[4birds]

What did GM use between the underhood bracing and the skin to keep the hood skin somewhat rigid? I have a Trans Am hood where this stuff is missing in a few spots. It kinda looks like a type of seam sealer squeezed out of a tube in a sloppy pile.

[78w72]

Cant say what product they used originally, but for the TA hoods Ive had repainted, my paint guy said he uses the 3m window sealer in a tube, think its butyl or some other super strong adhesive. Just make a small blob to resemble the factory stuff & it will cure to hold the brace to hood very well, one of mine has been in use for 15 years with no signs of breaking free.

Can buy the stuff at auto zone or other parts stores.

[400 4spd.]

Use an anti-flutter expanding foam, made specifically for automotive use. It stays pliable and is NOT the same stuff made for home use. I've seen automotive urethane sealer used by others and it will shrink and create dent-like depressions.

[78w72]

15+ years with no shrink or dent like depressions... almost 15 years on a 2nd one with no issues. 3m says it can be used on non structural body panels too.

There are other products for this, but the 3m window weld stuff works great & is easy to find with no negative results in my experience.

[mrennie]

3M 04274 NVH dampening material is the right stuff.

Like other 3M products, it is expensive but great quality.

Requires a special gun for twin tube cartridges that is not cheap. You can make do with a cheaper more common twin tube gun designed for larger cartridges if you use some cardboard as a spacer to hold the smaller tubes in the gun.

[4birds]

That's what I'm looking for. Thanks everyone for the replies!

[MUSLCAH]

SEM makes a 2 part canister ...with a spiral mixing tube called Flutter Foam....just for that application.

It’s expansion It limited....and doesn’t cause warping