I needed the larger combustion chambers of the 340/360 heads with those pistons as with the stock 318 heads the compression was too high and was causing a pre-ignition flame front over 80° F and the engine would over heat within 20 minutes with that much compression... It idled at 24" vacuum with the 318 heads and dropped to 22.5" vacuum with the 360 heads...
With the larger heads that combo ran 400,000 miles on my daily driver on that engine... I used 1.88" intakes for the first build, then went to 2.02" valves after the second refresh... No problem with either valve combo...
