Gen Posted March 17, 2012 Share Posted March 17, 2012 '78 280, runs ok for the condition its in. Noticed some interesting items under the hood. Would love some info. First, what looks to be my vacuum advance for my distributor is blocked off with silicone. Was this a performance mod? Second, I think this is my thermotime wire. Not sure and can't seem to pinpoint it in the factory service manual. Lastly, what the heck is this doing here, a diode? Any help would be great. Thanks, Gen Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted March 17, 2012 Share Posted March 17, 2012 In the third picture, that is a resistor. Don't know why someone would install it though. Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted March 17, 2012 Share Posted March 17, 2012 1. Blocking off the Vac Advance will make it "pop" under decel more. Not really a performance mod, but can sound cool with headers and a free flowing exhaust. It will also hurt economy under cruise conditions. 2. I'm pretty sure you are right about what the green wire connects to. Just look to see which one of the temp sensors doesn't have a connector attached to it, that if probably where that wire goes! 3. The only reason I can think of someone putting a resistor inline like that would be some kind of experimental way to enrich or lean the mixture. It looks like it might be in the wire that goes to the coolant temp sensor. Conclusion: Fix everything like that you find. None of that crap is buying you any extra power or fuel economy or driveability. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 17, 2012 Share Posted March 17, 2012 (edited) If you're talking about the blob or orangy colored stuff on the end of the can, that's just the factory seal of the adjustment hole. It's stock. The thermotime has two wires to a two wire EV1 plug, and looks jsut like the water temperature sensor plug. Don't get them mixed up. The temperature sensor for the gauge is one wire, maybe that's what you're looking at. Unplug it and see what the temperature gauges does. The resistor in line with the water temperature sensor circuit is a fairly common old time way to richen the mixture. It makes the engine temp look colder to the ECU, which then adds gas. It seems to pop up a lot on 78s for some reason. I have a 76, that seems to run on the rich side, but the ECU, AFM, block and head are all essentially identical to the 78, so the whole thing is kind of unclear to me. But several people have found them on their 78 cars. Maybe there was a rogue mechanic out there in the past, installing resistors on every Z he worked on. Edited March 17, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
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