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I've got the timing set to 10 deg BTC. The manual says 6 deg BTC, but the car stumbled alot.

Now the car seems to be fuel starved until I step on the gas hard, then it takes off. Can the vacuum advance (or lack thereof) cause overall timing to be more correct when I stomp on the throttle.

The distributor was re-curved in Aug 2000, and the carb (Edelbrock 1406) is new since Aug 2000. Got any ideas as to how to time this one. The engine is a 289 with 9.5:1 compression ratio, Edelbrock Performer top end and '70 351W heads.

Thanks,

Mike
'66 Springtime Yellow Coupe
289, slightly warmed over
driven daily
 

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From my reading, your post indicates one of 2 posibilities, accelerator pump or ignition timing. It is possible that your acccelerator pump is not putting out a big enough squirt at the right time when the throttle is first cracked open resulting in a stumble off the liine. Not having an Edelbrock carburator, I'll defer to someone else on this forum who might be able to talk you through the finer points of an Edelbrock accelerator pump. The other possibility is ignition timing that is still off. A number of posts in the old forum dealt with this issue. Check the search feature over there for all the details. Essentially, the harmonic balancer on these cars has a tendency to slip over time rendering the timing marks useless. The method espoused is the maximum vacuum approach then back off a bit to avoid ping. Hook up a vacuum guage to a vacuum port on your intake manifold and gradually advance the ignition timing until you get your maximum vacuum reading, then back it off slightly and go for a test drive where you can accelerate up a hill or some other situation where the engine is under load. If you detect pinging, back off the advance a little bit more and try again until the pingng stops. Once you've reached that point, your ignition timing should be optimum. If not, perhaps your vacuum advance is not working correctly. Again, I'll defer to someone else on the best way to diagnose and fix that problem. Good Luck

67 Vintage Burgandy 390GTA with most of the bells and whistles
 

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So you have a Performer cam or what? If your initial timing is too low it will stumble when you first take off. Other things will make it stumble too as has been mentioned.

I would go up to around 14 or 16 on the initial timing if its a performer cam and see how that does as long as it is making more power and not pinging. More initial timing will need to have the idle mixtures re-adjusted.





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