Every time the topic of plastic intakes comes up I have to laugh about my own experience with them. Back in 2017 I bought a large 3D printer, with the idea that at some point I could print a plastic intake and test it on the dyno. I had purchased a spool of PLA plastic printing filament and soaked it in ethanol fuel and race gas, and it held up well for a week, so I bought the printer knowing that at least the fuel wasn't going to melt the plastic. When I finally got around to doing my cylinder heads a few years later, I started designing and printing intakes for them.
After printing a sheet metal style intake, I put it on my dyno mule and tried to run it. It was fitted with two big Dominator carbs. To this day I regret not having a camera in the dyno room to video the results. When I tried to start the engine at an idle it wouldn't catch, probably (I thought) because of the big plenum in the intake. So I pumped the throttle a few times, opened it up a little, and hit the starter. After a couple cranks there was a huge, loud explosion and fireball! The carbs ended up hanging over the left valve cover, on fire. The plastic in the manifold was blown all over the dyno room, totally shredded. If I'd had a camera running, I'd have a million hits on youtube with that video; the explosion was absolutely spectacular!
Red plastic from the intake was blown all through the induction system too. I had to pull the heads, and pick little bits of plastic out from between the pistons and the top ring on a bunch of cylinders. Five years later I was still finding little bits of red plastic in the corners of the dyno room from that explosion.
Being a sucker for punishment, I printed another intake, this time a low 4V intake. After it was printed I checked to make sure it was airtight. It was NOT; water poured into the intake would leak out between the layers of the 3D printed plastic. Obviously, my first intake had a huge vacuum leak that caused the problem.
I took the new intake and coated it on the outside with garage floor epoxy to seal it up. Then after getting the engine back together I tried again, and this time the engine ran great with the 3D printed plastic intake. Over the next couple years I kept printing and testing intakes; it only cost about $200 in plastic to print them, and I could make changes to the design on the computer, so it turned out to be the great development tool that I had originally envisioned. In fact, the 8V tunnel wedge style intake went through three revisions in plastic. The first one made only 825 HP, but the third one, which was an improved design, made 875. I was really pleased with how easy it was to tweak the manifolds on the computer, and then get real life data from the dyno which showed any improvements. I was able to tweak all the manifolds for my cylinder head package to optimize their performance.
I did have one other minor explosion along the way, with another sheet metal style intake. Despite being epoxy coated, it gave a small backfire that knocked a hole in the plenum. That huge plenum was just a bomb waiting to go off when you added fuel. Fortunately, that one was no problem to clean up.
Occasionally I get folks who want to buy a plastic intake from me, and run it on the street. I won't sell them one; a single backfire will damage the intake and potentially spread shrapnel through the engine. I think even a modern automotive plastic intake would be a big risk to run on a performance engine, unless it was EFI and the timing and throttle settings were dialed in perfectly. That is how the major manufacturers get away with plastic intakes; best for folks like us to stick with aluminum.
Topic: End of the Line for FE Power Cast Aluminum Products (Read 1858 times)