727 question

Ok my set up is a 66 727 with a Cheeta Action full manual reverse pattern valvebody with a Cheeta Action torque converter. Last time I drove it I was on the expressway going about 60 mph for a while, i'm running a 4:56 rear gear. Engine temp was good @185. It started smoking out the back. I stopped and looked under the car. No drips that i could see. Wasn't smoking while stopped. Got it home pretty quick. Checked it out and it seems like it was leaking somewhere from the front pump area. I put a new FP seal in a couple of months ago.
Could the fluid pressure build up and blow out the vent?
I'm thinking about installing a temp guage to monitor it.
Any ideas on why it would leak so much to blow out from the inspection cover area and burn off on the headers?

I have had issues with leaks from the front vent at high RPM. I taped the vent and plugged it, and installed a vent at the rear of the case.

Ok. Great. At least it's happened to somebody else.
How did you install a vent in the rear of the housing?
What did you use?

Thanks for the info