Not to highjack the thread.... but
a couple of years ago a dozen or so guys ( split between pilots / car guys ) toured one of the Roush shops in Livonia,
the front half of the building is Roush Aviation that rebuilds Merlin / Allison V12's for Spitfire / P51; 1650 CID, 1650 HP, 1650 Torque I believe they said
when they run one in on the test stand, everything on the shelves of the adjacent building's owners office fall off, they were looking for a new dyno location!
anyway I diverge, when they rebuild the heads some of the valve guides are not usable and they are dropped into a 5 gal bucket.
I asked what did they do with them? Oh we turn them down to be used in our distributor rebuild cell,
Later when we toured the back half of the building, the custom engine shop had many customer engines being rebuilt, including;
west coast vintage race cobra 260 engine, 427 SOHC, B302, B429, Chrysler vintage hemi, some bowtie pieces
off on the side was a small room with a Sun distributor machine with a couple of quart jars full of various weight springs, 100's of them
the tech said "oh yah we can rebuild your HiPo distributor, we use the valve guide bushings to replace worn distributor shaft bushings.
I didn't ask what the material was but they looked like bronze or sintered material tubes
there were also some prototype GT500 engines being built for Ford as well as some Chrysler V6 development engines being built.
regards,
jim p