problem tuning carb

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prodart340

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catsncudas and I have been trying to get the "new" motor tuned in and the carb is acting funky so I thought I'd ask for some insight. The motor at idle is pulling between 5-6 pounds of vacuum and it has a 2.5 power valve installed. Ocassionally for no apparent reason the idle will increase by as much as 400 rpm. We checked for vacuum leaks, but found none.We're leaning towards a bad power valve and tomorrow I'll pull the carb and check it but I was wondering if there is anything else I should be looking for? thanks in advance for any tips,,,,,,Mike
 
5" of vacuum is low and the cam must be pretty big. What size engine and cam?

What is initial timing or is it locked out?

If it's not locked out it could be bleeding mechanical advance in depending on engine RPM.
 
416" with 600'ish lift solid roller,actually604/603 lift,,,291/303 advertised duration,258/270 @.050
 
Add about 8-10* to the initial and see how it idles, 20-23 range. 12.5 isn't near enough, IMO.
 
I agree the bigger the cam the more initial timing need. Step number one in tuning an engine is to get the timing right.
 
Sorry, just have to ask, is this a Vacuum advance distributor? And which one is it?
Cam is degreed in?
 
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