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Old 09-20-2005, 04:48 PM
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it goes pop!

my 70 nova ss, 350, just wont co-operate w/ me. i'm not sure what the timing is at but it starts n runs great. it idles at 1100 rpm has HEI dist. W/bosch 60,000 coil. a 750 dbbl pump. {the choke is not on} the engine is fresh w/ maybe 2k on it, but ever since i got it back from the shop, it goes pop. in the exhaust, not the carb. the carb is new and not the one that was on it. the old one was/is a holly 600/650 single pump, vac sec. "top loader" meaning the fuel bowls are attached to the main body permanently. the pop is faint n a small hesitation/power loss is noticeable. this happens at cruise, and accel. ask me/tell me anything pls Also, the block is .030 over, decked .010, heads are 336X with 2.02 in and 1.60 out, angle plug 70cc chambers (I think) 1 and 5/8 headers and 2 and 1/2 inch exhaust. ah yes, the number on the carb is 4777-7 which makes me wonder if it's really a 650 and not a 750......anyone? should i try larger jetting in the primaries?

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Last edited by Nova Boy; 09-21-2005 at 04:09 PM.
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Old 09-20-2005, 05:22 PM
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First thing is to verify what your timing is at both idle and full advance. Secondly make sure all your wires, your cap, rotor, plugs, etc all look good. You should read your plugs and find out if your running a bit lean (which might cause a poping) or what exactly is going on in the cylinder.
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Old 09-20-2005, 05:36 PM
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Spark plugs, spark plug wires, dist. cap, rotor, and coil are all brand new. Secondly checking the plugs after the car has been ideling will only tell me if it's rich or lean at idle. (the idle circuit does not effect anything but how the car idles)
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Old 09-20-2005, 06:28 PM
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What cam are you running? You may not have enough cam for that 750 cfm carb.
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Old 09-20-2005, 08:18 PM
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In regards to the cam...

Comp Cams part number 122422 gross valve lift .470 intake/.480 exhaust duration is 268 in 280 out, duration at .050 is 224 in 230 out, lobe seperation 110 degrees and I'm running comp cams pro magnum roller rockers with 1.52 ratio.
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Old 09-20-2005, 08:27 PM
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It sounds like a lean missfire to me, does it
surge at a constant load??
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Old 09-21-2005, 04:06 PM
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not really a "surge". just, pop mmmmmm pop popmmmmmmm pop...ect. but not like a back fire...
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