Do this test with the engine off and cool. Get a two-foot length of 5/8 ID hose. (If you buy PVC hose, you can use it later, in conjunction with a three-inch section of 5/8 OD copper pipe from a plumbing store or building site, to relocate the flame trap if you want.) Pull the flame trap assembly off the breather box, and push the new hose over the nipple on the breather box. Take off the oil filler cap and try to blow by mouth through the hose that you just connected to the breather box. With a new or super clean breather box, you'll be able to easily blow through it. The easier you can blow through it, the easier your crankcase will breathe. Your breath will come out the oil filler cap hole in the valve cover. This test just checks the breather box. Also, check all the hoses and fittings downstream (above) the breather box, and clean or replace any part that is sludged up or clogged. This includes the brass fitting in the manifold where the little hose connects. Often people, including the professional foreign-car mechanic that serviced my car for 10 years before I bought it, fail to check the breather box. If it's clogged, a new flame trap with attached hoses and fittings won't do any good whatsoever. Mine breather box was totally clogged so I replaced it, although some people do clean the dirty old boxes out. Whatever you do, let it breathe.
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock; 86 240, 129K