I have a 2006 Nissan Altima 2.5 and have white smoke coming out of the talepipe

SOURCE: how do i know when the valve cover gasket is bad on a1995 nissan?

it would be leaking oil. are you having an issue with your car?

SOURCE: replacement of a head gasket on 2.5 liter nissan altima 2002

frajogag: First off, be aware that these bolts are "torque to yield" bolts (streach bolts). What this means is that instead of torqueing the head bolts to a specific torque specification, they are torqued down to a set spec and then tightened by rotating the bolts a certain angle, like 90 degrees. and all of them are turned the same amount.
This means that the shanks of the bolts must be checked to make sure they are not too thin (or the bolt has already stretched beyond limits and is prone to snap if used)
Here is how you check the bolts. Measure the bolt using a micrometer, at the base, or within the first 13mm from the end where it threads in. Then go to about 10mm before the threads end heading toward the top of the bolt. There should not be more than a 0.23mm (.0091 inch) or less difference or the bolt should be discarded.
Torque the bolts down to 98.1Nm ( 72.ft lb)
Looking at the head from the side, so you are looking at the full length from side to side, I will number the head bolts in this fashion.
#1 & 2 are directly in front of you and in the center of the cylinder head crossing it width wise.
#3&4 are to the left of #1&2, / #5&6 are to the right of #1&2
#7&8 are to the left of #3&4 / #9$10 are to the right of #5&6
Now, you have the sequence.
After the initial pull, back off all the bolts in the same sequence and then retorque them to 36 Nm ( 28 ft lb)
Using a torque angle wrench or having the ability to accurately judge turning angles. Rotate (clockwise) to a 75 degree angle. do this to all the bolts using the sequence I had provided.
Rotate the bolts (clockwise) 75 degrees again on all bolts in the same sequence. The proceedure is complete!

SOURCE: can a 1995 nissan altima head gasket be resurface because I was told it couldn't?

I have resurfaced a 96 altima head with no problem

SOURCE: 2007 Nissan Altima - smoke from tailpipe

It sounds normal white smoke comes from moisture in the air as it's burned and the air temprature is different. it creates steam they gray smoke is a little harder to decide what it is, normally gray smoke is related to oil burning and black is over fuel, depending on how many miles it has on it it could have bad valve guide seals but would not worry about it.

SOURCE: leaking coolant from head gasket area and valve

Well the head gasket job will cover the valve cover gasket ( you have to do one to get to the other) Bring it to a repair shop its about a $1500 job.