I ant to test if my car is breaking up up top at around 6000 rpm's with out load. Can i slowly rev the engine to 6200 rpms in park or do i risk breaking someting?

 

Yes you can but it won't be the same as under load as the pressure in the cylinders under load "tax" the ignition system.

 

Free reving = bad, I wouldn't do it.

 

Exactly. That and as mentioned earlier it will tell you nothing about what it is doing under load.

 

Why?

I will say the only engine that blew up on my dyno was one that was free revved to 6000+ to check timing at the owners instructions. It did have a season of circle track racing on it too. But I don't like to free rev over 3000, maybe blip it to 4500 but that's the max.

But why would it be bad? If it is a con rod load issue, the con rods are unloaded every other stroke anyway. Is a harmonics issue or a high vibration critical RPM issue?

Why isn't free revving a problem on a Spintron?

 

but doing it should tell me if its a vale train issue.

 

Not wise to rev the engine that high for no apparent reason without a load.
For the same reason you should not "dry fire" a compound bow. Things tend to let go.

Not saying you cant do it small bursts, but your taking a chance.

 

Because there isn't any load on the engine.

 

Hmm... What about all those cars out at the track that are dumping the clutch??

 

They already know your gonna break something when you race, part of the deal. Iv seen people do 10k clutch dumps, that dont mean it will not hurt it.

 

Exactly why is free revving with no load on the engine bad?

 

It wastes gas.

You will be very tempted to drop it into drive @ the rev limiter. That wastes drivelines. Most automatic FWD cars won't let the engine rev very high when it's not in gear just to protect the driveline.

 

I've owned several AT FWD cars, worked on dozens more, and driven hundreds and never experienced or even heard of such a thing. Any cars in particular that this holds true for?

 

My parents 01 v6 mustang has a rev limiter around 4k in neutral, same thing with their 04 ram.

 

All the rental cars i had, had it