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Then How come solid lifters clatter when cold and quiet down when hot? Everything expands and the lash gets tighter.
What? How do the heads and block GROWING with heat close up the lash?
If you can ever get to a track again (super cross starts Sunday and hopefully the NHRA is sick of this and will get going soon) and you get the chance to see some blown alcohol stuff, get a look at them warming up.
Of course, this is an extreme example of what we are discussing, but it’s much easier to see with the naked eye.
Watch them crack one off when it’s at ambient temperature. And pay attention to the blower belt. When it lights, that belt will whip and thrash and will be so loose you’ll think it’s going to fall off. They are very loose cold.
Then keep watching close, and you’ll see the belt start getting tighter and tighter, just with warm up heat. They get much tighter on a run under load.
You’ll see that belt go from thrashing around to being pretty tight, again, with no load and warm up heat.
The exact same thing happens with pushrod length as it does with the blower drive belt. The pushrods grow, but not like the block and heads. The intake and exhaust valves grow, but not as much as the block and heads.
The more aluminum in the engine, the more it grows. The more heat in the engine (or any part for that matter) the more it grows.
So cold lash should be tighter. By how much depends on what you are running.
