Author Topic: Holley 750 dp, way rich at idle.  (Read 9475 times)

Offline Chryco Psycho

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Re: Holley 750 dp, way rich at idle.
« Reply #30 on: April 18, 2014 - 12:13:21 PM »
Powervalve will if it is not closed by the engine manifold vacuum

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Offline falkenracing

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Re: Holley 750 dp, way rich at idle.
« Reply #31 on: April 18, 2014 - 07:05:48 PM »
Thats one area that I have found many people to disagree, so I tested it myself, and it sure seems to work that way.
Can also tell that with the IFR restrictions (tiny wires) that i put in, in conjunction with the smaller jets, the car would'nt move and try to stall today when I was heading out to test drive it.
So tried removing the wires. AFR back to 12.6 (ish) and car worked well at low speeds, but leand out at about 2300rpm in third gear, so will be jeting up again and se how it changes things.

Offline Strawdawg

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Re: Holley 750 dp, way rich at idle.
« Reply #32 on: April 18, 2014 - 07:18:07 PM »
flow is a function of area..not diameter of the hole..dealing with very tiny diameters, a very small piece of wire can make a dramatic change in area...it can be like using a sledge hammer to drive tacks if one cannot find very small wire strands.

An incorrect power valve will allow fuel to flow thru the enrichment circuit at normal idle levels...no argument on that one :)  Need a power valve rated at a couple of inches lower than the vacuum in gear on an automatic or with the clutch in on a manual.

Tuning can be a very tedious business on  carbed cars. :)

Offline falkenracing

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Re: Holley 750 dp, way rich at idle.
« Reply #33 on: April 20, 2014 - 05:47:47 AM »
Well, have driven with the wirestrands in there for quite a while, the problem with it stalling out and excessiv leaning started when the jets were changed. And removing them solved the problem. Hence my thinking that Main jets could affect idle as well.

So, basicly, Idle and transition is a separate circuit wich feeds off of the IFR and IAB, nothing else(except mixture screws) will affect this, if carb's not messed up?

Power valve is functioning correctley.

Offline Strawdawg

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Re: Holley 750 dp, way rich at idle.
« Reply #34 on: April 20, 2014 - 09:15:07 AM »
Normally, it seems most suggest setting the throttleblades so that about 0.040" of the transition slots are exposed below the blades.  Is this in the ball park for your current set up?  this tends to eliminate the off throttle stumble/stall

Offline falkenracing

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Re: Holley 750 dp, way rich at idle.
« Reply #35 on: April 20, 2014 - 04:17:29 PM »
About 0.040 transition slot, give or take some, probably on the smaller side due to a nice ,low rpm, ideling camshaft.

Offline falkenracing

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Re: Holley 750 dp, way rich at idle.
« Reply #36 on: May 01, 2014 - 04:31:34 AM »
Now the carb is jetted 71 in primary and 78 in secondary, and as far as I can tell, the little engine liked the leaner condition it's now under. Low speed is at about 13.5-14:1 I would say (engine warmed up) and goes in to 15:1 at cruise to about 2300rpm, where it then drops to high 13:s.
Have thou, since the down jetting, got a little problem with the car stumbeling some on take off in low speed, wich was'nt there (or as evident) before. Tried changing pump cam on primary, wich made it better, but still there (went from pink to white, both in pos. 1, as this would give more initial lift from what I read).
Have a little concern that the quite big carb on this mild motor with lazy gearing gives me a harder time due to me cruising with the blades barley craked open, wich gives a very large amount of increase in airflow when i get in to the gaspedal. If i ease in to it, or cruise in first gear at lower speeds (even thou both second and third could easily pull at those speeds) the problem goes away, or eases of anyway.

Offline cudabob496

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Re: Holley 750 dp, way rich at idle.
« Reply #37 on: May 01, 2014 - 04:38:10 AM »
stumbling? change squirter size. Discussion starts about 1.00 minutes:


https://www.youtube.com/watch?v=tMKxD_OFuCA
« Last Edit: May 01, 2014 - 04:44:51 AM by cudabob496 »
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1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

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Offline falkenracing

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Re: Holley 750 dp, way rich at idle.
« Reply #38 on: May 01, 2014 - 04:56:38 PM »
Will be looking in to squirter size as well.