OzFab
Well-known member
Time for a quick physics lesson...
Inside an internal combustion engine, everything gets hot due to the constant explasions taking place; however, gasoline is cold so, as it passes by the inlet valve, it tends to keep the valve somewhat cool, reducing expansion...
On the other hand, exhaust gasses are hot, which tend to heat up the exhaust valve, causing more expansion...
This expansion (or lack there of) transfers to the valve stem, closing the lash gap between the valve stem & the rocker...
For this reason, the cold lash gap on the exhaust valve is usually significantly larger than the cold lash gap on the inlet valve...
It can be argued that the expansion of the valve head in the seat will take up some of the expansion of the valve stem but, 100 years of engineering R&D can't be that wrong...
Inside an internal combustion engine, everything gets hot due to the constant explasions taking place; however, gasoline is cold so, as it passes by the inlet valve, it tends to keep the valve somewhat cool, reducing expansion...
On the other hand, exhaust gasses are hot, which tend to heat up the exhaust valve, causing more expansion...
This expansion (or lack there of) transfers to the valve stem, closing the lash gap between the valve stem & the rocker...
For this reason, the cold lash gap on the exhaust valve is usually significantly larger than the cold lash gap on the inlet valve...
It can be argued that the expansion of the valve head in the seat will take up some of the expansion of the valve stem but, 100 years of engineering R&D can't be that wrong...