Melting Fiberglass Bumpers?

[randywebb]

I have a Monty on my '73, which has SSIs and is about to lose the stock steel rear bumper in favor of a FG one.

I've seen threads where other, newer cars ahve had heat problems (Turbos are obviously a different category), but haven't seen anything on the early cars.

Has anyone had problems?

Should I be looking into some heat shielding?

[Todd Simpson]

Yes, I've seen several early cars with RS rear bumpers that have burned from the heat of the muffler. Both were 3.6 swaps that had a custom muffler.

I've never had the problem with a banana style sport muffler. I've got at least a few inches between the muffler and the bumper.

[Maltese Falcon]

Randy, good insurance with hot egts...just get some sheet T304 SS ( 20 ga.) and build yourself a rectangular heatshield under the bumper. Keep the dull side towards the bumper (min 1/2" air gap) and the shiny side towards the heat radiation. Cheap insurance
M Falcon

[billyboy]

Mc Master Carr has ceramic blanket material that comes in different thicknesses and could be inserted between the two. I use it to cover the turbo on my other vehicle which runs at 850 degrees for hours on end. It could also be attached to the inside of the bumper with fiberglas cloth and a white liquid paste material called airbol lagging adhesive. This is how we attach it to exhaust systems that run much hotter than a car.The cloth is not an issue when used without the normal resin.

[911pcars]

The material doesn't have to be so special. I experienced heat bubbling on my steel license plate frame soon after the rebuild. Whether this was from an overly rich or lean mixture setting is unknown, but it got hot.

I fashioned a shield from galvanized roof flashing and attached it to some flat aluminum bar stock which was secured by the muffler straps. The two air gaps created by the shield helped lower the temps.





FWIW,
Sherwood
http://members.rennlist.org/911pcars

[bigchillcar]

nice fixes, guys..metal heat shields or ceramic blankets..pretty cool.
ryan

[buster73]

Fiberglass parts will not melt as some of the newer thermoplastic bumpers (964...), but you can still burn them. Typically you will get bubbling paint first. With higher temperatures the resin (polyester or epoxy) will decompose, leaving just the fiber structure. Though less likely than with thermoplastic bumpers, it is still not impossible to ignite the resin and get a fire. I once burned a hole in a brand new Ruf rear bumper while testing a new exhaust system in a high speed run on the German autobahn - still remember the horrible smell. You need a safe distance to hot parts or some kind of insulation. Coating the inside of the bumper with a high temperature resistant white or silver paint might also help to reduce heat transfer somewhat.

[Bill Verburg]

I wouldn't worry about it, I insulated moine at first but it turned out to be a non issue. pink f/g insulation works also if you must.

[thrown_hammer]

I have glasspacks that touch the rear bumper. No melting or heat issues whatsoever.

[David]

Just put some Thermo-tec adhesive backed heat barrier on it like this http://www.thermotec.com/products/full/13500/13500.html

I put it on my turbo and the FG bumper is much cooler, but still pretty hot. For a NA engine it should work great. You may need to add some additional fasteners, glue, or something at the corners to make sure it stays put.

[adomakin]

i used some nasa type stuff that came in two foot square sheets. trimmed them up and stuck them to the inside of the bumper. worked a treat

Andy

[randywebb]

Thanks - I'll just leave it for now. I'll check it with my hand (assuming the painter ever actually finishes the car). If I feel much heat I'll tape a Tcple up there and move the data logger out of the wine "cellar"... I have some sheet Al if I need to tack something up there.

[Jack Olsen]

The $20 solution works fine and is from J.C. Whitney.

[Edit: Whoops, I meant to post this in the other heat shielding post. Ah, well.]

[tobluforu]

Originally Posted by Jack Olsen

The $20 solution works fine and is from J.C. Whitney.

Agree as that is what I use on my glass bumper as well as many other parts on a few other cars I have.

[TRE Cup]

yep- that's what we use !

[RWebb]

I am cross-linking the 2 threads on this topic for ease of eventual Wiki-ization...

http://forums.pelicanparts.com/porsche-911-technical-forum/408968-heat-sheilding-material.html?posted=1#post3942556

[}{arlequin]

mine's touching my muffler and it's fine.

[}{arlequin]

mine's touching my muffler and it's fine.