I saw a few questions on this. Since I just did this I figured I would give some of my information on how I did this. I did this exhaust manifold gasket replacement on my 1999 Chevy Blazer 4wd. You should have jack, jack stands, 13,14,15mm sockets. I am lucky enough to have an air compressor. It really helps getting these bolts off. I also have some PB Blaster with both 1/2 and 3/8 drive ratchet, sockets and extensions. Just makes life easier. I jacked the car up and took both front tires off. I also took both inner fenders off. I needed 13mm socket to do this. It makes it way easier to get to the bolts and to see what you are doing. I soaked the bolts with PB Blaster and let it sit. I did a second coat and let the truck run for about 15 minutes. I was able to get all the bolts off on both sides except for two. Both sides had one stubborn bolt on each side. I just soaked them a few more times and started the truck up to get the PB Blaster to soak inside the threads. I was then able to get them off. I used a medium size pry bar to help pull the manifold away from the engine so I had enough room. I put some gasket sealer on the gaskets to help hold them in place. I used a small screwdriver to hold gasket in place through one bolt hole so it stayed lined up. Put bolt in the other hole then removed the screwdriver and put in the other bolt. I only put bolts in enough so gasket stayed flush and would not move. I started at the back and worked my way to the front. Two back, two middle then two front bolts. Once they were in place I made them all snug then torqued them to 22 ft pounds as my manual calls for. Did passenger side then driver side. On driver side I took out battery, battery tray, over flow bucket with inner fender. On driver side I took out air cleaner assembly with inner fender. I hope this helps whoever is on their way of doing this job. You also might need a small flashlight to see that you have the bolt holes lined up correctly. Thanks Bernie11

 

You don't need gaskets on the manifold to head unless you run headers or something is wrong with the cast iron manifolds. Haven't ever ran them on any 60 degree v6, 90 degree v6, or small block chevy and have never had a sealing problem.

Torque them down, let the heat cycle a few times (if not clearly leaking), hand tighten them again. If clearly leaking then go ahead and tighten them and heat cycle. Even with gaskets checking them after a few heat cycles is suggested.


Headers are a different story and DO require gaskets.