Just got a recoed 750DP Holley last week which replaced a 750VS Holley. However, it is running shite!! Any help with tuning would be appreciated.
Prior to installing I swapped the 3.5" power valve out of the VS into the DP. I didn't touch the jets (70's in the primaries of the VS and 75's in the DP). I can't get the idle down any lower than 1100rpm and even then it gets a stumble and stalls (with the VS it idled nicely at 850-900rpm). THe vacuum at idle (1100rpm) is 10inHg. The timing at idle(1100rpm) is 18 BTDC (I have bumped it up from 16 BTDC). Adjusting the idle mixture screws to maximise the vacuum and then repeating to lower the idle and it still won't play ball!!
When taking off it also has a massive bog from idle. It's lucky I have a manual and can slip the clutch somewhat. I moved the accelerator pump cam from the 1 position to 2 because the idle is so high ,but hasn't made much difference.
I think I have gone so far along I don't know what to do next?
Is it a vacuum leak? If so, how to find it?
Does the bigger primary jets (75 vs. 70) effect the idle ?(I don't think so)