Holes in firewall

[JayEstes 172]

Anyone-

 

What are the two large (~1.25in diameter) holes that are oriented vertically (upper right hand of this pic) thru the firewall for? The holes have been "punched thru" and protrude maybe 0.25in in towards the engine side.

 

I have a 302 with AC, and the heater hoses go thru the slot that open up to the hole where the ac evaporator lines go. (left lower center)

 

I can't figure what these holes are for unless the non AC cars use them for heater hoses in a VERY different configuration inside the car.

 

Can someone help me? THANKS

 

Jay

Edited September 4, 2013 by JayEstes

[69shelbycoupe 11]

Anyone-

 

What are the two large (~1.25in diameter) holes that are oriented vertically (upper right hand of this pic) thru the firewall for? The holes have been "punched thru" and protrude maybe 0.25in in towards the engine side.

 

I have a 302 with AC, and the heater hoses go thru the slot that open up to the hole where the ac evaporator lines go. (left lower center)

 

I can't figure what these holes are for unless the non AC cars use them for heater hoses in a VERY different configuration inside the car.

 

Can someone help me? THANKS

 

Jay

Yes those are for heater hoses on non a/c cars

[jkskinsfan 19]

+1 on the Heater Hoses.

[Grabber70Mach 107]

+2 on Heater hoses on a non-AC car.

[LindenBruce 27]

And for A/C applications Ford plugged those two holes with rubber body plugs like you see in various places on the car. Use a little bit of strip caulk on the backside of the rubber plug before you push them in from the engine side. B.

[JayEstes 172]

Thanks guys. Kind of surprised me that there is such a big difference in AC & no AC installs.

 

I do have a plug kit that I haven't broken out yet, I'll check it to make sure i have the plugs for those.

 

And thanks Bruce- I will put some high-temp silicone RTV on them to help seal it up.

[Jimjific 23]

I recently read some bad stuff about using silicone to seal sheet metal. Collects water and will rust it out. I wish I could find the link. I would use something else.

 

Jim

[JayEstes 172]

Yikes. Haven't heard that. Any suggestions for something else to use? Paintable caulking??? I just resurfaced the metal (both sides) and it has been painted with 500deg engine paint. Seems to be perfect now - don't want to mess that up...

[LiLMike 42]

I used RTV silicone around my grommets on the firewall. I used the black in the engine bay and clear in the interrior. I put it on like calk and smoothed it out. it looks fine to me.

[Jimjific 23]

I guess the issue is when people use silicone that has an acid in the curing process. It looks like automotive silicone's don't have this.

 

Here's a link I found with a little discussion on it.

http://67-72chevytrucks.com/vboard/showthread.php?t=556208

 

Jim

Edited September 5, 2013 by Jimjific

[LiLMike 42]

That is an interesting fact.

[buening 63]

In case you need to identify other holes in the firewall:

 

 

 

1 Engine Earth

2 Sealing Grommet

3 Throttle Cable

4 Wiring Loom

5 Brake Line Holding Clips

6 Peg for Shifter Wire Harness Clip

7 Peg for plastic strap to hold brake line (under #5 there is another stud for a like strap to hold the wires to the hood scoop turn signals if equipped)

8 Heater Hoses

9 Punched holes not meant to be there ?? (Evaporator drain hole on A/C cars)

10 NOT A FACTORY HOLE

11 plastic wiring loom retainer

12 windscreen wiper motor earth

13 ground for hood scoop mounted turn signal harness

14 grommet/loom wiper motor

15 point to clip plastic strap onto

16 grommet heater motor wire

17 wiper motor mount

18 brake master cylinder and pedal support

19 Speedo cable

20 steering column

21 Trans Cross-member

22 Rubber firewall insulation pin

23 Harness from underdash wiring to engine feeds and alternator/battery area

24 heater box

25 Accelerator pedal screw

26 Accelerator pedal screw

 

 

 

 

The above pic is a non-A/C car

[JayEstes 172]

Oh wow! Thanks guys! I appreciate the input on all counts. And buening, thanks for the documented pic! Very helpful. If I get there, I'll try to repost with changes for AC car. Great info - thanks to all.

 

Jay

[buening 63]

The one with A/C should be similar, see below for a decent pic. He heater motor hole is elongated for the A/C lines to go through the firewall, you have a few grommets just below the firewall lip for the A/C vacuum lines, and a few studs with large metal washers near the heater/AC box that mount it to the firewall

 

[JayEstes 172]

Thanks yes, only a few changes would be expected.

 

ALSO, I believe the hole(s) marked #9 should be a heater core/AC evaporator condensation drain line... The AC cars have a tube that drains from the bottom of the heater core/AC evaporator. This prevents significant water buildup from condensation from AC operation - especially in humid climates.

 

Jay

[buening 63]

Correct on the evaporator hose location for A/C cars. I basically stole that pic from another forum and identified the holes for someone else a few months back.

[LindenBruce 27]

Yes, you can use this on the back side of the plug if you don't want to use silicone. As an FYI this stuff is used at various other locations around your car. And it's great for sealing your gas tank down to the body too. B

[69RavenConv 286]

Yes, you can use this on the back side of the plug if you don't want to use silicone. As an FYI this stuff is used at various other locations around your car. And it's great for sealing your gas tank down to the body too. B

 

+1 This stuff is/was used all over these cars. It's good stuff and never hardens. You can get it at any good body shop supply house.

 

[miketyler 15]

Good firewall diagram B, will need to save that for future reference! I think you can pickup strip caulk at Home Depot.