I have a Universal M50 and replaced the exhaust
mainfold studs during its rebuild
Getting ready to test run it and filled engine
. Two days later (I let it sit to make sure nothing is wrong) I saw coolant
dripping from the exhaust
Turns out that the holes in the head
into which the studs screw are connected to the coolant passages.
The new studs are the correct thread type (M8 x 1.25), but the non threaded part has a slightly smaller OD than the OD of the threads.
The old studs have a non-threaded OD that is slightly larger than the OD of the threads. When the old studs go in, the larger OD forms a seal, preventing coolant from leaking.
Problem is that I cannot find studs that are the correct dia/thread pitch/length and also have a non-threaded OD that is slightly larger than the OD of the threads.
Does anyone know if there is a name for the type of stud that has a non-threaded OD larger than the OD of the threaded part?
Are studs just not made like that anymore (Engine was made in 1982).
If I can't find studs to fit, I'll have to use some kind of goop sealant
Does anyone have a recommendation of some kind of thread sealer that can withstand the temperatures of the engine head
near the exhaust ports