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Most Common Blemishes Found on Body Kits

Fiberglass parts have inherent blemishes from the manufacturing process.

Some of the Most Common Blemish you Find on Fiberglass Parts

(Problem) Pin Holes - When gel coat is sprayed, there are tiny pockets of air trapped inside. When the gel coat dries, it sometimes forms a tiny pocket of air that will remain for the life of the part. Rarely can they be seen. Now when you sand the part to paint, it cuts the surface of the gel goat and walla! A hole on the surface the size of a pin (hence the name pin hole). Picture 1

(The fix) Polyester Primer - Gel coat can be tough to sand sometimes so we recommend cutting in down pretty quick with 80 grit, this will open up all the pin holes. DA sand the flats, hand sand the rest. No really, make sure you sand everywhere… After sanding the surface of the gel coat (without sanding through). Spray 3 - 4 heavy coats of Polyester Primer (Picture 2). This type of primer is extremely high build and will cover even the worst blemishes in gel coat and even fiberglass where the mesh is showing. Allow primer to cure for a couple of days, DA or hand sand as normal. If you find waves in the surface, now is a good time to block, if you decide to block, use 80 grit again to speed things up. You will be re priming with a good 2K primer later anyway. 80 will speed up the process.

After a good coat of poly primer, your pin holes should be gone. After sanding you will need to re prime with a good 2K primer. Polyester Primer cannot be painted over!

(Problem) Blisters - I called them blister (picture 3), only because they show themselves when the parts are heated in the sun. Yes they are air pockets also, just bigger then the ones that turn into pin holes. They are so big, when the panel is warmed, they show as large bumps.

(The Fix) Cut Them Out - Warm the panels in the sun, ideally the hottest part of the day. While the panels are warm (if your brave you can use a heat gun but be careful, you can warp and burn the panel), go out and look for the blisters, you will know they are blisters by pressing firmly on them, if they push in, they are blisters. Using a razor blade, cut out each one you find (picture 4). After you've located and cut out all the blisters, bring the panels back in. When they are cool, using a high quality filler like (Fiber Tech). Finish with the normal fillers and, you will be covering these when you re prime the entire panels.

(Problem) Cracks - Yea you will see cracks, most are cause by stress. When fiberglass parts are released from the mold, they sometimes use air pressure to pop things loose, this air pressure will flex the gel coat and sometimes cause stress cracks. They can sometimes look like spider webbing.

(The Fix) V-Groove - V groove the cracks, easily using a die grinder bit, chuck into a cordless drill. Dremel too with sanding barrel or the like. Either way you want the crack ground down in the shape of a V. The V shaper will allow a smooth transition and feather edge during the repair process. After the cracks are grooved, you can fill using the Fiber Tech (picture 5). Sand as normal (typically 80 grit) and re prime with the 2K when you do the rest of the parts.

(Problem) Bolt Holes to Close to Edge - Sometimes when the parts are removed, they trim off too much material on the ends or the inside of the kit where the bolts are supposed to go. Then when you go to mount the kit and put the bolts in, they are too close to the edge and the bust through. Common problem with cheaper kits.

(The Fix) Building Tabs - AKA, adding material to the area the bolts are supposed to go (picture 6).
We covered this in another article titled “How To Repair Tabs”. See that article for more information. We will be updating the photos for you on that page.

Ok, there you have it, the most common problems you will run into when buying body kits and going through the installation process. We hope it helps you understand when they say “Body Kits are never bolt on”. By definition, bolt on means just go through the install without any fabrication or modification.