Stubborn like a man who needs directions but refuses to ask

[3spd6]

Hello square body population,

reaching out from San Diego. Not sure where this belongs but its my first post here. bought a '73 GMC K2500 and had it shipped down as a project. I am in the middle of an engine/trans swap (350/350 to 383/700r4). The heating system is in pretty sad shape missing ducting and vent faces. This is a heat only no AC setup and I figured I would clean this up at the same time as the swap. Here is my problem.

There are two thru firewall hoses that were apparently cut at some point in the past. Can anyone tell me what these are for?View media item 7534
Appreciate any input on this matter.

Cheers and Happy Easter

Greg

 

[PrairieDrifter]

My guess would be a heater core. But that doesn’t seem like it’s in the factory spot. Looks like someone might have done some hacking on the heating system.

Get a pic a little farther back and get one of the passenger side of the firewall as well

 

[HotRodPC]

What does your HVAC Controller look like? That appears to be more of an aftermarket AC set up to me with the Evap coil inside the interior instead of directly in front of the firewall on the passenger side like the OEM AC trucks have.

 

[Old77]

Moved to a more appropriate subforum

 

[Charlie]

 

[Snoots]

Welcome!
Yes, more pix.

 

[Colin]

Too small for heater hoses. Vacuum lines maybe?

 

[Craig 85]

I agree, that looks like hoses for an aftermarket A/C set up. I had something similar on my '80 3+3. The third hose on the left looks to be a condensation drip hose.

 

[3spd6]

Thanks to everyone's response. Here are some more pics to hopefully shed some more light on the issueView media item 7536View media item 7537View media item 7540View media item 7539View media item 7538
The first two show the relationship on the firewall to the heater core and blower motor
The next two pics show items I did not expect to find lurking under the dash. It looks like an additional blower motor sandwiched between the glove box and passenger side wall. The other is some time of small radiator stuffed behind the central passenger side vent.

The controller has not indication for AC and the firewall does not have the oversized condenser housing attached.
So, back to the hoses. Are they relevant? if I don't care about AC should I just plug them. That being the case does the blower motor and additional radiator/heat sink need to be under the dash or should this go as well.

thx

 

[HotRodPC]

Yep, that's just an aftermarket AC system someone has had added. The controls were probably on an underdash unit that appears to have been removed already. All that aftermarket stuff can be removed if you have no intention of AC. It would sure get alot of things out of your way.

 

[3spd6]

thx to everyone. you have been a big help and yes there is a bunch of crap stuffed under the dash. was able to pull the blower but the main part is sandwiched in there and I will have to pull more stuff just to get to it. looks like they tossed a lot of the original ducting components to make room. Is there a recommended vendor for replacement components?
It looks like they may have replaced the main box since there is no window in the front that would feed the vent system. It should be on the front face of the box just to the right of the floor vent. Do I have that right?
View media item 7543View media item 7542View media item 7541

 

[HotRodPC]

I'm not familiar with the Heat only air handler box. Hopefully someone else with a Heat only truck can say that it is or is not an OEM heat air handler. I'd say it looks OEM, but as said, nothing to compare to.

 

[3spd6]

I am basing my guess on this schematic that I located on the web.View media item 7544
looks like there are three outlet points for defroster, heater and for the dash ducts. The box in the truck seems to only have the first two.

 

[HotRodPC]

I am basing my guess on this schematic that I located on the web.View media item 7544
looks like there are three outlet points for defroster, heater and for the dash ducts. The box in the truck seems to only have the first two.

But this appears to be an AC air handler and duct work. I'm fairly certain it's different for the Heat only trucks. I've never had a Heat ONLY truck so I can't say I'm familiar with what you'd need but it seems I looked at one in Pull A Part last summer and they're different. If the ducting is the same as AC trucks, then I may very well have the parts you'll need.

 

[3spd6]

View media item 7545Alright I am changing my position on this. After reviewing the 1973 manual it appears that there is no front window on the heater box. Page 28/979 has a diagram of the box and view "B" appears to be the far (passenger) side of my heater box showing the vent air coming out (this being the third option vs floor & defrost).

So HotRodPC is correct and I have an OEM heaterbox.

This brings me back to an earlier question. Since the AC conversion dumped most of my ducting internals how was this originally suppose to hook up to my four dash vents. Can't find anything online and the manual does not address this.