A carcass for a self-sealing pneumatic tire is constructed by starting with an extruded thin flat strip of puncture sealant both surfaces of which are detackified. The strip is place on a building drum and its upper surface is wiped clean so that an inner liner may be adhered to it. Thereafter, the carcass is conventionally completed with superimposed successive layers of belts, and tread along with bead rings, etc. The carcass is then cured in a conventional curing press so that the sealant is cured by contact with the curing bladder. The curing sealant is not restrained in any way, but does not flow. Alternatively, a laminate of the sealant is formed with the inner liner, with only the exposed surface of the sealant detackified so that it adheres neither to the building drum nor to the curing bladder. The detackifier remains on the sealant. The recipe for this effective sealant product requires a ratio of high molecular weight elastomer to low molecular weight elastomer greater than 1; also, that there be at least as much, by weight processing aid as there is high mol wt elastomer. Such a recipe has a room temperature peak Mooney viscosity above 70, and, after curing, a peak Mooney viscosity at 150.degree. F. in the range above 15 but below 30. A combination of homogenizer and tackifier facilitates maintaining the necessary viscosity of the uncured sealant recipe. The tire provides excellent self-sealing results.