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Discussion Starter #1
Well I have a holley 670 street avenger on my 347 and I havent done any adjustments to it yet. I already read that I screwed up by running the electric choke to the hot side of the coil and now need to find another 12 volt source thats dead with the key off.

The car just isnt running right. When I shift gears at higher RPMs the car wants to backfire. I think this is a timing issue since I just had to replace a defective Mallory distributor. Does this mean its too far advance or retarded? I was told to start around 32* advance at 4000RPM.
Is this approximately where you guys start?

Also while reading up in the Holley manual I was reading about adjusting the idle mixture screws. Says to hook up a vacuum gauge to the manifold vacuum port on the throttle body and adjust the screws equally untill the highest vacuum is met without adjusting the curb idle. It also says if you dont have a vacuum gauge (my case) use a tach to aquire the highest rpm.

SOOOO do I do this to aquire the highest RPM then adjust it down with the curb idle....down to around 900RPM or so at idle?

If you can chime in on these issues itd be much appreciated!
 

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Discussion Starter #2
also the jets are 65's on the primaries and 68's on the secondaries. Have you guys played with swapping these out? It stated about using lower jets 1 digit lower for every 2000ft in altitude since these are jetted at sea level.....???
 

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Start with timing about 8* at curb idle. Adjust idle screws to give maximum idle rpm, and adjust curb idle speed down to about 800 rpm or so. This gets you in the ballpark. As for timing, 36* or so at 3500 or so rpm is usually recommended for SBF, but that requires you to know how much mechanical advance your distributer provides and at what rpm. If you can't do that, adjust timing up and take it for a drive. Going uphill and goosing the accelerator to determine if you ping or not is a reasonable shade-tree mechanic technique. Once you find your initial idle is giving you pinging or detonation under load, back off timing 2 degrees at a time until you don't have detonation anymore.
 

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If you use vacuum advance, which vacuum source do you use ported or full vacuum?
 

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Discussion Starter #5
mechanical advance
 

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You might try pulling a plug after you have shut it down under full throttle and see what they look like....sounds to me like you are small for a 347 on your jet sizes. You may be getting a lean backfire. Also you need to find out how many degrees advance your distributor provides. You can get a rough idea by setting initial at 10 and then running the rpm's up to 3500 or so on a timing light and see what amount of advance your distributor provides. My thought is all the advance should be in by 2800 rpm. Good luck. :track:
 
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