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holley rich idle help

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fisher2

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Discussion starter · #1 ·
I did a few searches and found a bunch of info, but I just would like some advise because I've done some of the things and they just aren't doing the trick. Here's what I'm working with: 350ci motor, holley 750 hp with vac sec, voodoo cam #60104 @ .050 233/241 dur and .504/.525 lift, flame thrower hei, 2800 stall converter all in my 70 velle. I just recammed it and put this carb on over the winter.
My problem is a burn your eyes idle. I just had to put new plugs in it to start it so I could try to fix it. What I have done so far is bump my timing up to 18* which allowed my to close down my primary butterfly to the .020 gap that someone recomended in another post. I turned my air/idle screws all the way in then out 1 1/2 as a starting point. Then I hooked my vacume gage up and found the max vacume. The rear screws were pretty close at 1 1/2 turns but I had to turn the front ones all the way in for the most vacume. I don't think this right. Also i check for vacume leaks and everything checks out.
What is my next step adjust my secondary butterfly?
 
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#2 ·
Have you checked your power valve? I have been having the same problem, and reading a lot of posts, Here are a couple things, drill small holes the the primary blades,start real small, drill out idle bleeds, you could try opening up the secondaries, Make sure you do your own research, i dont want you to screw up your carb.
 
#3 ·
I drill a hole of about .100 in each of the primary throttle plates, just one hole each and in the side when the carb is hand held and upside down so that you have to hold the throttle closed for drilling.
I also like a .015 wire in each of the idle passages. You bend a little L shape in a 3/4 inch long piece of copper wire about .015 in diameter, insert it in the idle passage in the metering block and put a gasket over it to hold it in place.
This leans out the idle and is a recommended modification from Holley.
 
#4 ·
turn the rear idle screws in to stop, then out about 1/8 turn. turn the front in to stop, then out about 1.5 turns. start it up, let it warm up good, adjust the fronts to lean best (highest vacuum) plus 1/8 turn out, you should be real close.

The horrible truth is that for a street car the four corner idle setup is best described as a "marketing innovation". Similar to milled off choke horns, pretty anodized red/blue/black/chrome/whatever main bodies, etc.

Thiss is not new info, I'm surprised you didn't find it in your search.
 
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Discussion starter · #5 ·
Hey guys thanks. I did find this info in my search. I was just wanting to know what to try next from what I already tried. I wanted to drill a hole at a last resort. So should I try adjusting my secondary butterflies or just go straight to the drilling? I'll try the mentioned air/idle screw reversal too.
 
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#6 ·
Tom Mobley said:
The horrible truth is that for a street car the four corner idle setup is best described as a "marketing innovation". Similar to milled off choke horns, pretty anodized red/blue/black/chrome/whatever main bodies, etc.
Click to expand...
Tom

So has it not been determined a choke tower less Holley main body will flow better than one with a choke tower?
 
#7 ·
I usually find, using a wideband meter, that the idle screws are out about 1/2 turn. Your results may vary. Also, with that cam, you're probably pumping some raw fuel through at idle. I get the same results.
 
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#8 ·
Go for the secondary butterfly adjustment first. At least you can set it back if you don't like it. The wire method works also in leaning the idle fuel circuit.

I am using both on my tunnel ram and don't have any rich idle problems.
 
#9 ·
Thanks guys. I'm fighting this myself. Not quite to his extreme, but I idle too rich. Once it gets warmer out I'll be trying some of this stuff.
 
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#10 ·
Dawg,

milling off the choke horn won't increase the flow of any Holley carb. Here's why: the amount of flow depends on the area of the hole or orifice. IIRC, (I calc'd this out several years ago but don't remember the exact number) the area of the choke horn is over 4 times greater than the area of the venturiis. This is not counting the fact that the venturi area is substantially reduced by the presence of the booster venturiis.

Milling off the choke horn is a marketing innovation, a sales feature. Most guys never understood this because most guys don't have a flow bench. People who do own benches, well, what would be the motivation to go through the work involved to verify that? Most of the claims of higher flow are phony or there are other changes at the same time like cleaning up the casting lips in the venturiis, changing the boosters, slabbing the throttle shafts, using thin butterflies, using a lager baseplate, etc. Also, a carb that flows 750 at 28" pressure drop will flow more if you turn up the pressure drop to 32" or something. Some of the shops were doing that without mentioning it, claiming that the 32" number better represented actual conditions. That might well be true in itself, but the comparison is totally invalid if the two carbs are tested at different pressure drops.

The guys who are claiming to magically convert a 750 to a 950 or 1000CFM carb know their customers don't have flow benches to test the claims and if somebody does they can fall back on claims the flow bench setup wasn't the same as theirs or some other environmental condition affected the tests. Or, the traditional approach, just blow it off. You can always refund the noisemaker if it comes to that.
 
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#12 ·
A choke is a Good Thing if your car is driven on the street, especially if you don't live in the sunbelt. Especially if you're running an air gap manifold.
 
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#14 ·
huh?
 
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#15 ·
Milling the choke horn off a carb may not make the carb flow any more but there are situations where it is beneficial.

Cars with limited hood clearance that require the use of a drop base air cleaner benefit greatly from a carb with no choke horn. The reason is that the bottom side of the air cleaner lid is so close to the choke horn that it causes a restriction.

I do agree that today it is largely used as a marketing ploy. However, I would imagine this is why people started cutting off choke horns to begin with.
 
#16 ·
Tom Mobley said:
A choke is a Good Thing if your car is driven on the street, especially if you don't live in the sunbelt. Especially if you're running an air gap manifold.
Click to expand...
Not running an air gap, not sure about where the sun belt is (I'd guess Florida/Arizona?So Cal?) but I know what you mean....not having a choke makes my car tempermental until she warms up.

RatONaStick said:
Milling the choke horn off a carb may not make the carb flow any more but there are situations where it is beneficial.

Cars with limited hood clearance that require the use of a drop base air cleaner benefit greatly from a carb with no choke horn. The reason is that the bottom side of the air cleaner lid is so close to the choke horn that it causes a restriction.

I do agree that today it is largely used as a marketing ploy. However, I would imagine this is why people started cutting off choke horns to begin with.
Click to expand...
FWIW this is the carb I run:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY-0-82750&N=700+0&autoview=sku

They say it's supposed to help flow air better due to not having a big ol' choke tower in the way. Guess I would've been better off with this carb:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY-0-4779C&N=700+0&autoview=sku
 
#17 ·
I also run with out a choke. I have the air horn intact but the guts are removed. I live in So Cal so warm up to reasonably smooth operation is maybe 2 blocks on the coolest day. Secondary operation after a mile or so. Sooner than that and the engine bogs. A couple of ,iles and she's ready for full throttle beating.
 
Discussion starter · #18 ·
Thanks alot for all the great info. This site is the best website for getting information from people with experience in just about every forum. I'm going to try the secondary adjustment along with the wire trick and see how that works for me. I'll let you know how it goes when I give it a try. Thanks again. Gary
 
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Discussion starter · #19 ·
I'm getting ready to put the wire in the metering block but I'm not sure where the idle passage is. Can someone expain it in more detail please?
 
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#20 ·
can you post a pic of the front of the metering block?
 
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BlackBetty
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