The carb on my Gran Sport was rebuilt by yours truly, who also forgot to check these 2 plugs during the rebuild. The car had no idle, but was responsive when throttle was cracked open. Carb was opened up and the plug was laying loose inside. Will JB Weld stick hold up to the gas or is something else better.
Gray Marine Tex is supposed to be good. I know Cliff Ruggles sells a kit for the plugs inclusing the epoxy.
The only effective method to seal up bottom plugs permanently is to remove them and install screw in plugs coated with Marine Tex. We pressure test every main casting that we build. Most of them have been previously "rebuilt" at some point, and JB Weld or other over the counter epoxy applied to/dabbed over the plugs. At least 9 out of 10 will fail a high pressure leak test. The expoxy will NOT stay attached to the material, and often "softens" in contact with fuel. In any case, if you want a permanent repair, pull the plugs, tap the castings, and install screw in plugs coated with fuel resistant epoxy......Cliff
Something to sonsider here guys, is why the screw in plugs are preferrable. It is not the epoxy that is attacked by the fuel, though it is sensitive to the chemicals, but the problem is the adhesive itself dries to a brittle compound, whic is sensitive to the heat cycling of the carb. These plugs are exposed to sub-freezing temps in the winter to temps exceeding 200 deg in the summer, more during a hot soak. The constant heat cycling causes the rapid, excessive expansion and contraction of the surfaces, which eventually causes the adhesive to let go. This progressive deterioration of the adhesive starts a slow leak, which increases as the adhesive deteriorates. Screw-in plugs eliminate this situation.
Exactly Ray. The heating/cooling cycles will cause whatever sort of glue/epoxy that you use to come loose from the base material. Some epoxies are NOT fuel resistant right to start with, even those that are will not stay attached, as we see every single day in the shop when we pressure test them.....Cliff
If i put the screw in plugs into the carb, is a sealer of some sort recommended? It sounds as if either method will work, but the screw ins may be better in the long run.
Yesterday we installed screw in plugs into 8 castings out of 10 that we pressure tested. All 8 that showed leakage had JB Weld or some other type of epoxy "dabbed" over the plugs at some point, and a high pressure test showed they were leaking. The only two that didn't show any leakage were from the 1980's, when they did a much better job of sealing them up. We tap the castings with a starting tap, and install screw in plugs coated with Marine Tex. The plugs seal on the tapered cut threads, backed up by the Marine Tex on the threads. We gently heat the castings to completely cure the Marine Tex before any fuel in put in the carburetor. To date, never had a single plug leak repaired in this manner. As mentioned in my book, "dabbing" epoxy over leaking plugs is about as effective as cutting your arm off and putting a bandaide on it!......Cliff
Here's my vote for Thumbs Down to JB Weld, even on the threads of custom made plugs... :rant: This is what I get for not checking V8Buickl.com before I work on the car! I hope that I can scrape the junk off and find some fuel resistant stuff...
