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It's important to remember that the vast majority of the time, we are obviously working with very old aged components. We may be trying to introduce a new component to and old component , like in this case, a new insert to a very old head casting.
For the reason mentioned above, We have to come up with feasible, affordable and proven solutions for this repair. We can not take an approach of this "brand new" part fits perfect with this "brand new" part. Lets be honest, that is unrealistic and an attempt to make it "brand new" is typically unaffordable for the majority of antique enthusiasts.
So lets get back to age parts fitment. The first thing that needs to be acknowledged is "Surface Asperities" (Roughness). Every machined part has asperities. The initial asperities change on a particular part over time for many, many reasons. Abuse, corrosion, bead blasting, an attempt to resurface, wrong tooling, lack of mechanical knowledge, etc... all have an affect over time.
On a intake manifold insert per this post, Your sealing is achieved on the flange surface of the insert to the head casting, not the threads. Why??? Lets take facts about threads. Threads have a Major and Minor Diameter. This is determined and achieved when machining the threads. So Harley Davidson's Major and Minor Diameter in the Cylinder head casting threads may be different than Colony's Major and Minor Diameter on the Insert. This same thing can occur on mismatched hardware...So there is "one" thing to note!
Second, remember we are talking Old Antique parts again, so years of Mechanical service, Dis-service and Restoration come into play. Years of possible corrosion, Sand blasting, Bead blasting, wire brushing, Cross threading, Galling, etc. all change the asperities, hence the contact area of the threads. NOTE: The majority of all new fastener system threads only contact 10-30% when torqued. This means there is an "Air Gap" in the threaded area of 70-90%! Elastic deformation spreads the load and creates this gaping. The first 2-3 threads carry the majority of the load distribution and it tapers off from there on the other threads.
So why use a proven sealer? When torqued to a value, the sealer takes up the void ( 70-90% air gap). Taking away the air gap with a proper sealer aids in torque retention and takes away the opportunity for air to wick around the threads and leak. The sealer chosen must resist chemicals seen in its environment of usage, resist temperatures seen in that particular environment and Cure properly. If this is all achieved, the flange surface that does the actual sealing but probably doesn't do its job very well anymore for reasons I've listed above, can be backed up by threads that are sealed on 100% of their area, torqued to a actual value and will not allow air to wick past and lean out our Air Fuel Ratio.
I hope this helps,
Duke Kleman
For the reason mentioned above, We have to come up with feasible, affordable and proven solutions for this repair. We can not take an approach of this "brand new" part fits perfect with this "brand new" part. Lets be honest, that is unrealistic and an attempt to make it "brand new" is typically unaffordable for the majority of antique enthusiasts.
So lets get back to age parts fitment. The first thing that needs to be acknowledged is "Surface Asperities" (Roughness). Every machined part has asperities. The initial asperities change on a particular part over time for many, many reasons. Abuse, corrosion, bead blasting, an attempt to resurface, wrong tooling, lack of mechanical knowledge, etc... all have an affect over time.
On a intake manifold insert per this post, Your sealing is achieved on the flange surface of the insert to the head casting, not the threads. Why??? Lets take facts about threads. Threads have a Major and Minor Diameter. This is determined and achieved when machining the threads. So Harley Davidson's Major and Minor Diameter in the Cylinder head casting threads may be different than Colony's Major and Minor Diameter on the Insert. This same thing can occur on mismatched hardware...So there is "one" thing to note!
Second, remember we are talking Old Antique parts again, so years of Mechanical service, Dis-service and Restoration come into play. Years of possible corrosion, Sand blasting, Bead blasting, wire brushing, Cross threading, Galling, etc. all change the asperities, hence the contact area of the threads. NOTE: The majority of all new fastener system threads only contact 10-30% when torqued. This means there is an "Air Gap" in the threaded area of 70-90%! Elastic deformation spreads the load and creates this gaping. The first 2-3 threads carry the majority of the load distribution and it tapers off from there on the other threads.
So why use a proven sealer? When torqued to a value, the sealer takes up the void ( 70-90% air gap). Taking away the air gap with a proper sealer aids in torque retention and takes away the opportunity for air to wick around the threads and leak. The sealer chosen must resist chemicals seen in its environment of usage, resist temperatures seen in that particular environment and Cure properly. If this is all achieved, the flange surface that does the actual sealing but probably doesn't do its job very well anymore for reasons I've listed above, can be backed up by threads that are sealed on 100% of their area, torqued to a actual value and will not allow air to wick past and lean out our Air Fuel Ratio.
I hope this helps,
Duke Kleman
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