The Ford Barn

restoross · 02-04-2024, 03:29 PM

Have 53 Merc 8ba 296 cu.in. 3 Holley 94's, dual point Mallory,Edelbrock heads and intake, Stainless steel valves, Howard M12 cam. Has a miss starting at 3400-3500 RPM. Vacuum at idle (850 rpm) 15 in/hg with less than .5 in fluctuation, max steady to 18 in/hg at less than 3400 RPM above that the vacuum gauge goes nuts and sounds like a miss. have subbed carbs, ignition etc. This problem showed up after Cam change and new lifters but with valve springs used with SU1A grind cam that was in the engine when I acquired it, my gut feeling is valve float. My research has come up with using Isky 185G single springs or Isky 4005 dual springs (can dual springs even be used on a flatty)?? What say you Flathead gurus for springs that will work???

M12 specs are intake duration 274, exhaust 277, 53 degree overlap 112 centerline, .360 lift both intake/exhaust.

02-04-2024, 03:29 PM	#1
restoross Junior Member Join Date: Dec 2010 Location: Thompsons Station TN. Posts: 5	Proper Valve springs for 296 cu.in. flathead with Howard cam M12 Have 53 Merc 8ba 296 cu.in. 3 Holley 94's, dual point Mallory,Edelbrock heads and intake, Stainless steel valves, Howard M12 cam. Has a miss starting at 3400-3500 RPM. Vacuum at idle (850 rpm) 15 in/hg with less than .5 in fluctuation, max steady to 18 in/hg at less than 3400 RPM above that the vacuum gauge goes nuts and sounds like a miss. have subbed carbs, ignition etc. This problem showed up after Cam change and new lifters but with valve springs used with SU1A grind cam that was in the engine when I acquired it, my gut feeling is valve float. My research has come up with using Isky 185G single springs or Isky 4005 dual springs (can dual springs even be used on a flatty)?? What say you Flathead gurus for springs that will work??? M12 specs are intake duration 274, exhaust 277, 53 degree overlap 112 centerline, .360 lift both intake/exhaust.