Not an aftermarket head-definitely an old STS Engines .28 head as
@slw2206 mentioned above. I’ve ran a BUNCH of STS stuff/mostly 20yrs ago as we knew the guy.. Got in on some ridiculous group buy deals, and had two of the best engine modifiers in the world knocking them out as fast as we could get them to ‘em lol.. Adam Blevins of AB Mods, and ol’ “Supertib” (Neal) of Clockwork Race Engines. I primarily ran the 7-port Turbo head, buggy, race .21’s, but did have a couple modified .30’s, and even the .28’s.. You absolutely could not beat them for the price, and they ran VERY well. Hurt a lot of feelings amongst my diehard Novarossi, and RB Concepts buddies.. Theirs were modified as well..

Not sure on the engine itself, I’m sorry I am not more help bud..
Here’s an AB Mods turbo 7port .21, and AB Mods .30 doing work..
This was about 3/4 gal mark.. I started the break-in the day this was shot. We burned a LOT of fuel back in the day..
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That poor center did.. AB Mods STS no care about 500k

.. Titanium chassis Tazer PRT courtesy of the late Rob Bender of NitroHouse, and our very own
@SoCalTazer . This was taken around 2005.
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