It depends on the spring force.
If your engine can spin out to 11,500, like the Tornado, the spring force is 1000 N, and that is enough to dent the shims. If the shims develop dents from the valve stems, then the gaps will grow. If you set the gaps tight, they will grow into spec and work harden as they do, slowing the rate of dent depth to virtually nothing over 5000 km
If, like the 1130 Trek/TNT, the engine is redlined at ~10,000, the valve springs will be a deal weaker and the shims won't dent. Then you simply have wear on the seats to deal with, in which case the gaps will diminish
The other, more worrying issue, is if the exhaust gaps increase, it could be due to buildup on the valve stem that limits its ability to close. You then get carbon buildup on the seats which tend to leak after a while, and eventually a piece of carbon breaks off and you have no compression. This is generally caused by oil additives, and the solution is to use a fully synthetic oil (as recommended) which has few additives.
If your engine can spin out to 11,500, like the Tornado, the spring force is 1000 N, and that is enough to dent the shims. If the shims develop dents from the valve stems, then the gaps will grow. If you set the gaps tight, they will grow into spec and work harden as they do, slowing the rate of dent depth to virtually nothing over 5000 km
If, like the 1130 Trek/TNT, the engine is redlined at ~10,000, the valve springs will be a deal weaker and the shims won't dent. Then you simply have wear on the seats to deal with, in which case the gaps will diminish
The other, more worrying issue, is if the exhaust gaps increase, it could be due to buildup on the valve stem that limits its ability to close. You then get carbon buildup on the seats which tend to leak after a while, and eventually a piece of carbon breaks off and you have no compression. This is generally caused by oil additives, and the solution is to use a fully synthetic oil (as recommended) which has few additives.
