Pro Seal (for fuel tanks) is NOT a good firewall sealant! I don't know what temp it's good for, but it's nowhere near 600F, and it burns.
Vans sells a firewall sealant, but it's not cheap and has to be mixed as well (maybe that's the stuff you are talking about). I used it to seal my firewall and all the openings I could at that time. The rest got the Hi-Temp RTV.
Dennis Glaeser CFII
Rochester Hills, MI
RV-7A - Eggenfellner H6, GRT Sport ES, EIS4000, 300XL, SL30, TT Gemini, PMA6000, AK950L, GT320,
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