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Discussion Starter #1
Not sure if this is normal or not:
After tuning my 69 302/4v I'm getting a slight throaty kind of noise upon deceleration in the rear of the muffler. It's not really a backfire and only happens when dropping from about 2500rpm-650rpm usully during a gear change. Any advice would be appreciated, cheers, Rob
 

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Discussion Starter #4
New plugs, points, condenser. Checked gap, dwell, timing set at 6 degrees BDC, idle at 650rpm. Idles fines, maybe I should check:
¥ for vacuum leak at carb /advance?
¥ leak in exhaust headers (er, how do I do this?)
¥ for too lean an A/F mixture in secondaries, the adjustable screw nearest the choke, yeah? (Edelbrock 650 Performer 4v)

Any other ideas?
 

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Just for the heck of it, raise the idle speed up a little and richen the idle mixture just a tad...see if that helps..

When you romp on it, any pinging? If not, try advancing the timing, a little at a time, until it pings, then back it off slightly. Re-check for the noise...

My instinct is that one or both of these areas will contain the answer to your query...
 

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Discussion Starter #6
thanks, I'll try raising the idle speed up a little. and adjust for a slightly richer mixture. No pinging when running 91 octane watered down CA gas /forums/images/icons/wink.gif I'll advance the timing if the carb fiddling doesn't work.
 
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