Petrobond? Don't know that one.
the kit is made by Dan McEachern,
[email protected] 510-532-8228
Yesteday I took the original rear seal holder, added a little tape and used it for a sand casting pattern.
I made 3 castings one of which I considered to be useable.
I use scrap aluminium, preferably things that have been machined, billitt things ( don't like them anyway) sometimes using previously cast bits machine " gummy" Also I get the molds all sorted before heating the metal, if the metal is molten too long it gets more gas in it making for porous castings.
I am neither a machinist nor a foundry guy, just mess around and stumble through as best I can. I'm sure many here know more and better than I.