So yesterday I also tested this but it didn’t help at all. I did also the test with breathers instead of the PCV system but with no difference.Īfter all the above tests, I finally found some discussions about Holleys running to rich at idle when using cams with big overlap and the suggestions was to restrict the fuel into the idle circuit by putting a thin wire into the idle feed restrictor. I use a PCV valve in the drivers side valve cover and the passenger side valve cover is connected to the air cleaner.I have done all tests with the brake booster disconnected and the vacuum port plugged (if it was a vacuum leak there).I have searched for vacuum leaks but not found any (I replaced all hoses and used carb cleaner spray around the intake).The transfer slot is not exposed to much on any of the throttle blades (I have checked by having the carb upside down).I have drilled the primary throttle blades.I have tried different power valves (6.5, 2.5 and 3.5).The vacuum advance is connected to the ported vacuum.I have tried to bump up the initial timing to 16° BTDC.Manifold vacuum when idling in drive is low and jumping up and down (around 5, I guess).Manifold vacuum when idling at 900 RPM in neutral is about 9 Hg.I have tried to set the idle mixture screws but they are not responding at all and it feels like it running too rich at idle which for me indicates that the main circuit is in use instead of the idle circuit. Finally the engine is equipped with a brand new Holley 750cfm vac carb (3310-SA) with manual choke. The engine also have a very aggressive camshaft (I don’t have any specs of it). My engine is a modified Chevy 350 with ported double hump heads, roller lifters and lots of more performance stuff. I have read almost every article and threads on the Internet about this problem, but haven’t found a working solution for my setup.

Yes, this is another thread about idle problems together with camshaft with big overlap.

Race idle cam 350