a flat plate in place and then ARP, you are kidding right?
Clearly you don't know that you need all that tensile bolt strength for that piece of sheet metal haha.
 
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