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#1
06-08-2011, 09:26 AM
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71 Grand Prix vacuum advance
Put my timing chain in the other day and disconnected and plugged the vacuum advance. Set it for 12 BTDC and checked total timing. Got 22 total. Question is the vacuum line from distributor goes to a 3 port electric over vacuum solenoid. Is this a decel valve. How do I check it for proper operation? Also I will pull the cap and rotor tonight and check the advance weights and springs. After all the engine was seized after not being started for 30 years. Any help would be great.
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#2
06-08-2011, 01:09 PM
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That is the TCS (transmission controlled spark) solenoid. The way it works is... it will allow vacuum advance only to operate in 3rd gear. It will also allow advance at certain engine temps as well... at start up when cold and also when very hot to help cool the engine down. If its all hooked up and working properly you will notice a slight drop in the fast idle during warm up when it reaches a certain temperature. The 3 prong temp switch in the front of the intake is part of the TCS system also.
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#3
06-08-2011, 01:59 PM
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Nice! So the temp switch will close at operating temp and will open when it runs hot! Great idea. That would explain why I had no advance when cold and running up the throttle. But it's also actuated in drive or is it 3rd gear? Mike
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#4
06-08-2011, 02:23 PM
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That's basically it... vacuum advance at dead cold (start up) or very hot, advance when it shifts into 3rd gear (drive). On 4-speed cars you get advance in 3rd & 4th gears. On my '70, the temp switch wasn't working properly and was allowing advance at all times. I installed an nos switch and it works perfectly now.
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#5
06-08-2011, 07:56 PM
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Very Very Intresting , i was wondering how that all worked.
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#6
06-08-2011, 09:20 PM
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Thank's for the help. Rebuilt the carb and put it on tonight. Runs better and secondarys go to open but it bogged and popped. Have to check the advance and check fuel delivery. Trying to get it ready for the POCI show in Merrimack N.H. Gonna register the old girl in the a.m. Mike
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