Unwanted Cabin Heat
Thread Starter
Intermediate
Joined: Jun 2008
Posts: 25
Likes: 0
Unwanted Cabin Heat
wanting to install insulation under carpet eliminate engine heat coming thru to cabin. Has anyone been succesful in doing this? If so please recommend material and where I can buy it.Also does wrapping ceramic coated header damage coating? Car is a 78 L82 . I live SE of Houstn Tx. and weather gets hot.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
This thread comes up fairly regularly so do a little searching and you fine many ideas to help with the heat.
Undercarpet insulation will hellp a little, but the idea is to keep the heat from getting into the cabin at all.
Do a search for "Lizard Skin" it is a very expensive commercial product that is basically ceramic insulation in paint. It helps a Lot, you aint in on both sides of the floor pans and firewall. There is also a recipe in here to make your own, search for "Micro Spheres". In addition to that, a layer of one of the Fat Mat thermo barrier helps, insulating the AC box is a good idea, you will need to fix the ducts and air flaps in the ducts to stop the hot air from coming in that way, install or fix the hot water cutoff valve, lots of things like that.
Wrapping the headers is also a good idea. The Thermotec wrap is good stuff. It may hold some moisture and therefore might shorten the life of the headers, but I would rather slap on a new set of headers every 4 or 5 years and ride in comfort thatn sweat my *** off with some way cool shiney pipes. The wraps look like sheite but it works.
Undercarpet insulation will hellp a little, but the idea is to keep the heat from getting into the cabin at all.
Do a search for "Lizard Skin" it is a very expensive commercial product that is basically ceramic insulation in paint. It helps a Lot, you aint in on both sides of the floor pans and firewall. There is also a recipe in here to make your own, search for "Micro Spheres". In addition to that, a layer of one of the Fat Mat thermo barrier helps, insulating the AC box is a good idea, you will need to fix the ducts and air flaps in the ducts to stop the hot air from coming in that way, install or fix the hot water cutoff valve, lots of things like that.
Wrapping the headers is also a good idea. The Thermotec wrap is good stuff. It may hold some moisture and therefore might shorten the life of the headers, but I would rather slap on a new set of headers every 4 or 5 years and ride in comfort thatn sweat my *** off with some way cool shiney pipes. The wraps look like sheite but it works.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
I think you've double-posted this one, but I'll give you the same answer as the last time:
On these old cars, engine heat in the cockpit is seldom due to heat coming through the floors and firewall: Fiberglass is an insulator - not a heat conductor, so a 'glass car, by design, actually is cooler than a steel car. The heat that comes into these old cars comes through the dried out, crumbling, rotting seals in the heater box & firewall and leaks into the cockpit through all the rotted seals. The only way to fix it is to pull the entire heater/AC box out of the car, disassemble it, and repair all the damaged seals in the flapper doors and passages. You then need to restore all firewall seals and grommets and make sure things are tight. With the seals all leaking, you can put all the insulation you want in the floor with no real effect on the cockpit temperature.
I worked on these cars and drove them when they were brand new off the showroom floor, and there was never a cabin heat problem. That's because the seals in the firewall and heater box were all new and tight - nobody has changed the floorboards over the years - the floor and firewall are not the problem, and putting insulation over the top of the naturally-insulating fiberglass floor isn't going to buy you much. Fix the real problem by replacing all the seals.
Lars
On these old cars, engine heat in the cockpit is seldom due to heat coming through the floors and firewall: Fiberglass is an insulator - not a heat conductor, so a 'glass car, by design, actually is cooler than a steel car. The heat that comes into these old cars comes through the dried out, crumbling, rotting seals in the heater box & firewall and leaks into the cockpit through all the rotted seals. The only way to fix it is to pull the entire heater/AC box out of the car, disassemble it, and repair all the damaged seals in the flapper doors and passages. You then need to restore all firewall seals and grommets and make sure things are tight. With the seals all leaking, you can put all the insulation you want in the floor with no real effect on the cockpit temperature.
I worked on these cars and drove them when they were brand new off the showroom floor, and there was never a cabin heat problem. That's because the seals in the firewall and heater box were all new and tight - nobody has changed the floorboards over the years - the floor and firewall are not the problem, and putting insulation over the top of the naturally-insulating fiberglass floor isn't going to buy you much. Fix the real problem by replacing all the seals.
Lars
Racer
Joined: Jun 2006
Posts: 476
Likes: 0
From: Easton PA
for me i needed new carpet and such, so i dyno matted everything, 2 layers on tunnel. like nite and day. 110 degrees outside nice on inside plus less road niose. check your seals and maybe look into insulation mat
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
Take a look at this. It cured most of my heat problems.
https://www.corvetteforum.com/techti...=241&TopicID=3
https://www.corvetteforum.com/techti...=241&TopicID=3
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You should also know that there is a rear hood seal that runs around the back edge of the hood and a couple of feet down each side. That seal prevents engine compartment heat from being drawn into the fresh air intake at the right-side of the cowl area. If your seal is old/hard/deformed/missing, it may need to be replaced as it may no longer be doing the job.
As Lars mentioned, the new C3's didn't have any significant cockpit heat problem...unless it was a BB engine and the weather was hot. Even then, if you had A/C, it would cool it adequately and footwell heat was not a problem.
You may also want to check the transmission tunnel insulation (if you have an auto tranny). There should be a heat shield above the tranny and a foam heat insulator around the back of the tranny bell housing. If those are missing, there will be a lot of heat coming thru the tranny tunnel area.
While I agree with Lars that fiberglass is a better insulator than steel, it will still pass heat (it may take longer to get into that cabin, however). The old jute padding under the carpeting did a decent job of insulation. However, after years of compression from use, that stuff is probably no longer effective (if it is even there), so something is needed to prevent exhaust pipe heat from getting through the footwell. I installed Reflectix when I lived in Phoenix, and it does a credible job of insulating that area. There are 'better' insulation systems, but they are much more expensive. Also, there is a big difference between heat insulators and 'sound deadening' materials. The latter materials do little to eliminate heat from the cabin area (although they may delay the heat for a bit).
As Lars mentioned, the new C3's didn't have any significant cockpit heat problem...unless it was a BB engine and the weather was hot. Even then, if you had A/C, it would cool it adequately and footwell heat was not a problem.
You may also want to check the transmission tunnel insulation (if you have an auto tranny). There should be a heat shield above the tranny and a foam heat insulator around the back of the tranny bell housing. If those are missing, there will be a lot of heat coming thru the tranny tunnel area.
While I agree with Lars that fiberglass is a better insulator than steel, it will still pass heat (it may take longer to get into that cabin, however). The old jute padding under the carpeting did a decent job of insulation. However, after years of compression from use, that stuff is probably no longer effective (if it is even there), so something is needed to prevent exhaust pipe heat from getting through the footwell. I installed Reflectix when I lived in Phoenix, and it does a credible job of insulating that area. There are 'better' insulation systems, but they are much more expensive. Also, there is a big difference between heat insulators and 'sound deadening' materials. The latter materials do little to eliminate heat from the cabin area (although they may delay the heat for a bit).
Pro
Joined: Aug 2006
Posts: 649
Likes: 8
From: COOKEVILLE TN
I think you've double-posted this one, but I'll give you the same answer as the last time:
On these old cars, engine heat in the cockpit is seldom due to heat coming through the floors and firewall: Fiberglass is an insulator - not a heat conductor, so a 'glass car, by design, actually is cooler than a steel car. The heat that comes into these old cars comes through the dried out, crumbling, rotting seals in the heater box & firewall and leaks into the cockpit through all the rotted seals. The only way to fix it is to pull the entire heater/AC box out of the car, disassemble it, and repair all the damaged seals in the flapper doors and passages. You then need to restore all firewall seals and grommets and make sure things are tight. With the seals all leaking, you can put all the insulation you want in the floor with no real effect on the cockpit temperature.
I worked on these cars and drove them when they were brand new off the showroom floor, and there was never a cabin heat problem. That's because the seals in the firewall and heater box were all new and tight - nobody has changed the floorboards over the years - the floor and firewall are not the problem, and putting insulation over the top of the naturally-insulating fiberglass floor isn't going to buy you much. Fix the real problem by replacing all the seals.
Lars
On these old cars, engine heat in the cockpit is seldom due to heat coming through the floors and firewall: Fiberglass is an insulator - not a heat conductor, so a 'glass car, by design, actually is cooler than a steel car. The heat that comes into these old cars comes through the dried out, crumbling, rotting seals in the heater box & firewall and leaks into the cockpit through all the rotted seals. The only way to fix it is to pull the entire heater/AC box out of the car, disassemble it, and repair all the damaged seals in the flapper doors and passages. You then need to restore all firewall seals and grommets and make sure things are tight. With the seals all leaking, you can put all the insulation you want in the floor with no real effect on the cockpit temperature.
I worked on these cars and drove them when they were brand new off the showroom floor, and there was never a cabin heat problem. That's because the seals in the firewall and heater box were all new and tight - nobody has changed the floorboards over the years - the floor and firewall are not the problem, and putting insulation over the top of the naturally-insulating fiberglass floor isn't going to buy you much. Fix the real problem by replacing all the seals.
Lars
....makes total sense !
