I just finished a project to clean up and refinish the exhaust manifolds on my 1995 Impala SS as part of a larger engine rebuild project. Here's what I started with:
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These are pretty typical for 25-year-old manifolds that have been on the car for 266,000 miles. There's rust on everything. The check valves are rusted to the pipes, 3 studs were rusted in place and had to be removed by a professional, and the only way to clean up the manifolds is to remove the shields. I was able to remove the air injection pipes from the manifolds without destroying them. The next step was to start removing rust. I did that by soaking the manifolds in a chelation solution (I used Rust 911) for 24 hours. Here's the result:
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Better, but there's still work to do. I had to remove the shields to remove all of the rust from the manifolds and to refinish the shields themselves. The shields are secured to the manifolds using part number 10229247 "engine air heat stove drive pins". My parts manual says that 8 are used for both manifolds, but the second design manifolds used on my car had 9. I was able to remove about half of them with a cold chisel (strike from the sides until you can create a gap) and a claw hammer. The heads broke off the others, which meant that the shafts needed to be drilled out using a 9/64" bit. Spot welds are used to join the shields in several places. I drilled out each of those with a 1/8" drill bit. After I separated the shields from the manifolds, I bead blasted the parts.
On to refinishing. Instead of ceramic coating or painting the manifolds, I wanted to try something that would all easy touch-ups. I've read about people having some success with dry graphite, so I decided to try that using Slip Plate Aerosol. The color came a little closer to raw cast iron than the other brands I tried. The shields were primed and painted using Rust-Oleum high heat primer and high heat flat aluminum spray paint. Here's the left side before reassembly:
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I used 1/8" aluminum pop rivets to join the shields where they had been spot welded. The drive pins were reinstalled using a ball peen hammer. I was able to save the left side air injection pipe, so it, too, was bead blasted and given a shot of high heat clear paint. I added a new 22048212 check valve, new 10220453 studs (installed with high heat anti-seize), new 11516072 nuts, and a new 10168551 gasket. Here's the finished left side:
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The process for the right side was the same. Here are the parts prior to reassembly:
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The threads on my right side air injection pipe got stripped when I removed the check valve. I managed to find a new 12552899 pipe to replace it. Here's everything put back together:
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Hopefully these will hold up for a few more years. I was lucky in that these original manifolds weren't cracked or damaged, even though the rearmost left side manifold bolt head had broken off at some point. Reproduction right side manifolds are available, but I prefer to restore my original parts when I can.
One last note: I was able to buy all of the GM parts I described here by part number by doing a lot of online searching, but they're getting harder to find since many have gone obsolete. I was able to find replacement drive pins (part number ENC-343, $1.95 each) from Muscle Car Central, but they're just a tad longer than the OEM 10229247 pins. They worked fine, but if you have to drill any pins out you have to make sure you remove all of the old pin so that the hole is deep enough to accept the new pin. I hope this helps!
These are pretty typical for 25-year-old manifolds that have been on the car for 266,000 miles. There's rust on everything. The check valves are rusted to the pipes, 3 studs were rusted in place and had to be removed by a professional, and the only way to clean up the manifolds is to remove the shields. I was able to remove the air injection pipes from the manifolds without destroying them. The next step was to start removing rust. I did that by soaking the manifolds in a chelation solution (I used Rust 911) for 24 hours. Here's the result:
Better, but there's still work to do. I had to remove the shields to remove all of the rust from the manifolds and to refinish the shields themselves. The shields are secured to the manifolds using part number 10229247 "engine air heat stove drive pins". My parts manual says that 8 are used for both manifolds, but the second design manifolds used on my car had 9. I was able to remove about half of them with a cold chisel (strike from the sides until you can create a gap) and a claw hammer. The heads broke off the others, which meant that the shafts needed to be drilled out using a 9/64" bit. Spot welds are used to join the shields in several places. I drilled out each of those with a 1/8" drill bit. After I separated the shields from the manifolds, I bead blasted the parts.
On to refinishing. Instead of ceramic coating or painting the manifolds, I wanted to try something that would all easy touch-ups. I've read about people having some success with dry graphite, so I decided to try that using Slip Plate Aerosol. The color came a little closer to raw cast iron than the other brands I tried. The shields were primed and painted using Rust-Oleum high heat primer and high heat flat aluminum spray paint. Here's the left side before reassembly:
I used 1/8" aluminum pop rivets to join the shields where they had been spot welded. The drive pins were reinstalled using a ball peen hammer. I was able to save the left side air injection pipe, so it, too, was bead blasted and given a shot of high heat clear paint. I added a new 22048212 check valve, new 10220453 studs (installed with high heat anti-seize), new 11516072 nuts, and a new 10168551 gasket. Here's the finished left side:
The process for the right side was the same. Here are the parts prior to reassembly:
The threads on my right side air injection pipe got stripped when I removed the check valve. I managed to find a new 12552899 pipe to replace it. Here's everything put back together:
Hopefully these will hold up for a few more years. I was lucky in that these original manifolds weren't cracked or damaged, even though the rearmost left side manifold bolt head had broken off at some point. Reproduction right side manifolds are available, but I prefer to restore my original parts when I can.
One last note: I was able to buy all of the GM parts I described here by part number by doing a lot of online searching, but they're getting harder to find since many have gone obsolete. I was able to find replacement drive pins (part number ENC-343, $1.95 each) from Muscle Car Central, but they're just a tad longer than the OEM 10229247 pins. They worked fine, but if you have to drill any pins out you have to make sure you remove all of the old pin so that the hole is deep enough to accept the new pin. I hope this helps!
