R barrels on SP heads takes 0.2 mm off the squish and takes it closer to not being OK on normal pump fuel.

It works, but you need to be aware you're nearer the edge, weather conditions are more critical, setup is more sensitve.

Double/triple/quadruple check the DECK HEIGHT, as well as the letter on the side, should be 86.3mm for an R ("H") barrel.

You wouldn't be the first to fall for the old "deck height machineing at replating causes seizure" trick
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