As of 6-30-20 we have five pairs of these bare castings in-stock and ready for finish work with our high quality components and craftsmanship. When current supplies are gone we do not know when they’ll be available again. That doesn’t mean they won’t be available, just that we don’t know. There have been large gaps in availability in the past.
Base price for a pair fully assembled with studs and ready to go with ceramic thermal insulation coated combustion chambers, valve tops, exhaust valve back sides (tulips) and full length of exhaust ports is $1715.00.
44 x 38mm S.S. valves
Crower HD single valve springs. Chromoly retainers.
Fly-cut to customer chamber volume specs, within certain volume limits.
Intake ports port-matched to O.E. 3 Stud F.I. intake manifold insulator gasket
Options are available.
Heat is the enemy of all air-cooled heads.
For additional heat protection the black exterior heat conducting coating is amazing. Our coater will not tell us what it is, but it’s a highly durable Teflon-like material. We’ve been using this coating for about 15 years now and have been very impressed with its ability to disperse heat rapidly lower head temps over uncoated heads. We have also observed on coated race heads that have come back to us for freshening that the fins do not have the typical coating of dust and oil and soot that accumulates on all air-cooled heads over time. This layer of soot acts like an insulator that inhibits the heads heat shedding ability. This feature of the slippery coating makes it worth the price alone, in my opinion. While I am a big fan of the exterior coating, if the budget will only cover one coating go with the ceramic. For extreme use like track cars and heavily loaded Vans, especially those operating in extremely high ambient temperatures the two coatings combined offer as much insurance against heat related damage as I have found to date. The black coating adds $290.00/pair.
These heads produced by AAPistons are knockoffs of the 039 101 371A heads that came on pre-smog 2.0 914/4’s. They are often referred to as 3 stud heads due to the fact that they feature 3 intake manifold studs, unlike all other Type4 heads which have 4 studs.
We purchased our first pair back in 2017. They had a grab bag of minor imperfections, but overall weren’t bad. Subsequent casting runs have seen solid improvements. As of July 2019 the latest batch has addressed most of these issues. We address the rest with our attention to detail
2017-2018 we prepped fifteen pairs of these heads. Every pair received thermal coatings to the combustion chambers and exhaust ports. So far we have heard nothing but positive feedback on performance and reliability. But the sample size is small and not a lot of time has passed. I will say that one of our customers has been using a pair with excellent results on his heads on a 914 prepped for Chumpcar endurance racing. His feedback has added to my confidence.
As knockoffs go, overall they make a pretty good visual first impression. There are some exterior details that aren’t as exquisite as the German originals, but that’s no surprise and not particularly alarming. The first thing that jumps out is that AA dispensed with the 15mm O.D. exhaust guides, opting instead for the 12mm size used on the intakes. This sits well with me, but does eliminate the option to run 9mm exhaust valve stems. Something we haven’t done for years on any but our transporter heads, so no problem there.
After a thorough visual inspection we mounted them in our CNC machine for some reverse engineering to see how they compared to our programmed specs for factory heads. Overall I was pleased with those results as valve guide bore centers and register centers as well as chamber floor heights were all spot on.
Once we were done reverse engineering, we CNC machined valve seat counter-bores using the same feeds and speeds with the same tooling as we use on AMC heads. The chips and machined surfaces were identical in appearance to the AMC heads and the machined dimensions were within .0002″ of what we get with the AMC’s. That tells me that they at least have similar machinability, which is encouraging regarding alloy characteristics, but hardly conclusive in predicting durability.
As for the critical features, the chambers are perfect repops and chamber volumes after our finish work measured at 58cc’s, about average for an uncut O.E. head, and were all within .5cc’s of each other, which is nicely within tolerance. The AA supplied fly-cut surface finish is fair, but a random check of the heights from chamber to chamber varied by .0025”, which is way out of spec. Our finish work is within .0001″.
The exhaust ports are pretty much dead nuts copies of the O.E. heads but with a rough texture. After polishing and blending, flow testing results were nearly identical to an untouched German port and respond nicely to our bespoke performance valve seat profile, provided good flow balance for oversize intake valves.