I ran lean on cylinder number 4 with nitrous. The spark plug's insulator was half gone and the ground strap was melted off. I did a compression test today on all cylinders and I don't have any previous result to compare it to.

205 205 205
190 180 190

180psi is the one that I ran lean on.

Is difference of 15-25 psi between the front bank and rear bank something to worry about? Maybe a blown head gasket?

 

I think the spec is like 160 psi so I think you're just fine and dandy with 180 psi. You may have just aged the engine a few 10k miles or so but I don't think that's anything to worry about.

 

Standard is 185psi
Min is 145 psi.

I don't remember the different between the cylinders suppose to be. I thought I read 19psi. My cylinder #4 took some major abuse. Screw using mobil 1 now. I'm back to using dino oil on this motor. It's got 67K miles on it. Time to beat the crap out of it and save up for a built motor.

 

turbo

 

205 is probably coming from Carbon Build up somewhere, you shouldnt have compression that high. Brand new and broken in motors is basically at 185psi.

Dixit

 

Some guys have compression in the 200's on new motors. Maybe its the guage, but more than 1 person has found that. Both of my motors have been around 175-180.


Off the top of my head I want to say that the max difference between cylinders should be 7psi, but I'm not 100% sure. I know its in the FSM. However, I really don't think you'll have problems with a 10psi difference. Hell, I drove motor #1 with a 75psi difference for months with no big problems.

 

Max difference between cylinders is 14psi.

 

Any suggestion as to what I should do about carbon build up?

 

Fuel system cleaner maybe?

 

You might want to use the product call SeaFoam. They have an engine cleaner in liquid form that's supposed to clean out your intake manifold/combustion chambers of carbon. I used the spray version but I don't think that was the right way.
http://forums.maxima.org/showthread....hlight=seafoam

 

Doesn't driving real hard on the highway clear up carbon buildup? If so, lend me your car and I'll take care of it

DW