Valve wear with unleaded gas is more of a problem with high compression motors especially under hard use. The old low octane tractor gas that was around in the 60s didn't have much in the way of additives and still worked with low compression engines like the CMPs have. I've installed hardened seats in high performance 350 Chev engines to get around the problem but then had the seats come loose in the heads. It's sort of a no win situation. On the 350s I ended up going for heads with induction hardened seats and that worked.
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1940 Cab 11 C8 Wireless with 1A2 box & 11 set
1940 Cab 11 C8 cab and chassis
1940 Cab 11 C15 with 2A1 & Motley mount & Lewis gun
1940 Cab 11 F15A w/ Chev rear ends
1941 Cab 12 F15A
1942-44 Cab 13 F15A x 5
1942 cab 13 F15A with 2B1 box
1943 cab 13 F15A with 2H1 box
1943 Cab 13 C8A HUP
1944 Cab 13 C15A with 2C1 box
1943 Cletrac M2 High Speed Tractor
MkII Bren gun carrier chassis x 2
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