terrycoxusa Posted November 7, 2007 Share Posted November 7, 2007 I finally got my exhaust hooked up, but I am not happy with the way the motor runs. If I leave the idle at about 800, the carburetor (new holley 390 on an arizona z car manifold will backfire about every 10 seconds) the manifold vacuum is about 17 inches at idle crane cam electronic distributor with 12-80 module timing set at 12 degrees btdc just rebuilt the engine, 2.8 flatop pistons any ideas? I'll recheck the valve clearances tomorrow I am getting 12 volts to the coil. Quote Link to comment Share on other sites More sharing options...
ZXR_KiD Posted November 7, 2007 Share Posted November 7, 2007 my only guess would be that your timing is off, or your exhaust is too restrictive..... just a guess Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted November 7, 2007 Administrators Share Posted November 7, 2007 Do you mean back fire up through the carb or out the exhaust? Quote Link to comment Share on other sites More sharing options...
terrycoxusa Posted November 7, 2007 Author Share Posted November 7, 2007 It backfires out through the carburetor. Quote Link to comment Share on other sites More sharing options...
Savage42 Posted November 7, 2007 Share Posted November 7, 2007 It's got a lean condition or it's a timing issue. Spray around with carb cleaner and check for vacuum leaks, check ignition & cam timing. Gotta be one of those things. How's float level & fuel pressure? Might be that, too. Quote Link to comment Share on other sites More sharing options...
terrycoxusa Posted November 7, 2007 Author Share Posted November 7, 2007 I checked the float level, the gas is right at the inspection hole. It has a brand new electric fuel pump, but I haven't checked the pressure at the carb. The timing is at 12 degrees, I had it at 10, no difference. The vacuum advance is working fine, rebuilt distributor. I have an ACCEL 12v. coil on it. Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 7, 2007 Share Posted November 7, 2007 It's lean if it's coming out the carb. If it's only at idle, I'm pretty sure Holleys have idle screws to adjust fuel on the idle circuit. Quote Link to comment Share on other sites More sharing options...
terrycoxusa Posted November 7, 2007 Author Share Posted November 7, 2007 I checked the cam clearances this AM, they were fine, noticed the 3 and 4 spark plugs were sooty and the others were a nice tan. I double checked the plug wire order, and sure enough, 3 and 4 were reversed. So I put it right and now it runs GREAT!!! Way better than my (tired) 280z with fuel injection. I can really feel that 4 barrel open up. Thanks all for your suggestions, check the simple stuff first. Quote Link to comment Share on other sites More sharing options...
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