Strange Brake Problem - Fixed But Still Confused
 

I have a 79 2wd Pickup that up until today had pulsating brakes that locked up with very little pressure. I had exhaust gases escaping into my cooling system so I had my head machined and when I got it back on the road today the brakes don't pulsate anymore! I don't quite understand why it was happening or why it's now fixed but if anyone here can shed some light on it I'd appreciate it.

I like to think I'm a pretty good mechanic but this just doesn't make sense to me.

I know I didn't say it but it has the stock 20r that's been rebuilt, the only aftermarket mods are a carter p4070, GM ignition conversion and a weber 32/36. I doubt it's relevant but I figured I'd put it out there.

Possibly getting compression into intake through intake valve/ blown head gasket causing the vaccum to modulate? That's about all I could think of.

Thanks mwisham I think that's about the only thing that could really make enough sense for me to agree with. When I pulled the other head gasket, it was burnt with exhaust gases between 2 and 3. And both cylinders went from 150psi to about 130-135 so I was definitely losing compression. Maybe the problem was when one cylinder would fire the other ones intake valve was still open and it didn't like that extra compression being forced back through. I don't know if that makes a whole lot of sense but it works in my head haha. I guess I'll just be happy with the fact that I don't need a brake job when I thought I did before.

Also, I wanted to recommend the machine shop I used. I had the head hot tanked, resurfaced, and one of my spark plug holes chased to fix some slight cross threading and they called me only two hours after I dropped it off to have me pick it up. The total was a measly $48.73!!! I couldn't believe not only how quickly the work was done, but also that they didn't charge me for the cleaning or thread repair. So for anyone in Washington state, these guys are called Johnson's Machine, located in Olympia, WA. And I'll be using them from here on out.