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Discussion Starter #62
bet when you put on the single plane, you'll have to back out the screws a little, yeah it makes a differance. and you are prolly going to have to rejet too. The dual plane just creates a stronger signal at the carb.
We'll see how that goes. All I have on there right now is a performer 2-0 so hopefully a new intake will help the issue. I'm debating between a dart single plane and a dual tunnelram. I guess that's a whole new can of worms :D

It was worth a try!
 

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It's what we do
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I hope we know a little more about carburetors today than we did in the "early 70's" :D:D:D:D
Read it again. Thats when I started experimenting with Holley's..... and your right, and after over 30 years we know a lot more today. You guys have fun debating, I've got work to do.
 
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Discussion Starter #65
Have you got it figured out yet?
Nope,
You wana help me decide? A friend offered me a polished Weiand TR with a Dooley scoop for $350. I already have the carbs but they need to be rebuilt. Or I can take the Dart single plane for about $300 and I have this fresh rebuilt 850 to slap on top. May I present, my dilema... :D
 

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Read it again. Thats when I started experimenting with Holley's..... and your right, and after over 30 years we know a lot more today. You guys have fun debating, I've got work to do.
Thought maybe you could explain what was happening.

Not really debating, just trying to explain what circuits do what. It is all pretty simple. Like what has been stated by a few during this, if the powervalve rating is affecting idle AFR there is something else wrong.......that's all. ;)
 

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I think it has been very well explained but to add my recent experince to this. I just built a 350 ci motor for my chevelle and the car would not idle for beans with the same carb and set up that was on the stock 350 motor. It was always dead rich at idle and cruise on this new motor, and I tried every combo of jets I could imignine. Then thought of the PV and measured my vacuum. Turns out I had only 6 inches at idle and the PV was a 8.5 Bought some PVs lower than 6 and walla, brought the air fuel ratio both at idle and cruise right on in according to the wide band O2 meter!!
 

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The fact that it fixed your cruize is exactly what the PV is suppose to do. The fact that it fixed the idle isn't. If the power valve is wide ass open the main well/circuit can only see this as a jet increase of 6-10 sizes, the PV channel goes straight from the PV to the main well. So your saying that jetting up will affect your idle. Thats never happened to me. So I have to believe some thing else is affecting the idle when made the change, gasket leak or small pin hole in the diaphram?



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E-7 Sheepdog (ret)
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Nope,
You wana help me decide? A friend offered me a polished Weiand TR with a Dooley scoop for $350. I already have the carbs but they need to be rebuilt. Or I can take the Dart single plane for about $300 and I have this fresh rebuilt 850 to slap on top. May I present, my dilema... :D
The Dart and the 850, but it'll cost you at least 15 bling MPH.
 

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you'd be asking the wrong guy here. I have no need for single plane except they are cheaper. Have yet to find one that I could get to work worth a shit without way more work than it was worth, only to find out I could make more power, over a wider range with a decent tunnel ram and do it way easier. You just know I opened a can of worms with that statement!
But have just given up on them, just don't have the patients for em



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Discussion Starter #72
you'd be asking the wrong guy here. I have no need for single plane except they are cheaper. Have yet to find one that I could get to work worth a shit without way more work than it was worth, only to find out I could make more power, over a wider range with a decent tunnel ram and do it way easier. You just know I opened a can of worms with that statement!
But have just given up on them, just don't have the patients for em
Just when I was leaning to the single plane you hit me with a left....
 

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I had the same problem on my 850 carb, my idle was too high & it was dripping out of the booster sometimes, it was just on the edge of the idle circuit & main jet curcuit .when i blew my pv it ran way fat at idle ,missing etc. could have been because it was running past the idle curcuit being on the edge. . i set the idle down . here is some info that helped me, they also helped me boost refrence my 850 myself,i am running 2 power valves also.
from the holley site:
(The idle system supplies the air/fuel mixture to operate the engine
at idle and low speeds. Fuel enters the main well through the
main metering jet that is screwed into the metering block. Some
of this fuel is then bled off to an idle well where it is mixed with
air from the idle air bleed hole. The idle well leads directly to the
idle discharge port and the idle transfer system where this air/fuel
mixture is discharged.
Most Holley Street Performance, O.E. Muscle Car, Competition
and Pro-Series HP carburetors utilize idle mixture screws, located
on the sides of the primary metering block. These control the volume
of the pre-mixed air/fuel coming through the idle well.
Turning the screws clockwise will “lean” the idle system.
Conversely, turning the screws counterclockwise will “richen” the
idle system.
The initial adjustment is made by turning the mixture screws in a
clockwise direction until they lightly bottom. Back them both off 1-
1/2 turns. Connect a vacuum gauge to a carburetor vacuum
port that will have access to full manifold vacuum at idle. Start
the engine and allow it to warm up. Once the engine has
warmed up and the idle stabilized, the choke should be disengaged.
Adjust the idle mixture screws to obtain the highest vacuum
reading. Each screw should be turned an equal amount so
that the system is balanced.)​

From a holly rebuild book:
(No more than .040 to .060 of transfer slot should be showing on the primary side. if opening the secondary idle stop doesn't corrrect the problem you may have to drill a 1/16" or 1/8" hole in the primary butterflies .)

By the way, your power valves are 6.5 ,what is your vacuum? they say choose a pv that opens 2-in (hg) below your lowest steady cruise reading for cars & 2in(hg) below idle reading in gear for auto trans. on race engine with hi overlap cam, high idle deal hope the info helped.
 

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IMHO, if a person has trouble tuning a carb on a dual or single plane intake, then that person will have more trouble with a tunnel ram.

Engine Parts and correct installation is only part of the equation for driveability and hp. Tuning is the other part.
 
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Discussion Starter #77
IMHO, if a person has trouble tuning a carb on a dual or single plane intake, then that person will have more trouble with a tunnel ram.

Engine Parts and correct installation is only part of the equation for driveability and hp. Tuning is the other part.
Tunnel Ram it is! :D
 

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IMHO, if a person has trouble tuning a carb on a dual or single plane intake, then that person will have more trouble with a tunnel ram.

Engine Parts and correct installation is only part of the equation for driveability and hp. Tuning is the other part.
In some respects I couldn't agree more. If you don't know your way around a carb, a tunnel ram may not be the place to learn, but I have torn my hair out trying to get single planes to work the way I'd like and have come to the conclusion that they are what they are, and trying to make them something else is is either insane, stupid, or at the best, very difficult for those more talented than I at getting them right. Everytime I give up and put on a T-Ram, I have to ask myself why I even tried with the single plane. But they are truly excellent for the intended usage, max horsepower UNDER THE HOOD. Thankfully, my boat doesn't have a hood.:)



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