I am getting ready to switch out my rear 9.5's to the 11" zr1's. Will the extra size and weight hurt my 1/4 mile times at all?

 

Depends. Do you spin now?

 

I used to spin, but I have worked on my launch and have hit 1.896 for by best 60' with no wheel spin at all. I typically spin just a bit though and hit 1.9's or 2.0.

 

They may help in your case then. Rims/tires are considered unsprung weight. For every 1 pound of unsprung weight you add it is sort of figured to be what ~2.5 pounds of sprung weight would be. The 'ballpark' figure is that 100 pounds of sprung weight will slow you down by 0.1 seconds. If you weigh your new setup and subtract your old ones you should be able to get an approximate.

 

I slowed down quite a bit, couple tenths.

 

That was probably your breakfast.