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msgdsrf · 09-14-2013, 10:22 AM

I'm thinking you shouldn't have vacuum at ported source in idle therefore you've opened your throttle plate too much to get the 135 idle and are on transfer circuit. This makes tuning hard. Your RPM drops are likely related to the drop in timing you found. Your mechanical advance is dropping 8 degrees which will give a big drop and I'm not sure about your vacuum advance because your wrote there is no change because there is no ported vacuum, then reported 6" ported vacuum...
I think you need to better stabilize the timing to reduce the in gear drop.
Also, 12" in gear seems a little low for a stock cam, so leak possible. Is your engine older? Possible valve train wear.

09-14-2013, 10:22 AM	#15
msgdsrf Registered User Join Date: Jul 2012 Location: White Salmon, WA Posts: 263	Re: Big RPM drop from park to drive??? I'm thinking you shouldn't have vacuum at ported source in idle therefore you've opened your throttle plate too much to get the 135 idle and are on transfer circuit. This makes tuning hard. Your RPM drops are likely related to the drop in timing you found. Your mechanical advance is dropping 8 degrees which will give a big drop and I'm not sure about your vacuum advance because your wrote there is no change because there is no ported vacuum, then reported 6" ported vacuum... I think you need to better stabilize the timing to reduce the in gear drop. Also, 12" in gear seems a little low for a stock cam, so leak possible. Is your engine older? Possible valve train wear.