Well I had to leave the Bluesmobile (88 Caprice) up in Bangor last month when it broke down. I went back and towed it home last weekend. It's got a 305 of unknown origin. It's got a bad misfire that makes the whole car shudder. I had to increase the idle screw to keep it from stalling. When it's idling it sounds like one or more cylinders is blowing back through the carburetor. The power brakes don't work at low speed because It pressurizes the intake and eliminates any manifold vacum. I took off the rocker covers and all the pushrods are pushing and the rockers are rocking. There is a slight ticking from the left bank but I can't pinpoint it without a stethoscope.
I'm thinking that I have a bad intake valve that's letting the compression back into the intake but wouldn't that make it backfire through the carb? I should check the compression but my compression tester dissapeared. Maybe I loaned it out and forgot. Any suggestions would be appreciated.

But that's not why I started this thread.

I originally rebuilt a 79 305 to put into this car but the oil poured out the back when I got it running so I took it back out and put in the used engine that only lasted a couple of months. I think it would be easier to fix the oil leak than to repair the mystery 305. I pulled the oil pan and rear main cap off the rebuilt engine and the seal seems ok. I don't want to pull the crank to replace the seal if I don't have to.

So here's the point of this post.

Should I have put permatex on the rear seal where the two halves meet? I'm pretty sure this is where the oil is getting through. Or is there some secret to installing a rear seal that I should know about?