Video: DIY Plastic Welding to Shave an LS Truck Manifold

Our favorite do-it-yourselfer, YouTuber AGearhead4Life, is back with a new video that demonstrates how anyone with a soldering iron and a bit of patience can modify factory GM thermoplastic intake manifolds. In this video, he takes a stock truck manifold and “shaves” it to smooth the top and relocate all the vacuum and sensor ports to the rear of the manifold.

The wood screw provides a handle to let you hold the filler piece in position while you initially tack-weld it to the manifold.

The process starts with removal of all the unwanted pieces, using a reciprocating saw to cut off the larger bits, followed by some preliminary sanding. The extra pieces are saved, though – the big chunks will fill the holes left by removing the ports, while the smaller pieces are used as filler material. An ordinary 45 Watt soldering iron with a broad tip is used to melt the plastic and nudge it into place, looking like the world’s least-tasty cake frosting.

The work continues once the holes are filled, with the factory port connectors relocated and welded to the back of the manifold, then everything gets sanded, hit with a layer of body filler to take care of the minor imperfections left over, then painted satin black. The end result is a much nicer-looking intake manifold that is still completely functional and compatible with the stock engine.

The manifold before and after modification.

This technique isn’t just useful for looks – ambitious garage hot rodders could use it to modify stock intake manifolds for performance reasons, or to repair a manifold damaged by a backfire. We’re sure there are more than a few of you out there with truck manifolds sitting around, so start practicing now!

About the author

Paul Huizenga

After some close calls on the street in his late teens and early twenties, Paul Huizenga discovered organized drag racing and never looked back, becoming a SFI-Certified tech inspector and avid bracket racer. Formerly the editor of OverRev and Race Pages magazines, Huizenga set out on his own in 2009 to become a freelance writer and editor.
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