the viscosity of silicon is tooo thick to seal a thread, it will just roll off. Also, is a leak proof thread nesc on an air inlet? If you want to seal threads telfon tape / paste or leak loc is the best. If you are sealing nat gas or propane be sure to read the lable...and use a thread sealer applicable to the job, as silicon is more for a gasket surface. Log onto a permatex web page for proper application.
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