boatnut
04-08-2015, 12:09 PM
Actually this information is not exclusive to the H&M log manifolds that we are working with but could be appropriate for other situations also. We are working on our 1969 18 (which as you can gather from other threads now includes a tank change) with the goal of having it look like it did when it left the factory in 1969. So included in our work is going through the engine but with the goal of having it externally look like it did including all the H&M hardware, decals, etc. We are using the same engine as originally in the boat but internally we are making some changes to the 302 (hydraulic roller cam, stroke to 331, GT40 heads). However we want to keep the H&M exhaust manifolds. This is not about that decision, we know they are not the best manifolds, and that there is some loss of performance and risk by using them but they look so clean and are the essence of the H&M marined engine in our opinion. We have had some erosion of the aluminum in the manifolds going on where the exhaust flow/heat enters the ports of the manifold (for some reason it is more evident on the two rear cylinders of the engine). About 20 years ago I had someone build a little aluminum up on one of the ports to fill an eroded pit. This time we noticed the other manifold had a similar pit. When we checked with a couple of good aluminum heliarc guys, they did not want to fill the pit (maybe 1/8" deep or so) as they could not tell how much aluminum was left and they did not want to blow through to the water jacket. Our engine guy suggested checking on some of the places that do ceramic coating to possibly protect the aluminum from the exhaust heat. He said they are using more and more ceramic coatings on piston tops, combustion chambers, etc. as thermal barriers and to control (lower or increase) heat flow etc.
I then talked to several companies that did this type of coating. Most were involved with coatings for the aesthetics, such as external coatings on exhaust headers etc. But some were using the coatings for protection of parts like we were after. I ended up with Performance Coatings in Washington state and talked to Brad Gua (www.performancecoatings.com ). They have lots of experience with using these coatings for various reasons (primarily corrosion and thermal protection) on marine manifolds. When I described what was going on and sent some pictures to them, they said they were very confident they could stop the thermal erosion going on in our manifolds by coating the ports with a thermal barrier ceramic coating they use that is made by Techline Coatings. They said they could only clean and prep the aluminum a limited amount due to access but they were confident they could protect the area where we had the most erosion. We also had some pitting where the exhaust entered the two risers so the inside of the risers were coated also.
Attached are some pics that show the pitting on the manifolds and risers and some pics after the ceramic coating was applied. The cost to prep and coat all these ports was $200. The coating feels smooth and hard like glass.
819428194381946819488194981950
Our plan is to use these manifolds for a season or so and then remove one and try and determine if the ceramic coating is in fact doing its job of protecting the aluminum from the heat erosion. If it seems to be working we will stay with them. If the coating does not seem to be holding up we will consider changing over to a new set of aluminum or stainless manifolds (as you all know the choices for a small block Ford are limited). We do realize that blowing a hole between the exhaust passages and the water jackets could cause extensive engine damage.
Anyway, the purpose of this post is to share this "experiment" and provide some info in case there are others that are trying to save these manifolds. Ed
I then talked to several companies that did this type of coating. Most were involved with coatings for the aesthetics, such as external coatings on exhaust headers etc. But some were using the coatings for protection of parts like we were after. I ended up with Performance Coatings in Washington state and talked to Brad Gua (www.performancecoatings.com ). They have lots of experience with using these coatings for various reasons (primarily corrosion and thermal protection) on marine manifolds. When I described what was going on and sent some pictures to them, they said they were very confident they could stop the thermal erosion going on in our manifolds by coating the ports with a thermal barrier ceramic coating they use that is made by Techline Coatings. They said they could only clean and prep the aluminum a limited amount due to access but they were confident they could protect the area where we had the most erosion. We also had some pitting where the exhaust entered the two risers so the inside of the risers were coated also.
Attached are some pics that show the pitting on the manifolds and risers and some pics after the ceramic coating was applied. The cost to prep and coat all these ports was $200. The coating feels smooth and hard like glass.
819428194381946819488194981950
Our plan is to use these manifolds for a season or so and then remove one and try and determine if the ceramic coating is in fact doing its job of protecting the aluminum from the heat erosion. If it seems to be working we will stay with them. If the coating does not seem to be holding up we will consider changing over to a new set of aluminum or stainless manifolds (as you all know the choices for a small block Ford are limited). We do realize that blowing a hole between the exhaust passages and the water jackets could cause extensive engine damage.
Anyway, the purpose of this post is to share this "experiment" and provide some info in case there are others that are trying to save these manifolds. Ed