First time I did it... probably 6 hours to take the old one off, 1/2 hour to scrape old gasket and clean everything up, and about 2 hours to put the new one on and reconnect everything. It took two days but only because the auto parts store was closed and I had to replace some rotted out vacuum house that took a dump on me.
if everything goes smoothly with the swap it wont take more than an afternoon. however i wish everything went smoothly. i swapped my intake and injectors. i broke both front lower intake bolts in the head and got to have loads of fun drilling them out in the car. i found a pretty trick way to keep any debris from the lifter valley is to get a piece of cardboard and cut it to fit in the lifter valley, then scrape the gasket material off. all i can say is if your intake has never been off and the car has a lot of miles on it, dont be suprised if a lower manifold decides to snap. i was lucky enough to have 2 break
I just did this last weekend and it took us about 30 hours total...This included driving around to pick up the random pieces that were needed along the way. The best advice I could give you would be to do a VERY GOOD job of preparation. I would go get some new o-rings and caps for your injectors because you will inevitably need them at some point during the swap. LABEL EVERYTHING! Take all the nuts and bolts and put them in individual baggies labeled. You're going to want to label all of the connections as well. You may want to invest in some new intake bolts as well as they will break easily at this point. Good luck!
Well it went pretty well... Bud showed up at 9 and we were completely done at 5... but that includes running out for the gaskets and a bolt... so we really got started about 10:30... had it all down to the heads and cleaned by 12:30 (lunch),
Got started again at 2:00... worked for a couple hours till we were basically done, played with my son for a while, made an EGR blockoff plate (SS is a PITA to work with) and had to change a couple o-rings on the injectors after it was said and done..
So all told we probably had 4.5 hours in it...
It seems to run pretty strong... computer is still learning... I'll know more what it did for me in a couple days when the weather dries up... but so far two thumbs up...