[Dragncar]

Originally Posted by Sun Tuned

The bushings are exactly the same size od,id, and length.

The main reason they stay together better is the iron units at the bottom of the housing fully support and I mean fully surround the bottom bushing….tightly. This keeps any movement outside normal expansion rates to zero.
The fact that the iron housing was poured from the same exact iron formulation as the engine blocks, as they were poured in the same plant, keeps the expansion rates of both exactly the same rate.

The second and likely of equal importance here is the oiling for the iron distributors was much different than the later lighter aluminum units. As long as one used hood oil and changed it on a regular basis, you were pretty much gold.

Thanks for that. I have always wondered why they are so much tighter.
There is just something about pressing a bushing into cast iron.
What is you bottom gear clearance difference between iron and aluminum ?
Exactly what is 'hood oil " ?
I have not noticed and oil tubes with spring cups on my 2 Pontiac iron distributors that I have.
And can you trigger a MSD box with a HEI with the module unplugged ?
Exactly how does that work ?