Hi Bob , and gang , Lot of good info I think -and new to me , 60 years later . Will forward a set of pictures for later . First , on rotor hitting cap . I had new -and I believe correct - F cap , rock auto / standard motor part . (By the way in stock there , USA made ) ,— Looks to be same cap set up as all early hemi dual point . However my F came with no cap , had what turns out to be a taller rotor installed on it — associated ( known now) with tan ( later) cap . This rotor height change , I was not aware of . Very confusing — The height is not the collision issue however — !!! both caps are 1..5 “ deep to contact ( pix to show) . But they also made the length of brass spinner on new rotor about 1/8 longer . To accommodate that they machined back contacts in the tan cap to allow more swing room . So — why also taller then ? — EE reasons. The taller rotor seems to swing well inside the tan metal cap contact , while the older shorter rotor I think may be even or even slightly below the nice brass contact . At least with these parts I have . Original rotor is a lot shorter height . See dimensions . All this fits , can be crossed up several ways . Tall rotor , old cap wipes out distributor . New cap, old rotor =big gap for spark and very likely cross firing. Poor performance . That may happen a lot . I see tan caps on iron distributors. Tan cap fits but ... ? Inside gap all wrong ??? Or might be right, an upgrade , with its rotor . But then parts # wrong on car . I realize now that the rotor hit I first experienced on bench was a sideways hit on old cap due to long rotor brass... hitting sideways on the old cap ( brand new one) . Supposedly correct cap for F I had thought it was a vertical hit due to free play vertically in advance system as described earlier , and I made a copper washer under spring clip to cut that rise , but still hit . Led to all this . But much better more stable thing now imho. As EE I see “why “ on all this , -leakage or “ creep distance” on new rotor is much better , jump distance in cap contact less(?) , overall insulation probably good for 50% more volts . Less breakdown likely . May be associated with resistance radio wire debut too , would raise volts Inside cap . Or maybe they found it was cross firing or breaking down . Whatever . Pix later , on site ? On egg shaped hole , on vacuum advance arm, very carefully squeezed the egg back to round in loaded direction for now . Nice and tight . Play gone . On vacuum can got confused by H shaped hole in can where arm comes out . That is apparently there for factory assembly of can , but when on distributor center of the H is a stop limit for arm with no vacuum . Arm must end up in center of H on car. This arm had fallen into one leg of H (!) (? Messed with or bent?) so it was out too far at rest. Heads up .F can is stamped “N” no numbers . Interesting day here , like it . Small stuff, big impact — Hope this helps .. John PS Brain strain ? If hemi and B spin opposite , the whole advance setup must be a mirror image , as hemi advance direction is B retard with rpm .I think . Arrgh never thought about that .. re mixing parts. Sent from my iPhone not by choice ------------------------------------ Posted by: John Grady <jkg@xxxxxxxxxxxxxxxxx> ------------------------------------ To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or go to https://groups.yahoo.com/neo/groups/all/manage/edit For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang ------------------------------------ Yahoo Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: Chrysler300-digest@xxxxxxxxxxxxxxx Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo Groups is subject to: https://info.yahoo.com/legal/us/yahoo/utos/terms/