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I just checked the vacuum on my new engine because it is running really rich at idle and was trying to figure out the cause. It is loading up and causing the plugs to soot up. The most vacuum I saw was about 15 with reving, but at idle it was fluttering between 2 and 3. Does this seem really low? What do you guys with monster cam get on your vacuum gauges? If I am only getting that little of vacuum them I would assume that the cause of my richness is that the power valve is opening. The smallest power valve is 2.5, would this actually work? or would is still open? I guess the first thing I need to figure out is if my vacuum reading is at all normal.
 

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try more timing--the demon acted the same way and there tech said to increase the timing to help vacuum to improvr idle signal
doctordesoto
 

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Thanks Doc, that seems to be what I am getting over on the Cleveland forum as well. I will try it once I get it back together, but if anyone else has any suggestions, please chime in, I am all ears.
 

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Yeah, a low idle vacuum can create puddling.

Try the timing and bump the idle to 1100 or so and see what happens. It's pretty common for an out of the box Holley to not be able to properly meter idle mixture at those low vacuum readings. Compensating with idle speed and timing are easy things to try first.
 

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Makes sense if that cam has steep ramps that you won't develop much vacuum - that still sounds kinda low. Double check for vac leaks - I think the propane tank with a hose on the end is faster/easier than carb spray personally. You may need a vac pump to keep it streetable, especially with P/B. Depends on what you plan to do. Advance it until it wants to die then back it off about 5 degrees. Probalby will not start the best there though, but it will likey run the best once you get the carb dialed into what the motor is calling for.....it's a slow process unless you have some data from the poor SOB who built it the same way you did and you can benefit from him. That's all a part of the fun though huh? ;>)
 

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Thanks Doc, that seems to be what I am getting over on the Cleveland forum as well. I will try it once I get it back together, but if anyone else has any suggestions, please chime in, I am all ears.
Mike,

Hello. Posidude's comment pertaining to timing adjustment with use of a vacuum gage on intake vacuum is right on. And, when using this method, you may also find that you will have to make subtle back and forth adjustments to the timing while dialing the carb in. Kind of the same process with the carb: adjusting needle screws to highest RPM at idle while timing is also yeilding the highest possible vacuum at idle. Does your cam grind offer idle range specs? If not, I would guess 1000 rpm to be a good starting point for tuning.

Also, The Ford D0ZF-9510-Z Holley 780 CFM carb for the Boss 302 had holes in the primary butterflies for aid in engine idle. Here's one of many links to info about the Boss 302 carb: http://www.mustangtek.com/4150/D0ZF-9510-Z.html

Happy Holidays !

Gary
 

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Discussion Starter #8
Thanks guys. Once I get the engine back in I will play with it. I don't think this cam is going to produce much vacuum though, it's rather large.
 
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