I'm tearing down a B20 carb head that I got some time ago from Ebay. Reportedly was rebuilt and then stuck on a shelf. Wasn't painted so it has surface rust. I'm going to try out the Evapo-Rust. If it doesn't work I'll just have it hot tanked.

Looks pretty decent, at least it has a new rocker assembly and valves. Anyway I think it will be OK, but have a couple of thoughts.

There is some light pitting on the intake/exhaust mating surface. Does this need to be machine perfect for a good seal? I could always have it touched by a machine shop.

The block mating surface is nearly perfect. But same question; how perfect is enough?

Lastly; now that I have the valves out I have my first look&feel of volvo B20 exhaust shape. Feel a ridge as it transitions from the seat/bowl to the runner on the short side and thought it might be OK to smooth this out so its more of a radius.

Anyone out there tried to "help" exhaust flow? Seems like it would increase efficiency.

I'm using David Vizard's "Tuning the A-series Engine" as a basic reference. Yes, not Volvo but the design is pretty similar and there is a lot of theory that applies to most internal combustion engines. He goes into great detail, I'm just trying to help when I can and leave well enough alone mostly.

This really just comes down to "while I'm there..." type of thinking. So while I've got the head torn down no better time to do this. I'll be fine leaving it alone, I know the car will run. But I'm also trying to be less cautious about mod's and this seems pretty safe as long as I don't start trying to redesign the chambers or anything. Pocket porting I think its called.

Any thoughts appreciated.

Also, I would be happy to add a couple of pix of what I'm talking about but not sure how to do so on the Brickboard. On other forums or Ebay a little applet does most of the work. Any help with this also appreciated.

Thanks,

Mario E.
Lawrence, KS