Originally Posted by
flyspyder55
first off, checking compression while the engine is running is a proven method of diagnostics.... many things in a motor change under load.
heres a good example... youve got a weak headbolt on a boosted car. compression testing the motor at idle may show decent compression numbers, while when its got load on it, it may be stretching the bolt and allowing the HG to leak.
you guys are all so gung ho to hate but experience can come from listening not just doing... and at my age... 24.... i'm gonna go ahead and listen.
So this good example is apparently a car that makes enough boost free revving to lift a head bolt. How many cars make that much boost in neutral?
And just because the motor is running DOES NOT mean it has a load against it.
In reality one of the worst things you can do is rev your engine up with out a load against it.
Hell even GM has figured that out and implemented a measure to keep cars from free revving very high in an attempt to cull things of this nature.
Now if you want to be serious about loading the engine then you need to take your car to a dyno and do testing while the engine is actually loaded.