Series 80 Head Studs Coolant Outlet

[Author nameAuthor names are only available to PAS members.]

Hi, I am replacing my Car’s coolant outlet with a reproduction of the original, and I found my existing studs are too short to get a full nut engaged. Looks like a stud length of 4 1/2 inches will work but I am not finding any. Suggestions?

[Author nameAuthor names are only available to PAS members.]

Getting two made at a local shop: problem solved!

[Author nameAuthor names are only available to PAS members.]

Thanks, Peter; I was trying to avoid use of threaded rod in favor of finding a double-end stud of the appropriate length, but these seem to be harder to find than I expected. I was surprised McMaster do not seem to offer any double-end studs.

[Author nameAuthor names are only available to PAS members.]

Dornan makes all kinds of fasteners. They make a nice standard length stud for the S.80/81 engine. I have not looked to see if they have the longer studs needed for the water neck.

Randy, you are correct to NOT use threaded rod, the threads not only reduce the effective diameter of the 7/16″ stud to less than 3/8″, but each thread has a sharp edge to the bottom of the thread groove, and this is a stress-riser, allowing the stud to break or stretch much easier,

I have not done a torque-to-failure test on threaded rod, or ‘all-thread’, but I’m sure it will fail and breaks at half the stress that a 7/16″ stud will.

Greg

[Author nameAuthor names are only available to PAS members.]

The thread root is always the weak point; avoid the hardware store all-thread rod and buy B-7 which will be strong material with rolled threads (increased fatigue resistance) so it should be good but I still can’t believe a double-end, equal-length stud is so impossible to find.

[Author nameAuthor names are only available to PAS members.]

Randy,

Apropos of stud thread strength, etc., I believe that the torque on a Series 80 cylinder head stud should be no more than 50#.

The integrity of the material to endure repeated heat cycles is likely more important than stud / thread strength, per se.

Peter

[Author nameAuthor names are only available to PAS members.]

The Dynamics of a head stud or bolt:

Initial torque is the least tension a head bolt or stud will endure.

As the engine warms up, the head expands, increasing the tension on the stud or bolt. The bolt also grows

longer, which relieves some of the additional tension, but not all. This is one reason that when we re-torque

the cylinder head fasteners after replacing a head gasket, the re-torque is to be done with a cool or cold engine.

Each firing of the cylinder exerts a stretching force on the fasteners, trying to lift the head off the cylinder

block, and trying to spit out the head gasket.

An older tired engine will have weaker combustion pressures, a fresh engine with very little leakage past rings and valves will have higher combustion pressures.

An example of the above phenomenon in Diesel engines: When a Diesel engine is ‘hot-rodded’ the turbo boost and combustion pressures increase drastically, often resulting in blown head gaskets. The proper and safe procedure is to purchase special high-tensile strength head bolts to withstand the additional ‘head-lifting’ forces.

Greg Long

[Author nameAuthor names are only available to PAS members.]

Randy: I have made a head stud by using a good high-grade steel bolt, with the correct thread on the one end, and cutting the bolt to length for the stud, then threading it. Our cut threads are not a nice as a good rolled thread, but if a grade 8 bolt is used, the danger of a stretched or broken threaded portion of the stud is minimal.

Greg Long

[Author]

Posts