Originally Posted by huppfan
Has anyone used pipe thread compound on a small block Chevy to seal the head bolts that extend into the water jacket? If so how well did it hold up?
Paste type Teflon pipe joint compound works just fine. The stuff provides lubrication similar to the specs for oiled threads. By placing some into the bolt hole, a supply can be kept moving ahead of the bolt to insure that coolant doesn't get into the thread area causing corrosion in the lower interface.
Be careful when using any sealer to check that the hole isn't blind. Any sealing compound, oil, or other fluid that's pushed ahead of the bolt to the bottom of a blind hole will cause a hydraulic lock where forcing the bolt against the filling material risks cracking the casting.
Be sure the tapped holes and the bolts are clean and threads are undamaged. Having a thread restorer kit is priceless, these are not thread cutting tools but rather restoration. Thread cutting tools be they taps or dies may not produce the same quality standard as used on the engine. Running a class 3 tap on a class 1 thread will remove material you don't want removed. The restoring tools coax the threads back into position and cleans the gunk out without removing material from the thread itself. Check out this URL for an example kit http://www.sears.com/shc/s/p_10153_1...0070921x00003a
I've used Teflon paste for decades on many, many engines for street and competition without any issues what-so-ever. Unlike RTV or epoxy materials, the paste pushed into the cooling jackets doesn't harden and the action of the water pump breaks up anything circulating into colloidal particles so the stuff won't cause unwanted blockage of cooling passages.