TrickFlow intakes. Not what guys want to see
PA66 (nylon 6/6) is $2.00 per kilo raw granules. The AFR intake weighs 7 lbs, a little over 3 kilos. So 6 bucks in raw materials minus the threaded inserts and water passages. Still pretty cheap and gar less energy to produce and less EPA regs. They do require an 210 C oven dryer but that is gar less to operate than an electric or gas smelter.
Now add glass (or other filler), flow modifier, impact modifier, heat-resistant additives... that $2 per kilo turns into more in a hurry. Yes, it will still be cheaper than aluminum by weight, but not once you amortize the tooling over the anemic demand for Mopar parts. Those threaded inserts are cheap if brass, but none of the ones on the market have worked well for me. I've had to go custom in all instances, and they can run $2-4 each in stainless, and that was several years ago, and they were #10 threads. Larger custom stainless inserts will undoubtedly cost more. Then there's the labor (or cost for a robot) to place them in the tooling.
Trying to tool the ports in an automatic tool would be extremely difficult, and you'll still wind up with some ugly parting lines in the plenum, if not some flash since the shutoffs won't be perpendicular to the closing plane. Hydraulic slides can bear harder, but only so much before the cores snap or crack due to the torque (since they're not straight). Especially once the tool warms up.
Again, nothing about it is impossible - it's just not well suited technologically for this application. Between all the oil and heat on the bottom of the manifold, fuel through the intake (which will embrittle the polymer over time, no doubt), thin bolt flanges that are too close to the ports (crack city), and the temperature differential of the part due to the thermostat housing... it's a recipe for disaster.
Run a separate water neck, block off the rear coolant ports, use heads w/o a heat crossover, and then use port injection with the bungs in the heads, and a valley plate - it could work. A BB intake would probably work well in polymer, in fact. But there's still an issue with volume to pay off the development of the tooling. Without an OEM behind it, I just don't see it making any financial sense.
I could draw up a manifold that could be v-process cast without any special requirements that would cost as little as $20k, in comparison.
