de-tuning a carb
Thread Starter
Instructor
Joined: Jul 2006
Posts: 206
Likes: 0
From: Washington DC
de-tuning a carb
ok, sorry i don't know much about carbs, but i took my 6mpg to a shop the other day and they said that Ed Gaunt had it tuned pretty nice and it's running the way its supposed to be. They did however say there were two secondary jets (which dump extra gas in when you WOT) that were like the largest size you can buy a pair of 35's). They gave me a 28 and a 31 out of a holley they had lying around and said it should help with the driveability and fuel econ prob. My question is will this negatively affect anything? I'm assuming I'm going to loose some WOT power but quite frankly the tires wont stick the way it is now anyways.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
I assume these are shooters, not jets you are referring to since shooters come in that size, while jets don't. I have no idea who Ed Gaunt is so I can't say why he would put that size shooter on the carb.
Shooter are a tuning device used to address very specific issues. At that size, they would go along with a more agressive pump cam and 50cc pumps.
As to what issues they may be covering up for (which is usually how big shooters are applied), all I can say is to put the factory spec shooters on the thing and see how it does.
The shooters only come into play when you are moving the throttle open. They have no affect while cruising and, unless you monkey with the throttle a lot, they shouldn't have a dramatic affect of fuel economy. So even if the new shooters have no affect on how the car runs, you're not going to pick up fuel economy from your 6mpg to 12mpg.
Shooter are a tuning device used to address very specific issues. At that size, they would go along with a more agressive pump cam and 50cc pumps.
As to what issues they may be covering up for (which is usually how big shooters are applied), all I can say is to put the factory spec shooters on the thing and see how it does.
The shooters only come into play when you are moving the throttle open. They have no affect while cruising and, unless you monkey with the throttle a lot, they shouldn't have a dramatic affect of fuel economy. So even if the new shooters have no affect on how the car runs, you're not going to pick up fuel economy from your 6mpg to 12mpg.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 206
Likes: 0
From: Washington DC
yeah it was the shooters, that sounds familiar. My bro says the guy has it setup for track which is why he put two 35 shooters in it, its setup to run WOT more than not hehe. The problem me and my bro are trying to address is not only fuel econ, but hesistation when you WOT (engine nearly floods out), and dieseling when turning it off.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Sounds like someone thoroughly screwed up your carb or you have a bad combination or some mechanical ills. It would be hard to tell you where to go if you don't have some basic knowledge other than your car is baaaad.
Melting Slicks
Joined: Jun 2001
Posts: 2,265
Likes: 549
Take your list number off the carb and look up what holley wants for jets and power valves. That would be a good first step. I don't think your shop wanted to mess with it. A mileage complaint is something most shops shy away from. Ron B.
Racer
Joined: May 2005
Posts: 470
Likes: 1
From: Amelia Ohio
If it has vacuum secondaries you can change to a stiffer spring to slow them opening for better fuel economy. If it is running and tuned right I would change anything else except for installing an OD trans.
Chris
Chris
Melting Slicks
Joined: Jun 2001
Posts: 2,265
Likes: 549
I just checked your profile and see you have a BG carb. You will need a wide-band to tune it right. Order up both sizes of air bleeds. And you will need a set of numbered drill bits. I am running a RS 825 race demon if its like mine it is pretty close WOT. But mid range, off idle to 3000 RPM it is rich under light throttle. You need to cut back the IFR and go from there. To get it right you will need a wide band. I will never regret spending the money for my LM-1. It is the only way to get it right. Most people just give up and bitch at this point. But they are a great carb once you know where you are at. Ron B.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 206
Likes: 0
From: Washington DC
cool thanks, good tip! 
I dont think the original owner complained about the fuel econ, but he has everything setup pretty much for track, so I think fuel econ was something he probably told the builder not to worry about. I took it to another carb shop here and they told me its running pretty much the way its supposed to run, 500 hp is expensive hehe.
I dont think the original owner complained about the fuel econ, but he has everything setup pretty much for track, so I think fuel econ was something he probably told the builder not to worry about. I took it to another carb shop here and they told me its running pretty much the way its supposed to run, 500 hp is expensive hehe.
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