Breather to breather is 1/8 pipe by 3/16 hose. Down pipe 1/8 pipe by 1/4 hose. I plan at some point to make the down pipe 1/8 pipe by 1/4 ss pipe. 3/16 hose may seem small but if you look at the actual hole size in the breather bolts they are really small. Less than 3/16.

 

Ok thanx.

 

I used a drill press and new bit... it was pretty easy, cut like butter... but I still went slow...

 

This is so true, I measured the my stock breather bolt's hole to be a 3/32" in each (at I believe the head end), and that was the most "restrictive" point in the stock setup. So figuring down stream of that , where the 2 lines joined if you double the 3/32"s hole to 6/32" (3/16") hose, it actually has almost 4 times the "capacity" of the 3/32' hole in the breather bolt. Of course inside diameter of the hose fittings used will be smaller and their actual ID is what would be important...

I know the formula for figuring volume/capacities of different diameters of holes/hoses, but after running the numbers I had a hard time believing that going from 3/32" dia. to 6/32" (3/16") dia. it had almost 4 times the volume/capacity... I had to be able to see it for it to make sense to me, so I did a quick drawing.

 

Breather to breather fittings are 45 degree. Found them on eBay.
​​​​​​