Bubbles in hyd. Clutch

[munice]

Hey all, Well I lost pressure in the clutch again today... I've had this issue before when I first put the 454 in. The problem was that the engine was pulled from a truck with an auto trans, so I had the wrong exhaust manifolds for my application, the guys at the muffler shop were able to route the pipes still just narrowly missing the slave cylinder but as a result the brake fluid in the slave would boil and i'd get air bubbles. So I switched to DOT 4 which is meant for these scenarios and its worked great until last week. Last week it gave out on my way home from work so i slam shifted it home and then bled it the next day... back in business. I figured that time was just a fluke (ie: you're supposed to bleed it once a year to prevent bubbles...) so it worked fine the past few days, and then today on the way home it gave out again.. I suspect it to still be overheating, (as opposed to a cracked up line or anything) because this time and last time seemed to be after a fair amount of driving around during work. I'm just suprised that it got hot enough to boil DOT 4!

I've got a set of early 70s manual trans manifolds that I could put it, only thing is that the dont have an O2 hole, Not sure if there is a way to bypass the O2 ?(rather not drill a hole in nice manifolds (eventually going to carb it so..)

but anywho thats the story, Im just wondering if it is indeed plausible that I just overheated the line again? Ive heat wrapped both the collector and the clutch line to try and isolate the two aswell.