Holley tuning questions

[Dmichels]

The last few days I have been trying to dial in the carb. Engine 440 older type. MP 509 lift 292 duration cam. Holley 800 DP Engine has about 6 psi vacuum at idle Now I have read you base your power valve selection on the idle vacuum either half or 2 numbers lower depending on who you listen to. The reason stated for this is you do not want the PV opening at idle creating an over rich condition. Now my understanding of the way the carb works is that the main circuit only starts working when you open the throttle. The main jets are always "open" but do not contribute fuel at idle. The PV enriches the main jet circuit so I can not imagine a open power valve at idle. would cause an idle issue. The reason I state this is my vacuum goes UP when I open the throttle. I really REALLY need to get on it to get the reading lower then 6. I have a 3.5 PV in there right now and I feel I may have a medium to heavy acceleration lean out as I have monitored the vacuum gauge during theses conditions. Is my thinking right to put in a higher PV? FYI my lowest cruse reading is about 10  Thanks for your ideas.
Dave

[BSB67]

The PV enriches the main jet circuit so I can not imagine a open power valve at idle. would cause an idle issue.

Correct. That 1/2 the engine idle is BS.  It is at best, a starting point.  However, too high of a vacuum rating you could be too rich any time you are on the main if your PV is open too early.  Usually light throttle under load.

Is there something in particular that you are trying to do?  It seems like you are trying to fix something, but you don't say what.

I've personally never usd the 509 in a 440, but your idle vacuum seems too low.

[Dmichels]

My problem was lack of power I put a 8.5 PV in there today and I can't keep the wheels from spinning. I just wanted some back up opinions on my thoughts  I will keep at it
Thanks for your response
Dave

[1974dodgecharger]

I run a 383 with your 509 cam with 292 and my vacuum is lower than yours im lucky to get 7 at best, but I always say 6.5.  I picked a 4.5PV for my tastes that's just me because the cam is big for the street your gonna have to compromise what you want to do.

So your saying you spin the tires too much?  I don't see the problem?

you just don't want the PV to enrich the circuits near the idle or slightly tapping the gas you don't want it to richen it up. 

I don't think the vacuum should be going up under acceleration?  Shouldn't it go to zero or something like that?

[c00nhunterjoe]

My 383 with the 509 equivalant. Your vacuum is too low. Check timing and leaks.

[BSB67]

My problem was lack of power I put a 8.5 PV in there today and I can't keep the wheels from spinning. I just wanted some back up opinions on my thoughts  I will keep at it
Thanks for your response
Dave

If you did nothing but change the power valve rating and the car is making a bunch more power, you probably accidentally fixed somethng else.

[Dmichels]

Thanks for the input I will keep at it
I will check the timing to see that will get me any more vacuum I checked for leaks and did not find any
What do you mean by I accidently fixed something else? Was I too lean on the primaries?
As always thanks for all the help
Dave

[1974dodgecharger]

My 383 with the 509 equivalant. Your vacuum is too low. Check timing and leaks.

same gauge coonhunterjoe in fact my gauge was off when I first bought it it was reading beyond zero for me so I broke into it and said screw I will adjust it myself to near zero and that's what I did.  I personally don't go buy actual numbers on a vacuum gauge.  To me its arbitrary just get it high as you want to give one a idea of whats going on and personally for me I adjust half turn out more for the 4 corner idle so I can have a richer idel.  I tune get some help by the O2 gauage I idle at 13:1 my preference, but if I tune it by the gauge I get 14 to 14.5 to 1 idle.

[c00nhunterjoe]

My point was, 6 inches of vaccum with that cam in a 440 is too low. Something is wrong. Even a low compression 440 with a 509 should hold more then that.

[1974dodgecharger]

My point was, 6 inches of vaccum with that cam in a 440 is too low. Something is wrong. Even a low compression 440 with a 509 should hold more then that.

huh, its always been low for me yours looks like 9???  That's how Im reading it....I can get to 8 to 9 myself, but at idle of 1k, but when I want a 800idle its low like 6.5 or so.

so maybe his idle is too low??

[Dmichels]

my idle is about 900 I guess I need to play with this a little. I am running a duel plane manifold with a window milled in the divider. Engine is a relatively fresh rebuild with about 9.7 to 1 compression. Cam is advanced x degrees I need to look up the number. Runs good now but always looking for ideas
Thanks