Well, I drove quite a lot today. Still, no one-hour non-stop trips, but several trips with short cool downs between trips. I did tape off the input side of the passenger side plenum with clear packing tape...Bubba would have been proud!

The results, pretty damn comfortable all day long. No heat soak, no difficulty with hot starts, interior was comfortable all day. My wife even commented on what a difference there was. Several times today I reached under the dash and the steering column was not blazing hot at all.

Could it be as simple as timing and having an adequately rich mixture???

John

 

Do you have pictures of where you taped things off ?

 

Sorry, I don't, but I covered the screen on the passenger side completely. I covered the screen from the bottom of the windshield wiper trough all the way up to the fender. I tried to cover it enough that no air could get down there from that route. I was trying to determine if I had any air coming in from open seams in the firewall, plenum, etc. it does not seem that I do, but the jury is still out. Obviously, this is a temporary fix, I still need to get the HVAC system working correctly. I am assuming that the kick panel vent will be closed under any setting other than vent.

I know for certain that the door at the top of the plenum closes only when the controller is set to Max AC, but I am not certain when the kick panel should be open or closed based on the HVAC controller in the dash. Anybody know?

John

 

LOL! It is, what it is! I think I'm gonna have to shield the whole back of the engine.

 

Yeah, it sounds like what is needed is a full thermal barrier added to the front of the firewall and floorboard...that is absurd is what that is.

The more we dig into this issue, the more confusing it gets. Have you tried taping off portions of the vents yet, to see if that makes any difference. I wonder if you got one of those wireless thermometers like they sell for houses and mount the sensor in the engine compartment with the receiver in the car??? Then you could read air temperatures in real time as you were driving, stopped at a light, etc. We know the engine gets hot, we are more concerned with free air temperature and circulation. The problem with that may be finding a remote thermometer that had the range to display the expected temperatures.

An interesting thought though. It would be a true measurement of the effectiveness of the ram air system as well as changes to the vents. Just throwing it out there...

John

 

Just to be clear, if you open the hood and stand on the passenger side of the car and look down into the windshield wiper trough, there should be a screeen there to keep the leaves, etc out of the plenum. I taped off that entire screen from the floor of the trough all the way up to the fender. This essentially blocks off all outside air from getting in through the vents or HVAC system. It was interesting that it made such a difference...now I just need to figure out how to fix it correctly so it doesn't look like Bubba was there.

John

 

Thanks John! I thought that's where you were talking about but I'm a visual kinda guy so I just wanted to be sure.

Having said that I don't think I have any air coming in through my vents but will have to tape something to the kick panel area to see if I do to be sure. I did by pass the heater core since it was leaking and that did help some with the heat so when I can get my HVAC going I will put valves in-line with the heater hoses to shut them down in summer months (well here in TX that will be April through early December).

I really think the main issues are the floor boards and firewall as well as the steering column. As I've stated my plan is to spray Lizard skin as high up the firewall as I can reach, put the tranny tunnel insulation in along with the house collar for the bellhousing, new headers/exhaust w/header wrap from the collectors back to the tranny cross member and maybe wrap the steering column above and below the rag joint then go from there.

 

Ram Air, later this week or better yet, I may just go with the simple laminar flow scoop, directly attached to the lower frame to aggressively push cold air, up and through the engine compartment with velocity to match.

I'm also going to tape off that plenum as well. That will be done by Thursday and testing by the weekend.

John, thanks for posting the results of the taping. Happy to hear that it was more comfortable and getting the second opinion from the wife was good too, because if she's comfortable, you're comfortable! I also agree with Airborne on the vents. I'm not feeling a whole lot of air coming out, but I did find a major leak in the driver's door weatherstripping on the bottom (that I replaced!). I could feel a most definitive draft blowing on my ankle, while I was driving at 55 mph+.

Airborne, I agree with your approach to the lizard skin and want to see how it works as well. Too late for me, but it might work for others. The firewall is a problem! Just pointing the IR gun at the firewall got me 170 degree plus and that was a few inches to the inside of the outer support plate!

 

In 72 it is the same line that has vacuum on 'max ac'. It's tee'd right before the firwall. One line goes to the actuator behind the kick panel, and the other line goes through the firewall into the engine bay, and over to the fresh air door.

 

After I experiment with either the Ram Air or Laminar Layer Scoop, I will be renting a FLIR imaging device and getting a complete picture of what my engine compartment and interior look like, heat wise

http://www.thermalcamerarentals.com/flir-e40.html


I think we've reached the point, where hard data is needed. There's too much to cover with an IR gun and I think the thermal imaging will help showing what's going on with the heat.

 

WOW, that's a good chunk of change, if you have pay pal I'll kick in a few bucks to give a brother a hand...

 

When I redid my interior I installed insulation and wrapped the exhaust system from headers to tail pipe. YES there was a significant difference.

 

Been a long time and yes, an old thread, beat me with a stick, but I finally succumbed and I'm doing the same thing, i.e. wrapping my exhaust headers with the DEI Titanium wrap and stainless fasteners from Ebay.

I was finally convinced by a bud of mine, who races circle track stock cars and while at his house, I saw that his exhaust was completely wrapped with the DEI and as you mentioned, it makes a difference. I also have a brand new unused set of Hedmann Headers for the D-port ZZ4 - L98 - LT1 heads, that are specific to the C-3 Corvette, just sitting there. I brought them, months and months ago and I might as well put them on.

I'm going to wrap the new headers BEFORE installing them and then, I've got to rip out the brand new exhaust system the '74 came with, because an idiot put it in and ran it waay too close to the trans and inner corners of the footwells, while missing the under car heat shields entirely. Also ordered the superb exhaust gaskets from Remflex, that are made of 1/4" crushable graphite. They killed the exhaust leaks I had, from running the old headers, to the L98-ZZ4 heads!

I am still going to try the ram air as well. The hood grills work really well at getting rid of the residual heat and I may just offer them for sale in a month or two. Of course, when I'm done, I'll see if that steering column floor bezel, is still hitting a 150 degrees or not!

Finally, sorry for the long absence. I miss this place, but the Shop has been full-on crazy and we've got a long line of clients waiting to get in the door. I spent six hours this week, alone in the empty engine bay of a '68 Impala SuperSport grinding and sanding, while straddling the cross member and this car has a $5K or $6K custom paint job on it (hint: run the air hoses and electrical, from under the car, not over the fenders!

Thanks all!

 

Hey F22, glad to see back on here! I think I'm going to wrap my new headers before I put them on as well, I was wondering though how close to the header flange the wrap should go? While I can't look at the car right now (at work ), I can imagine that if you wrap it too close to the flange it may make it difficult for the header bolts to go on our may interfere with spark plug installation...

 

I thought about that too. I don't think you're going to have a problem with with wrap itself, as it's pretty thin. If anything, it will be the stainless strap fasteners that might interfere with the bolts. I ordered a bunch from Ebay and they're flat as can be, but I still think you'd want the clamping end, to be away from the bolt holes in the flange and then, I don't think it'd be a problem at all.

Regular hose clamps would look dumb. Cheap, easy, but kind of ugly. The straps they sell on Ebay, look just like the very expensive straps that DEI sells and you're gonna need 8 of them, just for the tops. The hedman headers have a 1 5/8" diameter, so I ordered 3.9" straps for the individual tubes (extra material will help in pulling them tight and securing them, before trimming) and then the 11" for the collector area. About $30 and change for 50 of the 4" and 25 of the 11".

Also, going to do these off the car on the new set. And if I had the old set, I'd probably remove them. Can you imagine doing all that wrapping, in that engine compartment, with the headers on, from above or and below? You might as well be an even bigger sadomasochist than you are now (you have to be one, just to own one and work on it!).

 

Cool deal F22, I have new headman headers as well and if I'm going to do the wrap it's definitely the smart thing to do before I put them in that tights space they call an engine bay! I'll check out e-bay to see what wrap I can get. If you're going to wrap the headers anytime soon please take pictures, I'm not too sure when I'll be doing mine since I would like to do the exhaust at the same time I swap the tranny and I'm not sure how soon that is going to happen (don't ask), but hopefully before summer - we'll see

 

Oooo! A tranny swap? Auto to manual? And yes, I'll take pics. Should be soon. Don't want to die a slow death from heat prostration, everytime I take this out for a long drive!

 

4 speed to 5 speed swap, should of had it already but got taken in the Keisler deal so I'm having to save up the money all over again

 

Where did you buy the Hedmann Headers, and what is the I.D. number. I have a 76 Vette with a ZZ4(355 hp & 405 torque)and would like to install headers. I was told Hedmann was not longer making headers.

 

Is the factory insulated blanket installed on the UNDERNEATH area between your transmission and trans tunnel? Is the factory foam strip that goes between the bell housing and the firewall in place?