manifold gasket replacement

The engine on the TR6 was unusually noisy, especially on acceleration, with sort of a slapping popping noise in time with the speed. I eventually figured out it was a bad exhaust manifold gasket, and now i can pick out that sound from a mile away - it seems to be especially common on Ford trucks and SUVs.

I've done a fair amount of other cleaning work around the engine, but had never really dismantled the top end past the carbs, when we rebuilt them. Everything was pretty crusty under there.

With the inline 6 engine, there exhaust manifold shares a gasket with the intake manifold, so all of those parts had to come off.

manifolds coming off
rusty manifold

Once everything was apart, i did a thorough cleaning on both intake and exhaust manifolds and surrounding parts. The '69 intake has a coolant tube through the center of the casting to help moderate the intake temperatures. That tube was predictably filled with scale and crud, but eventually cleaned out with lots of scrubbing and flushing. Happily, nothing was corroded enough to cause leaks once it was clean.

I didn't want to paint either of the manifolds, so i looked for more durable finishes that would hold up there. I brought the aluminum intake to HydraMoto Vapor Blasting in Forest Lake, MN. He mostly does motorcycle parts, but did a great job on this.

Vapor blasted manifold

It has a really nice satin finish that looks great and should be more durable than the original aluminum since it gets slightly peened in the process. It looks freshly painted, but is just bare aluminum.

Exhaust manifolds are most often wrapped or coated with a ceramic or high-temperature paint. Wrapping isn't great for the part, i don't like the cost of ceramic coating, and after reading the paint instructions, that seemed like a huge hassle to end up with a fairly dull finish.

After some more research i ended up using Slip Plate on it, which is actually a graphite lubricant spray that does a decent job on cast iron parts like this. After a derusting bath and wire brush, it turned out looking like a new casting.

cleaned up manifolds

Because it's graphite coating it's not as durable as paint, and will rub off on your fingers. On the other hand, it buffs to a nice gray satin and can be touched up with more any time. I've only had it on there for a few months, so it'll be interesting to see how it lasts over time.

While reassembling, i replaced the coolant return tube that lives behind the exhaust manifold to fix a small but persistent coolant leak, and put all new studs and nuts all around. It sounds a whole lot better and makes the engine compartment a little cleaner at the same time.

tr6 engine bay