I have a rebuilt 355 with about 6000 miles on it. ive had a 180 thermo in it since last spring and last year it ran 180 always. this spring it started running warm (210 w/ 180 thermo). so i replaced the thermo thinking it was sticking, but no success. i seen talk about drilling holes on the thermo... how big of holes, and how many? where (on the flat part i assume)? my changes since last year are new 3.73 gears from 3.23 stock. and i put a 4th gen washer tank in front of the radiator, but i removed it completely and that didnt do any good so i put it back on. i use my auto meter gauge i installed last year so thats not junk i know. what could be my problem/a good possible fix? should i try the holes first, then new cap, then new/better fan(s), then radiator? im still running stock radiator and fan. thanks everyone.

 

https://www.thirdgen.org/forums/v6/6...low-after.html

 

So you're telling me to drill that small hole and I'll be golden? Lol. It's one of my things to do but I haven't had the time lately. Just started a new job Monday and is kicking my ash.