LIM gasket post-mortem
 

I'm posting pictures of the Lower Manifold Gaskets I replaced (with the good Fel-Pro ones). I did this as a preventative measure. I thought people might like seeing what 135,000 mile, 18 y.o. LIM gaskets looked like.

What I noticed was for the water passages a buckling of the upper and lower parts with a separation from the bead. There is no similar distortion for the intakes.

The post-it in the picture has an arrow pointing forward. Top and bottom in the file name refer to the top and bottom faces of the gasket; "top" faces away from the cylinder head and "bottom" faces towards it.

https://cimg2.ibsrv.net/gimg/blazerf...342f658e26.jpg
Bottom both


https://cimg5.ibsrv.net/gimg/blazerf...e88746705c.jpg
Bottom right front


https://cimg6.ibsrv.net/gimg/blazerf...79bf46f00b.jpg
Bottom right rear


https://cimg3.ibsrv.net/gimg/blazerf...188197bd4a.jpg
Bottom left front


https://cimg4.ibsrv.net/gimg/blazerf...693e1e9f10.jpg
Bottom left rear


https://cimg7.ibsrv.net/gimg/blazerf...c16d7ca16b.jpg
top both


https://cimg0.ibsrv.net/gimg/blazerf...6063916103.jpg
top right front


https://cimg1.ibsrv.net/gimg/blazerf...3f182d5a6f.jpg
top right rear


https://cimg9.ibsrv.net/gimg/blazerf...e673d2bc90.jpg
top left front


https://cimg1.ibsrv.net/gimg/blazerf...e8e50af316.jpg
top left rear

Nice , I just bought 2 sets so I can do my Jimmy and my Astro van...did you replace the bolts also or just clean and seal the old ones ? , I didn't bother getting bolts.

Whats your opinion on replacing the fuel pressure regulator ? , I have seen a few times that by coincidence the regulator screws up a little while after doing the intake so the upper gets to come off again to replace it .... I'm on the fence whether I should order a couple ..... a delphi is $80 CDN when I can get jobber for around $20

Since I was so into the project, I went ahead and purchased new bolts although they can be reused if you use the right threadlock. My manual lists the threadlock to use as GM 12345382. I also purchased a new in-lb 3/8" drive torque wrench to install the parts. I had been wanting an excuse to get one. :)

I really don't know about the pressure regulator or why it would be messed up. Perhaps the act of taking the Intake manifold apart messes with a part that would be pretty old and fragile by then.

For me, when I decided to do the LIM gaskets it was after I had decided that I wanted to invest in the truck and keep it for a while. As a consequence of that I decided to also upgrade the fuel injector spider to the MPI version from the SPI with the poppet valves. Also, it is a pretty big job to get everything out of the way to get to the LIM gaskets. As such I decided that I might as well replace anything that would require the same work to access. While I was at it, I also replaced the spark-plug wires, spark plugs, rotor and cap as the wires and plugs were easier to access with so much on top of the motor out of the way.

I am hoping there will be no reason to ever go into the top of the motor ever again. :)

P.S. I went with AC-Delco for the fuel injectors since, as I mentioned before, I did not want to ever have to do the job again.

How about also replacing the thermostat and the short 'by pass hose' that goes from the water pump to the intake manifold. My indie shop replaced those two items when they replaced the LIM gaskets.... with the upgraded Fel-Pro.

Oh yes, I did replace the thermostat and had replaced the bypass hose a few years ago when I replaced all my hoses.

Like when I replaced the timing belt on my '82 Prelude, I went ahead and replaced the water pump too.

good recommendation Jim, some items should just be done since we are there anyways.

Christine, in each gasket at either end is a smaller opening. See your second photo and you have the 'note paper' positioned in one. Your photo's no. 6 and 7 also show that 'bad gasket part'. What is that opening for? In your photo's, only one of the four openings is deteriorated. The other three are intact. All four of those openings in my old gaskets were gone--melted away! I figured that was the cause of the excessive coolant loss. Great photo's , by the way. My gaskets looked similar look similar in appearance and I think they may be the GM original gasket set. Thanks, Jim

Jim,

I should have noted that the one "broken" (right front) water passage seal frame was broken by me when I was removing the gaskets. I had no perceptible leaks before I removed these. So I suspect these are what gaskets look like on their way to failure.

I should have also added that there is a part number molded into the gasket carriers in the middle between the intake ports: 12451348 PA66. A quick internet search shows that the 8-digit number matches the GM part number for LIM gaskets. I also have no reason to think these are not the original ones.

You asked about what an opening was for? Are you referring to the one between the intake ports? I believe that is an artifact of the design of the carrier to keep it rigid.