Aluminum alloy Tappet blocks

[dukekleman]

Can anyone say for certain why Harley Davidson stopped making their tappet block out of aluminum alloy and switched to cast iron based tappet blocks?
We know they ran cast iron tappets from then up into the early Evolution series engine and then switch back to aluminum alloy again...
I'm asking because my 1950 FL has the original aluminum alloy tappets. The have been tried and proven on this bike, my issue with them is that back in the 70's, they got chrome plated by the owner as well as the gear cover. I'm considering having the chrome stripped. Problem being then they be a polished smooth finish. Not sure what to do?
Use cast iron tappets and a different gear cover? Leaves it alone? Strip it anyway?
Thanks for any input in advance.
Duke

[T. Cotten]

After the chrome is stripped, Duke,

The aluminum can be re-textured with steel shot.

Cheap plating sometimes comes off with the shot alone.

.....Cotten
PS: For production dates, I would refer you to Bruce Palmer III's "How to Restore Your Harley-Davidson".

[dukekleman]

Thank you. I appreciate it.

[T. Cotten]

As to 'why', Duke,..

You might notice when you disassemble that the steel tappets are more worn than the block bores.

It seems that abrasive particles embed in the soft aluminum, to then cut away at the tappets. 'Why' they returned to aluminum in modern times was pure bean-counting, I'm sure.

Aluminum blocks can be "blue-printed" to accept oversized tappets with a Sunnen keyway mandrel.

....Cotten

[dukekleman]

Yes, I've Sunnen horizontal honed oversize many cast iron tappet blocks, Aluminum evolution and even the right case half tappet area on Twin cams. However, I have no real experience with these early aluminum alloy tappet blocks.
Cotton, are there any negatives to them a person should know about?
Thanks

[T. Cotten]

Yes, I've Sunnen horizontal honed oversize many cast iron tappet blocks, Aluminum evolution and even the right case half tappet area on Twin cams. However, I have no real experience with these early aluminum alloy tappet blocks.
Cotton, are there any negatives to them a person should know about?
Thanks

Evos and Twinkies might as well be flying saucers to me, Duke.

(Its hard to imagine the MOCO would go back to brooching tappet bores, or however they did the oil drain. But then they leapt backwards in plenty of other ways!)

And the negative, as I posted, is that they often wore out the tappets.

....Cotten
PS: So you have a keyway mandrel?

[otis71]

I have a set of oem cast iron pre 53 blocks that don’t have the oil holes for the hydraulic tappets. Can anyone identify them? I was once told late 52 running change by someone probably just guessing.

[MMasa]

Didn’t very early 1948 Pans run cast iron tappet blocks?
Mark