Timing issue |
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StarskyHutch75
New Member Joined: 01-March-2019 Location: Manassas VA Status: Offline Points: 11 |
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Posted: 19-June-2022 at 4:11PM |
I have a 408w in my 75 and I just installed a ready to run msd distributor. The engine builder said timing should be set at 12° at 1000rpm and full advance should be 36° at 3000rpm. I changed the springs and bushing out using the msd instructions and charts. My bushing and springs would give me 35° at 3000rpm when set at 12° at 1k. Is the 1000rpm what my curb idle should be set at? It seems kinda high to me. I installed the msd to replace a junky amazon hei distributor but the car ran fine before msd install. Now it runs rough and isn't drivable in its current state. Should I just replace the msd back to the way it came out of the box? I forgot to mention I'm running vacuum advance but I've made sure to cap it off when setting timing. Any help is greatly appreciated as I miss driving my car
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72 RS 351
Senior Member Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 2767 |
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The initial timing you can play with and vary to see how it helps the running, at idle and transition etc. It's good to have a baseline recommendation from the engine builder. I'm not going to criticize him at all for that. He may have built other engines like yours that he learned run very well at the 36* total, etc. But he may also be off some if he hasn't built one just like yours, and is guessing based on other engine builds. So it hopefully it's just some adjustment you need to do with the timing, or the fuel. What carb do you have on it, and is it made or set up for that 408 combination?
Edited by 72 RS 351 - 20-June-2022 at 7:02AM |
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Don
73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000+ rpm 351-4V &4R70W 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W |
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Big Bird
Senior Member Joined: 25-August-2013 Location: New York Status: Offline Points: 4194 |
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At 1000 RPM, the distributor will be getting some advance from the vacuum, and likely the mechanical advance as well. The builder is giving you good "initial recommendations" but the "best results" final numbers will depend on your distributor, idle, carb, intake, etc.
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"What we do in full frontal view, is more honest than your cleaned-up mind."
Randy 1979 T-Bird 2005 F-150 STX RCSB 4.6, 3.55 LSD How the Heck does a REGULAR CAB SHORTBED weigh over 5200 pounds? |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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the rest of the world sets base timing at normal idle in park with the vacuum disconnected and plugged. 12* is a good starting point but you might find that any combination of bushings and springs might need a slight tweak to achieve a base timing that gives your desired 'total timing. total timing does not include any vacuum advance, just what the base setting and what the internal mechanical advance mechanism provides at 'X' rpm. so you might find 13* base and your bushing gives 36* total for example. the question is "why the heck does it not run well with the MSD distributor? back to basics, vacuum leak? have you done anything with or changed the carb? hopefully your cam & lifters are not failed
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72 GT Ute
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