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No hair on my legs!!!!

C

cmegga

Guest
Seriuosly I cant take the engine heat burning my legs anymore. If anyone has found a way to prevent the engine heat from cooking you legs .. please please please let me know.

Its 90 degress and for the first time I almost do even want to drive the thing.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Hmm,

Believe it or not, on my 69 with sidepipes, the cabin heat is minimal. You can feel heat coming around the windshield out of the cowl induction hood area, and side gilles, but is fine inside.

I credit this to the sidepipes. They vent the heat out from under the car.

I also seal shut the incoming air ducts on the cowl for the vent system.

I also have a heater cut off valve.

Is yours working? You need to make sure that the control valve is shutting off the hot water flow to the heater core in the dash.

That should help a ton. Plus sidepipes would be cool, but then you would be loosing the skin off your legs when you get out in a hurry and forget to step clear of the pipe!
 
Joined
Aug 29, 2001
Messages
3,234
Location
Norcross, Georgia, United Stat
Corvette
2017 Arctic White Grand Sport
Chris,

How did you shut the incoming air ducts on the cowl and where does the air for the HVAC system come from with them closed up?

The sidepipe issue is a good observation. After running for an hour or so I can feel the heat coming from the drive train tunnel, which I assume is substantially heat from the exhaust.

Which insulation did you use when you insulated under your carpet. Did you get this thin expensive stuff or did you use the regular stuff that is fairly reasonable.

Bob
 

77-4speed

Well-known member
Joined
Apr 30, 2002
Messages
249
Location
Houston, TX
Corvette
1977 Black L-82 4-speed
Here is the formula for no more engine heat:

1) Make sure factory heater cut-off is operational, or install heater bypass valve in both heater hoses

2) Remove interior carpets and seats

3) Seal off all firewall Grommets and holes

4) Seal off all floorpan or any other holes

5) Make sure all factory insulation is present (transmission tunnel and collar)

6) make sure lower shift boot is not torn

7) Make sure upper hood seal is in place

8) Make sure fresh air vent is operating properly

9) Apply heat reflective material to interior covering ALL of the floorpan and any place you can reach

10) Make sure A/C-heater box seals are all good

11) Make sure all tar-type material is in place and sealing in the wiper door area so that no air can enter.

12) Have your headers and exhaust coated with Jet-hot or the like.

I think that is about all of the repairs you can do to make sure that the hot air entering the cabin is remedied.

Russ
 
Joined
Aug 29, 2001
Messages
3,234
Location
Norcross, Georgia, United Stat
Corvette
2017 Arctic White Grand Sport
Good list Russ. I'm going to have to print it out and use it as a checklist :r as I knock them out.

I'm still trying to get my hands on the cooling strategies book done by Michael Haynes, but the two places that list it can't seem to get it in stock.

Bob
 
7

78SilvAnniv

Guest
Thought you had sidepipes...

I was SURE you had burnt the hair off with sidepipes!

I have had only one time of driving the 78 when she cooked my legs good. It wasn't really her fault...it was the AC shop's fault. I took her down and waited for completion, but they needed a part and asked if I could come back in 2-3 days. I said "sure, button her up and I'll head home".

Home was just over an hour away. In the height of afternoon summer temperatures in northern California. When I got home, I had 1st degree burns on my lower legs. Bright pink for several hours. I called the shop and they asked me to bring it in for them to look at and fix for me...I said "NO WAY AM I DRIVING ANOTHER HOUR UNTIL THIS IS FIXED!"

Anyhow, I spoke with a tech on the phone and described the engine bay to him, and he suggested a place I could cover with tinfoil covered cardboard and duct tape.
I had been getting engine heated air blown on my legs. :(
Long story short, AC is fixed. However I still rarely use it, I like the humidity and air blowing on my skin as I drive.

Besides sheilding the carpet, the heaterhose cut-off is a grand idea. This spring my heater core blew, and while I am waiting for Kenny to have some spare time from work (fall) my heater has been bypassed. I have noticed a marked difference in cabin temperature!
Heidi
 
T

True Duals

Guest
Here was my answer to all the heat in my 80. I pulled all of the carpet and got a roll of HVAC insulation. This material looks like bubble wrap with foil on it. I cut and used 3M spray adheasive and placed it through out the car. I then installed the new carpet and away went all of the inside heat. This was all done for under $50. Good luck
 
C

cmegga

Guest
Great advise guys , I will definitly line under the carpet this week.

I would also like to check the control valve too see if itis shutting off the hot water flow, what chris talked about. Wondering if anyone can direct me a bit better on where I would find this and how to check it. I thinks hes refering to the sliding heat control under the dash, which is easy enought to get to if im doing the carpet anyway. buy how can I be sure its off ?? It does not blow air threw until shes nice and hot and even then there is not air flow just heat and lots of it.

I dont remember it being even close to this bad last summer.
 

77-4speed

Well-known member
Joined
Apr 30, 2002
Messages
249
Location
Houston, TX
Corvette
1977 Black L-82 4-speed
cmegga,

I think Chris is talking about a manual shut-off valve that most of us have installed in the heater hose going from the manifold to the heater core. There is a stock one but they only close when the a/c is turned on. If you are not getting any air blowing on you, I would check the following very closely:

floorpan for any holes
lower shift boot (under the shift console)

These two things can really radiate heat into the cabin.

Also, if you have headers, seriously think about having them coated and also the exhaust pipes either coated or wrapped. As Chris mentioned, the sidepipe guys have a much cooler ride :)

Russ
 
Joined
Aug 29, 2001
Messages
3,234
Location
Norcross, Georgia, United Stat
Corvette
2017 Arctic White Grand Sport
Cmegga,

When you say she doesn't blow air, do you mean no air is coming through the vents even with the fan on high?

The heater valve is in the heater line as Russ mentioned. It will have a small vacuum line that looks like a wire coming out of it. I pulled this valve and went to Ace Hardware and got a small brass valve that had threads on each side for different size lines and got the right size barb fittings to match the hoses. I think there were either 1/2 or 5/8 inch but can't recall for sure. I also capped the vacuum line with a small screw to prevent vacuum leak.

Bob
 
S

sac001

Guest
I must be a bit dense, cause it seems like we are talking about a few different fixes here.

I understand adding insulation under the carpet, makes sense.

I'm not sure I understand the heater cut off valve. Is there supposed to be one from the factory that is prone to failure, and are you discussing a bypass of that system, or just how to repair that system? :confused

If there is a repair to the factory system, I'd love to see it as I too get warmed by the engine, like it or not. :cry

I would also like to see how to bypass the heater core and not have problems with overheating and the heater core rusting out.

Can those of you that have done this mod/repair write it up and post it in the tech section so we can learn from your experiences, it would be a great help to many, myself included. :beer

Steve :w
 
Joined
Aug 29, 2001
Messages
3,234
Location
Norcross, Georgia, United Stat
Corvette
2017 Arctic White Grand Sport
Sac001,

I'm not sure of what they are looking for in the tech section. I can comment on the heater valve here and if someone wants to copy and paste it, add to it, correct my information, etc, feel free to do so and post it.

All I can speak to is the 77, though I understand the set up is common to most if not all of the sharks. I am not 100% sure on this stuff as I have pieced it together from visual inspection of my system, examination of the AIM and from various, sometimes slightly contradictory posts here.

The basic concept is simple. Press the temperature slide control all the way to cold and vacuum is released which closes a water valve in the supply side line to the heater core line and prevents hot water from getting to the heater. There are suggestions that this only works when the a/c is on but I didn't see anything in my system that would prevent it from doing this anytime the slider is slid to the left.

The workings are a little more complicated. As I understand the thing, there is a vacuum valve on the top of the ventilation box that contains the heater core. This is up behind the lower passenger side dash pad inside the car. When operated mechanically by the spring loaded wire attached to the temperature slide releases vacuum it releases the vacuum that controls the valve in the heater line.

When you go all the way to cold with the temperature slide on the console, the valve, which appears to be part of the hardware for the door that controls the amount of air flow over the heater core, is activated when the spring loaded wire that snakes out from under the console and around the duct work moves the air distribution door to a position that bypasses the heater core. It appears to be a plunger type of valve that releases vacuum when depressed by the pressure on the wire from the temp slide at the same time that the temperature door prevents hot air from entering the ducting.

It is important to adjust the spring loaded wire using the turnbuckle on it to make sure that this vacuum valve is activated before the slide gets all the way to cold. If not properly adjusted, the slider will hit the left stop on the console before striking this vacuum valve and will not allow the valve to release vacuum.

The vacuum runs from an unknwon source through this valve and out a wire sized hard plastic vacuum line that was white originally (mine was yelllow now due to age). I'm not sure of this but I think it goes into a fitting at the firewall and comes out the other side as another small vacuum line. In any event, it comes out high on the firewall right behind the distributor and snakes its way along the firewall and insided right fender to about 2/3's of the way to the front of the car and then goes down and attachs to the vacuum valve in the supply side heater line. When activated by vacuum, this valve stops the flow of hot water to the heater core.

I replaced the deteriorated vacuum line with a bigger rubber vacuum line by cutting it back as far as I needed to, got the rubber line at a VW dealership, and slipping it over the end of the plastic line. It also slides over the fitting on the heater line valve without the little grommet that is already on ther. I had a new vacuum valve for the heater line and bench tested it before putting it in the car using the line from the car. I had six pounds of vacuum and when I bench tested the valve it appeared to activate the valve and would prevent water from going to the heater core.

I put the unit back in place in the heater line, took the car out for a spin and was disappointed to find out that I was still getting hot air. At this point I had had the dash apart for a month and was extremely frustrated.

I took the valve out of the heater line and went to Ace Hardware. The had a good selection of small ball valves, as I recall, that had threads on each end that would accept barbed ends to put a hose over and I got one for each side that matched my heater hose diameter, either 1/2 inch or 5/8's inch and put it in line with new clamps. No more problem with heat coming out of the system at any position on the temperature slide, though I can stop at any time and open the valve and get hot water to the heater core. (I have never had to do this as everyone knows that getting the cabing of a shark hot is not difficult.) The temperature of the air coming through the ductwork is likely 5 or so degrees higher than the temperature of the ambient air temperature and I attribute this to all of the other heat sources that the duct work is exposed to.

The only exception is when the car sits for a while off and the heat builds up in the ducts from, I suspect, contact with the firewall, floor and drive tunnel. Start the car, rurn the fan on high and it goes away in several minutes.

I only used one valve and elected to remove the vacuum controlled valve and replace it with the manual valve as it was not working and I wanted to reduce clutter. Others have simply added the manual valve in addition to the vaccum valve..

I don't know if two manual valves would do a better job or not, though it would be necessary if you have heater core problems.

I'll get the digitial camera out tomorrow and where visible take pcitures and post them on a web page referenced here for viewing.

I apologize for the rambling and typos but is getting past my bed time.

Bob
 
H

Hijinx

Guest
Bob,
Good write up, although I am going to have to go through and really look things over to figure it all out. My '73 blows hot air all the time. I am definately going through and doing your fix. Texas this time of year is no fun and my wife's van is in the shop and I am driving my Shark every day now. Had to replace the carb this week, the Q-Jet gave up the ghost. Ya'll should get a good Demon carb article out of it thought in the Shark Bites column very soon. Thanks for the info. Add any clarifying points you think of.
 
S

sac001

Guest
Bobchad,

Great writeup, thanks for the time and effort, now I think I understand. :)

One more question, if you use the manual bypass valve will the air conditioner work? Mine doesn't currently work anyway, but I plan on fixing it, and want to get everything working as it should.

Steve :w
 

77-4speed

Well-known member
Joined
Apr 30, 2002
Messages
249
Location
Houston, TX
Corvette
1977 Black L-82 4-speed
That's a great summation Bob! The only thing I'll add is the purpose of 2 valves:

When only 1 valve is installed, hot water still fills the heater core through the lower hose. I didn't think it was possible but I checked with my valve in the upper hose closed, and the lower hose was hot all the way to the core. So, installing a valve in the lower heater hose absolutely closes off all flow of hot water to the heater core.

Oh, one other thing. The fresh air vent (for the 77 at least) is located in the passenger side wiper door area, down in the fender well. It is behind the plastic screen. If this vent is receiving hot air (i.e. engine air) it will be pouring hot air into the car as well. This can be kept to a minimum by installing weatherstripping to seal the front lip and first 6" of the sides of the hood. :)

That's all I can add, along with the above "check-list"

Russ
 
Joined
Aug 29, 2001
Messages
3,234
Location
Norcross, Georgia, United Stat
Corvette
2017 Arctic White Grand Sport
Russ, good points on the air flow. I just limited my dissertation to the mechanics of the system. I think I'll add that second valve and see if I can drop the temp down that last 5 degrees.

Steve, Sure does. The valve has no impact on the a/c other than to cut back on the heat in the duct work produced by the heater core.

Bob
 
C

cmegga

Guest
Bob

Really good advise, thanks for all the time writing that up. I do think I need to install this valve. The heater hose that you installed the valve in , is the hose running along my right firewall next to the return form the manifold ??

I just want to make sure im shutting off the right hose, also did you put a valve that completely cuts of water flow??

if you have a picture I would really apreachiate it.
 
Joined
Aug 29, 2001
Messages
3,234
Location
Norcross, Georgia, United Stat
Corvette
2017 Arctic White Grand Sport
I'll take some pics and post them tonight. The valve I placed replaced the existing vacuum line. Take a look a the two lines going to the heater core. One will have a valve and the other won't.

The valve I used completely shuts off the water flow, though as Russ pointed out, hot water from the outlet hose appears to transfer heat back through the core. I'm probably going to put a shut off in that one as well.

Bob
 

Red73BB

Well-known member
Joined
Jun 15, 2001
Messages
241
Location
Defiance, MO
Corvette
1969 dark red convert
I had the same problem. when I replaced the carpets I also installed a heat reflective barrier. These came in precut pieces that I matched up with the floor pan. This simple mod made a huge difference on interior heat.
Gary
 

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