305 H.O. Timing Mark... '84 MCSS

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Tynan918

Royal Smart Person
Aug 2, 2021
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I'm seeing a lot of different answers about where the harmonic balancer groove is supposed to sit on the timing mark tab...

My emissions decal says "6° BTDC @500 RPM"... I live in Tulsa, OK, elavation here is 722', low altitude
Screenshot_20210811-003123_Chrome.jpg


Currently, I'm set at 8° BTDC...
20210727_214121.jpg


I can't even get the engine to idle @600 RPM without it idling rough and stalling.

Reading around online, I see mixed answers saying 8-10° BTDC, and 12° gives the most power. I just want a good 'ol gas friendly 305 lol... I would like it powerful, but I ultimately want it to save gas.

6° ?
8° ?
10° ?
12° ?

Which one is the right setting for a 305 H.O. ?
 

Tynan918

Royal Smart Person
Aug 2, 2021
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Here is a video I recorded using a timing light... The groove is nowhere near TDC when the light flashes...

 

79 USA 1

Royal Smart Person
Sep 2, 2011
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Cheektowaga, New York
If you are still running the computer control system,before checking the timing you must disconnect the 4 pin conection for the distributor. The ECM is advancing the in timing much the same way a vacuum advance would on a non CCC system. I have the 305H.O. in my 88 SS set at 8 degrees.
 
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Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
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Galaxy far far away
You need to disable the computer advance to be able to check the base timing. 6 degrees is stock but 8 or more improves idle quality. Rough idle is generally caused by vacuum leaks. Try manually choking thd engine with youf hand, if it smooths out you ard running lean.
 

ELCAM

Royal Smart Person
Jun 19, 2021
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I wouldn't expect to get factory timing settings unless everything was new. New timing set, new distributor and all new vacuum hoses, rebuilt carb with new throttle shaft bushings and all that can leak vacuum perhaps even gaskets.
 

bracketchev1221

Royal Smart Person
Jan 18, 2018
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Is that the factory pointer? I don’t know about 84 but I know in 86 the pointer was at 12:00 instead of the older design 2:00 position.
 
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