Heat...all the time/ plugs - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PitterPats72 · 06-02-2002, 12:28 AM

Ok got 2 questions:

Got the 72 running good except:
1. I got heat coming out all the time. How can I get that turned off (details)

2. got new plugs fro the HEI but been too busy with the deck on my house to put them in. How much difference will that make in performane (speed or MPG (ha)). It seems to not have as much pep as before I got the carb rebuilt and the HEI.

Thanks for the help,
Pat

oleblue72 · 06-02-2002, 02:36 AM

As for the heat I'm assuming you mean the heater?
Is your temp control knob or assembly broken? Has a cable that runs from the control unit thru the fire wall into the heater which opens and closes the hot H2o valve.

As for performance with hei and stuff, my set-up is very mild compared to alot of folks on the board, but a new carb and hei new wires and plugs gapped at 45 made a huge difference in my old 350.
Getting about 13 mpg.

71GMC_3/4T · 06-02-2002, 09:59 AM

For the heater, I think your year has a vacuum operated valve in line for the hot water, if it has AC. It is either stuck (open) or not getting vacuum when your lever is in the cold position.
I took my vacuum valve out and installed a small (can't remember if it was 1/2 or 3/4 NPT) gate valve in the line. Bought a couple of brass heater hose to NPT fittings for it. I open it in the winter and close it in the summer. It's a little inconvenient, but at least I can shut the heat off when I want to.

For the HEI, if you didn't re-gap your plugs from when they were points, you may see a performance decrease. Try your new ones, gapped at .045 like olblue says. You may also want new plug wires, specifically made for the HEI.

BLACK AND BLUE 67-72 · 06-02-2002, 12:01 PM

If you don't have A/C then I would say that the door in the heater box is failing to close, I've had 6 heater boxes apart and I have not seen any water valves, Just cables and doors, Two on the inside box and one on the outside box. Or the rubber seals on the doors in the heateer box could be messed up.

06-02-2002, 12:28 AM	#1
PitterPats72 Registered User Join Date: Oct 2001 Location: Indianapolis, IN Posts: 145	Heat...all the time/ plugs Ok got 2 questions: Got the 72 running good except: 1. I got heat coming out all the time. How can I get that turned off (details) 2. got new plugs fro the HEI but been too busy with the deck on my house to put them in. How much difference will that make in performane (speed or MPG (ha)). It seems to not have as much pep as before I got the carb rebuilt and the HEI. Thanks for the help, Pat __________________ 72 Chevy Custom 10 Deluxe (78K mi.) 95 Nissan Maxima (195K mi.) 73 VW Beetle (owned since 78; 96K miles) Engine rebuild by me done! 73 VW Super Beetle -New to me- Bought from original owner! 84 Honda Nighthawk (2500 mi.) I know too much foreign stuff; I've owned American too and they lasted just as long.

06-02-2002, 02:36 AM	#2
oleblue72 No, U Da Man! Join Date: Mar 2001 Location: Southaven, MS Posts: 284	As for the heat I'm assuming you mean the heater? Is your temp control knob or assembly broken? Has a cable that runs from the control unit thru the fire wall into the heater which opens and closes the hot H2o valve. As for performance with hei and stuff, my set-up is very mild compared to alot of folks on the board, but a new carb and hei new wires and plugs gapped at 45 made a huge difference in my old 350. Getting about 13 mpg. __________________ (sold ole blue 1972) 1997 Dodge 1500 5.9L 1996 Saturn SL2 1.9L 2002 Mitsubishi Montero 3.0L 2005 Ford Escape 3.0L *1967 Olds Vista Cruiser 330-320HP*

06-02-2002, 09:59 AM	#3
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	For the heater, I think your year has a vacuum operated valve in line for the hot water, if it has AC. It is either stuck (open) or not getting vacuum when your lever is in the cold position. I took my vacuum valve out and installed a small (can't remember if it was 1/2 or 3/4 NPT) gate valve in the line. Bought a couple of brass heater hose to NPT fittings for it. I open it in the winter and close it in the summer. It's a little inconvenient, but at least I can shut the heat off when I want to. For the HEI, if you didn't re-gap your plugs from when they were points, you may see a performance decrease. Try your new ones, gapped at .045 like olblue says. You may also want new plug wires, specifically made for the HEI. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO

06-02-2002, 12:01 PM	#4
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	If you don't have A/C then I would say that the door in the heater box is failing to close, I've had 6 heater boxes apart and I have not seen any water valves, Just cables and doors, Two on the inside box and one on the outside box. Or the rubber seals on the doors in the heateer box could be messed up. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA



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