a 3 angle valve grind on a 360 head will make a lot more flow over a prepped 273 head, the 188 valve does fit, in the bores, last time i flow tested difference was bout 25 cfm per port.
Just should not do it with a low compression 2bbl 273 or you will have a dog. and you must use a 340/360 head gasket or the fire ring will be in the chamber. Even lower compression....
I had a 1965 Dart GT, 273 0.040" over with the TRW piston crown 0.075" above deck.
We bowl worked and ported a set of closed chamber 273 heads and put back cut 1.88 intakes and a back cut 1.50 ex valve in. With a Carter 625 CFM AFB, 340 resto cam, a set of modified 340 A body iron ex manifolds to fit the 883 trans and 3.23 in a 8 3/4 SG.
Did not have the cash to have them flowed back in 1975 but the 'Butt Dyno' said it was quicker. Daily driver till 1985 when I traded it in for a 1984 Shelby Charger in Augusta GA.
I would kick my friends 1984 Z28 5.0L 5 speed's butt all day long. He had headers and was chipped.
