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MG MGA - Exhaust pipe heat shield

I saw a discussion somewhere of problems with the MGA exhaust pipe burning the plywood floor boards. I can't find the source, perhaps it was on this BBS?

The answer seems to be to frabicate a metal heat shield for the driver's floor board; or, to increase the bend in the pipe to give more clearence between the pipe and the floorboard.

What I need to know is what size should the heat shield be? What length and what width. I assume that aluminum would be the choice material. My wife just threw out a well used cookie baking sheet. I grabbed it up thinking it would make a great heat shield because it is a double layered affair with about 1/4" air space between the top and botton aluminum sheets.

Any ideas on this problem?
H Speer

I made some heat shields using aluminum sheet from the hardware store. I sandwiched a couple pieces of fiberglass cloth between two aluminum sheets with a 1/8" spacer between them with pop-rivets. The shields were mounted to the floorboard with wood screws with another 1/8" spacer between the wood and shield. I did not want to create a water trap. They seen to work fine.

I don't remember the dimensions but the were made to fit what seemed right at the time. I made two shields just to be sure. Image attached. I later replaced the exhaust clamp with a strap type from Todd Clarke.


Jim Ferguson

I purchased a small role of aluminum flashing. I had in my collection of STUFF a small roll of ASBESTOS used for lagging pipes. I folded the aluminum sheet in two and put asbestos in between. I just screwed it to the floor over the exhaust pipe and it really lowered the in cockpit temperature.
conrad sanders

My fabricated heat shield looks very similar to Jim's. However I used only one sheet of aluminum in my installation. I spaced it about 1/8 inch or slightly more away from the floorboards using washers. I also bent the edges downward slightly to allow more air to slip into the space between the floorboards and the shield.

BTW...when I got the car there was a hole under the driver seat in the floorboard about the size of a golf ball, burned from the bottom up.

Ray Ammeter

I made a heat shield for mine. I bought a piece of galvanized dryer vent tube or stove pipe (can't remember which)and cut it to a length of 19 inches and a width of 5 inches (or maybe it was 5 inches wide). I welded two u-bolts (the size of the exhaust pipe)about 10 inches apart in the middle of vent piece and attached it to the exhaust pipe under the driver's floorboard with the curve downward. It relects heat downward and since it doesn't contact the frame, heat is not directly transferred and air can pass between the top of the shield and frame. I also painted the floorboard white.

I go the stuff at Home Depot in 2001 for $5.87 or so including tax. It is getting a little beat up after a number of years but it still works.
Bill Haglan

I will try again on the picture.

Bill Haglan

Thanks for all the information guys. The floorboards are out of the frame so it should be easy to rig up something.
H Speer

You can also use many of the hat insulation materials available from the race car outlets. Summit sells them and locally in Vancouver, Mopac in Langley has them.
Bill Spohn

I have never found it necessary to put any heat insulation under the boards. I have just had a close inspection. The gap between the boards and exhaust pipe is just sufficient to get my fingers in between, about 3/4 inch I guess. 12 years on and not a sign of any scorching or discolouration. Would that have anything to do with the polyurathene-type of varnish I applied?

Steve Gyles

Maybe the front pipe only gets hot enough to risk charring the floorboard when the engine is heavily thrashed at high revs. I seem to recall seeing pictures of an engine minus exhaust manifold and the length of exhaust flame was greater at higher revs. Perhaps you are a civilized driver Steve? mike
m.j. moore

More likely occassion for charring would be idling, where there is no air flow to take the heat away from the pipe and the floor.
Art Pearse

Henry, when I purchased my Coupe there was a burn hole all the way through the drivers side floor board about 2"x3". During the restoration I manufactured heat shields from 6" wide x 1/8" thick aluminum sign blanks. I turned the edges down 3/4" for strength and addached them to the floor rails with 1 1/2" x 1/4" machine screws with countersuck heads. I split the distance between the exhaust and floorbaord and used nuts and washers as spacers. Far easier on a restoration with no body on the frame but you could do the same thing through the floor boards at the frame supports.
I'm also planning on covering all the floors, transmission tunnel and firewall with Dynamat Exteme for additional heat and sound insulation.

Good Luck and cooler driving,

Andy 60 Coupe almost

Andy Preston

It was -5 degrees Centigrade here this morning. The underfloor heating was necessary!!
In truth, I think the exhaust will only burn the floor if it has been knocked and comes into contact or at least close proximity with the floor. After replacing my floors a few years ago (with localized burnt hole) I have had no trouble.

Neil Purves

I have regularly given my car a good outing, and to date the floor shows no signs of even the paint blistering. Can't understand why a correctly mounted exhaust would burn the floor, do you guys have the silencer /muffler under the left hand seat?

dominic clancy

I mounted a steel sheet on the ends of the floorboard screws, using additional nuts over the captive ones. This resulted in an air gap of about 1/4" between the steel and the floorboards, and about 1/2" between the exhaust pipe and the steel.
I did this not to prevent the floorboards from burning, but to lower the temperature under the drivers feet and seat. My steel sheet went up the toe board also. Has worked great for more than 20 years.
P.S. Where in BC are you, Henry?
P. Tilbury

I guess BMC got it right by putting the exhaust on the left side of the engine. We do not have the driver's underfloor heating problem with our right hand drive cars!!

Now, hot gearbox tunnelling - that affects us all.

Steve Gyles

My concern before installing heat shielding was that unnoted trauma to the exhaust pipe--produced perhaps by bouncing up over a too-steep ramp, or by catastrophic stuctural failure from accumulating rust--might compromise the dimensional requirements of the original design and lead to a blistered bum, never mind the paint. But as neither have yet happened, possibly I've wasted my time.

Ken Korey

It isn't an MGA (yet) but on my Sprite I used a 4" x 48" piece of sheet steel and (very much like Bill Haglan) wrapped it around the top of the exhaust and just clamped it in place with 3 common exhaust clamps. In between the clamps the metal was loose (but didn't rattle at all) and stopped virtually all of the radiated heat on a trip from Seattle to Missouri and back last summer, made the trip MUCH more comfortable.
Bill Masquelier

This thread was discussed between 05/12/2008 and 14/12/2008

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