Mystery Tappet Guides

[wideglide38]

Morning All,
I have a set of cast iron pan tappet guides that appear similar to the early ‘48-’52 aluminum only guides (according to Bruce’s book) with no drill oil passages and unlike the ’53-’65 guides with drilled oil passages, cast iron and with casting #’s 18600-53 & 18610-053. My cast iron guides have similar but different casting #’s(?-481 and ?-48?) like the ’48-’52 guides with #9-483 & #9-482. I thought these guides were later cast iron guides with a production oversight (no drilled oil passage); but, the earl style casting #’s throws me.

Could these be aftermarket guides? Did the MoCo make a replacement '48-'52 cast iron guides after the start of the ’53 & later guides to address aluminum guide issues during the ’48-’52 year models?

Thanks, William

[Jerry Wieland]

You see these occasionally but I have never heard an answer that I was happy with. If I was a betting man they are either early production, late production or late replacements.

Jerry

[wideglide38]

Thanks Jerry! Where's a time machine when I need one??

William

[diesel55]

tappet guides

Hello ..My 48 EL that i am 2nd owner has these cast iron blocks. Have seen others.

[wideglide38]

My late 48 FL has aluminum blocks. I wondered if the MoCo started with cast iron when developing pan motor, then switched to aluminum as a cost savings. I've seen quite a few cracked aluminum blocks (along guide inside the gear case). I assume one reason they switched back to cast iron blocks in '53.