Going 70-80 mph in third gear probably floated the valves. Nice.


Do a compression check. And a compression loss check.

 

Coolant injection from a cracked head will cause that.

 

If I'm not mistaken, this is what was suggested to me to try. And I didn't go over 75. And also, it was only at this speed in that gear for around 1 minute. I know you know your stuff but don't knock me for trying something that was suggested by another forum member.

 

CORRECTION: It was actually YOU who suggested it to begin with. And I never even reached 3200. Just 3000. So why tell me to do something then knock me for doing it?

 

...................

 

Sorry for jumping the gun on you but when I do mine I only drive at around 40-45 mph.

 

I hold mine at 3500 RPM for 3 minutes in my driveway. Ain't skeered.

 

lol

 

True story. Done it for years on different 4.0s. They're all still running at about 200K......

 

OK well don't know why the speed would be different other than the gearing is different. I was under the impression that you had to have the engine under "load" (driving) for this to work right. I can try what cruiser said and just do it in the driveway not moving.

 

Make sure it's up to temp first. Don't do that on a cold engine.

 

After doing all Cruiser's mods, I take mine up to 4k every now and then getting on the freeway( 3rd gear, 4.55's) Cruiser told me not to be skeered.

 

And you're not, are you? LOL.