So, working on my sons old (1942) flat head Harley. The intake manifolds are a threaded nipple that is then held in place by rivets that are put in holes that are radial to the bore. The rivets are installed from the inside and then peened over from the outside. These need to be air tight after peeing or you have a vacuum leak. I have tried twice now, but always end up with a small leak when we pressurize it and test it. So, what would be the best sealant to use on the rivet? The river and the nipple are steel. Heat, gasoline and pressure are present. Thanks in advance.
I would use sealant like Dirko sealant. We use it on regular basis when we are putting Stihl two stroke crank cases together, they don't use gaskets. As you know for those little engines to operate properly they need to be air tight and Dirko delivered that to us so far at same time being exposed to high temperature, gas, oil...