mounting a glass hood scoop on a steel hood

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burrpenick

'69 Barracuda
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I know many say they always crack if glassed on a steel hood, but what about riveting- is there a method where the rivet head could be countersunk and covered?
 
The cracking problem probably has to do with the different rates of expansion and contraction under heat and cold cycling of steel sheetmetal vs the fiberglass scoop. What can possibly bridge that gap between those rates is using JB weld to bond and rivet the scoop in place. This should help bridge that rate of expansion, then use an autobody filler such as dyna glass over the JB weld glue joint.
 
I pop riveted a six pack scoop on to my steel hood.
I then fiberglassed things smooth.
I fine tuned with some body fill and had it painted.
Has been about 4 years. No cracking as of yet.

Mine is functional. I also braced the underside hoping to take out some flex.
 
Mine had the studs already in the scoop.
I sealed it around with a soft door edge mouldings.
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why not go the Ma Mopar route and put studs in the scoop and bolt that baby on - no crack problem there...
 
I put an aftermarket dart sport scoop on my kids 69 barracuda hood. The stud holes in this scoop were dpot on for the factory access holes in the structural web underneath. It's going to stay a bolt on setup. Not moulding it in. You can get fiberglass bolt on hoods from stinger fiberglass with a six pack scoop already moulded in.

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Last year I added a fiberglass scoop to a metal hood with pop rivets about every 2 1/2” then used Bondo to mould it in. The rivets aren’t perfectly lined up because I tried to hide them on the bottom side of the hood.
Used this method back in the 80’s on a different hood and it held up great.
However you mount it, make sure it will not flex.
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What also helps is when you rivet it on, to use backup washers under the rivet rails to reinforce the mounting. This means you need somebody to help you by holding the washers in place while you pull the rivets, but makes the attachment a bit stronger than just using the hood sheetmetal.
 
If you ever want to get perfect spacing for rivets it's a simple math equation. Total length from point A to point B in a straight line divided by the number of total spaces you want between the rivets. This will give you the rivet on center spacing in decimal form. I use it all the time doing sheetmetal patches on aircraft.
 
1976 to 78 I had a Camaro. I put an L88 scoop on it with fiberglass. Never had a problem. It was functional so a lotta heat was not trapped under the hood.
 
My 76 Dart Sport Got its fiberglass scoop put in in 78-9 by a good body shop owner. He put about 3/4'' of body filler and sunk in the scoop. The first crack appeared about 4 years ago. It never moved!!!
 
I know many say they always crack if glassed on a steel hood, but what about riveting- is there a method where the rivet head could be countersunk and covered?
Sure, you can use 100° countersink pop rivets, and countersink em slightly below the top surface of the scoop, then skim body filler or dynaglass over them, but it will eventually crack around the rivets because the heating and cooling rates of the parts are different. The composites and glues of today are definitely better than 50 years ago, so it may last longer than this type of job used to last.
 
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