taming engine heat at the firewall

[gbhrps]

Having spent the summer past driving a friend's 57 on some very hot days, I was amazed at how hot the footwell got, particularly around the accelerator. I recall that I actually had to change my shoe position on the accelerator, every so often, to prevent the soul of my shoe from burning the bottom of my foot. I'm putting my newly restored 55 on the road this summer and I'm concerned about it being even hotter, due to the lack of side air doors in the kick panels. There is only so much foil and insulation that can be put under the carpeting, and I'm wondering if there could be something done with the exhaust pipe's nearness to the firewall and cabin floor. My wife's Lexus and my Subaru Outback both have heat shields between the exhaust pipes and the floorboards. Has anyone tried to do the same thing with a small bird, and if so, how did you go about it , and what results did you have? Obviously, this would only be adviseable for those of us whose cars are used as drivers, not show cars. Any ideas out there?

[nomadbird]

When you correct one problem area; another one surfaces. The use of a "Dynamat" type material on interior floor and firewall surfaces offers some relief. The addition of a flat piece of sheet metal on top of the frame to deflect exhaust system heat also helps.

A couple problem areas that are elusive: (1) isolating the exhaust pipe heat from the toe board. (2) Isolating the conducted heat on the gear selector housing. That devil gets hot! Almost bad enough to burn you after a few hours of desert driving.
Immediately after my cars were finished and I wanted to minimize wear; I drove in stocking feet. That works for maybe ten miles. Now I wear thick soled walking shoes with the heels rounded on the back edge.

The only thing that seems semi-reliable is to drive the cars only when it is less than 60 degrees F. Then all you have to worry about is freezing your left knee and left ear.

But----they are pretty, aren't they! Tom

[ 01-09-2003: Message edited by: nomadbird ]

[gbhrps]

I appreciate your reply and intend to insulate the floor as much as is possible and practical. The gear selection housing heat is a problem that can't be corrected. But I see no reason why carefully made heat shields can't be used to cover the exhaust pipe from toeboard to behind the seat area. I'll have to give this thought, after I get the car reassembled and check for clearances... and the practicality of the entire exercise. I sure don't want to be drilling holes in the frame to attach heat shields, but I think they could be clamped to the exhaust pipe itself. Thanks for the hint on the shoes!

[stephen]

I've played with this quite a bit. Heat shields don't help much because there's not much space. Air space is the buffer you need, and we just don't have it.

I've found that blowing air IN through the cowl doors doesn't help much either (usually becuase it's hot air, too), but taking air OUT does. Here's a post for the "I don't mind a little modifying" crowd.

I have taken this system out, becuase it's winter and the cowl vents get used a bit, but it was great this summer. The '56 and '57 have fiberglass fittings that go through the itside body to the vent doors. I put small pipe duct fans in those fittings, and removed the plastic duct between the door and the cabin. Hit a switch under the dash, fans come on, suck heat out from under the dash, and blow it out under the car.

In winter, I put the duct back because it's more beneficial to move cold air in than to evacuate the warm, and this works better from outside the car than between the skins.

Cheap. Easy. Effective.

This could be done in a '55 pretty easily, I'd imagine.

[nomadbird]

If you want to try heat shields, there are a couple principles to keep in mind. The goal is to isolate both convective (movement of heated air) and conductive (touching the heat source) thermal paths. The inside heat caused by the exhaust system is an example of convective heating and the gear selector housing heat is an example of conductive heating.

The most effective way to isolate a thermal path from the heat source to your body, is to place a shield between the source and the body without touching either of them. Clamping shields to the exhuast pipe will help somewhat but you are heating the thermal isolator. That is not a good thing.

I believe it is possible to optimize a thermal isolator by placing a piece of sheet metal on top of the frame rails and continue running it up the toe board as far as possible. This isolator may be clamped to the frame using the same scheme as used for attaching the hood scoop block off plate. On the drivers side it can be run up to the underside of the master cylinder and clamped to the steering column. On the passenger side, it would be attached to the frame in the same manner and the top could fastened to an outrigger bracket mounted to the underside of the heater duct. That is probably the optimum as far as thermal design is concerned.

If you still want to clamp baffles to the exhaust pipe, you might want to try the following: '55 Chevys with power steering had Shield Assemblies` mounted on the exhaust pipe to protect the power steering hoses. Their part numbers are 3715008 and 3715004. I believe 3715004 is the longer of the two. These items should be available from most tri-five chevy parts suppliers. Just because GM did it, doesn't mean it was right. Remember, these are the same folks who had fuel filters and oil filters as options in '55.

Keep Cool, Tom

P.S. The baby birds have a couple examples of reasonably good thermal isolators in the engine compartment. One of the most obvious is the master cylinder "drip pan". You wont find this item on passenger cars. Another example is the sheet metal piece next to the battery. The Y-Blocks have heat shields protecting the spark plugs too.

[ 01-10-2003: Message edited by: nomadbird ]

[gbhrps]

Many thanks for the informative replies! I'll continue to do my homework on the heat problem, and I'll get back to this thread if I come up with anything positive.

[McNamee]

I used the foil insulation under my carpet and firewall(summit or any T-Bird supplier can get you the stuff) and it really cut down on the heat and noise. However, while it cut down on the heat, it did not eliminate it. It still gets a little uncomfortable in bumper to bumper traffic in Atlanta in the summer.

You may want to try a product that should be the "ultimate" in heat protection for the interior. It is expensive, but they already make an 8-piece pre-cut kit just for the thunderbird. The web site is www.koolmat.com, look under "new products" for the T-bird listing and prices. This stuff is only 1/10 of an inch wide, but should work better than the foil (if you can believe what's posted). If anyone uses this stuff, let me know, as I'm going to do a body-off, and might want to upgrade my heat protection in the cockpit.

Thanks,

Mike McNamee
1957 Starmist "Nadine"
Roswell, GA

[gbhrps]

Thank You Very Much! I'm going to check this out!