I have a set of Speedmaster SBM heads in the shop for a lookover.
All they wanted done was to make sure they were serviceable...... they’re not here for any performance enhancements.
These are assembled heads, part number PCE281.2146, set up for flat tappet cams.
They came with dual springs w/o damper, 10* retainers & locks, and steel jacketed seals.
I pulled them apart, checked the spring installed height, guide clearance, and valve seat run out.
Seats were not machined in a way that benefits air flow, but the concentricity was good, and the guides were all about .0022” clearance.
The only “issues” that could have caused some headaches had they been bolted on “ootb”, was two of the springs were down about 15lbs seat pressure, and most of the seals fit poorly(quite loose) on the guides.
Even though the springs are duals, the rate is fairly low.
125 on the seat, about [email protected] lift.
They have quite a bit of travel though, so I just shimmed the two that were low up to 125lbs.
I also replaced the seals, which fit nice and tight...... so the poor fit was in the seals, not that the tops of the guides were sized incorrectly.
Plopped one on the bench, “just to see”.
4.00” bore, 28” test pressure, no tube on exhaust:
Lift——in/ex
.100— 60.4/48.8
.200—120.4/97.6
.300—176.8/134.2
.400—221.4/153.7
.450—230.7/159.8
.500—240.1/164.7
.550—250.5/166.4
.600—250.5/168.3
.650—251.3/168.3
.700—253.1/168.3
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