I had installed a rebuilt blackwater long block about 120K ago. at about 30K i had a leaking head gasket and installed new along with fire wire? not fire rings along with arp studs. I have easy edge and rv injectors and 4inch straight all in a 99 club cab dually 2 wheel drive,6 spd. My problem started after i had a friend drive a load for me, I have a pyro guage and light on guage is inop. so advised him not to run her over 1000 and check guage at night in the hills with a light etc. My guess is he ran it up and possibly caused my now blowby. What temp is safe? Could i have a head gasket failure causing the blowby? I understand weak rings or score does cause blowby but wonder if a head gasket could also cause this from possible head heat. Since this issue i also notice under load up hills running no more than 1000 on the pyro i notice my coolant temp rises as it never has done that before.

1250*F is what is considered safe. I typically hold at about 1,200*F. My limit on the Quadzilla is set at 1,300*F.

 

All I can say is time for a compression test and find out what cylinders are damaged. Then you'll most likely pull the engine out to be rebuilt or those cylinders repaired. 

Thank You

Leak down would be a better indication imo than a compression test.