Just another carb thread....
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Elder User
Joined: Apr 2015
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From: Boston, KY
Just another carb thread....
I just rebuilt my 460 with an RV cam, 0.03 over, edelbrock RPM intake, and a 1406 carb.
The truck has plenty of ***** accelerating from a stop and zipping around in 2nd and (most times) 3rd gear at relatively low RPMs. It's when I am trying to accelerate up to highway speeds at full throttle that this gem turns into a turd. If I am trying to pass somebody on the gentlest of uphill slopes on the interstate, I need to plan on it taking about 5 minutes in overdrive. Sometimes I have my foot to the floor and slowly lose speed uphill in 5th. This is doing about 75 mph so I am hesitant to downshift. It seems like it takes forever in the upper end of 3rd and all the way through 4th to accelerate.
Long story short, I think my rods/jets and maybe springs need adjustment. Is there any way I can determine whether I need to go richer or leaner, other than by trial and error? After reading the manual, I think I need to go richer or leaner on the power mode while staying the same on the cruising mode. (#2, #3 or #5 on the calibration chart)
Fuel pressure, A/F mixture, idle speed, etc are all squared away.
The truck has plenty of ***** accelerating from a stop and zipping around in 2nd and (most times) 3rd gear at relatively low RPMs. It's when I am trying to accelerate up to highway speeds at full throttle that this gem turns into a turd. If I am trying to pass somebody on the gentlest of uphill slopes on the interstate, I need to plan on it taking about 5 minutes in overdrive. Sometimes I have my foot to the floor and slowly lose speed uphill in 5th. This is doing about 75 mph so I am hesitant to downshift. It seems like it takes forever in the upper end of 3rd and all the way through 4th to accelerate.
Long story short, I think my rods/jets and maybe springs need adjustment. Is there any way I can determine whether I need to go richer or leaner, other than by trial and error? After reading the manual, I think I need to go richer or leaner on the power mode while staying the same on the cruising mode. (#2, #3 or #5 on the calibration chart)
Fuel pressure, A/F mixture, idle speed, etc are all squared away.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 38
From: EXTREME southwest CT
You say mixture is "squared away" but you want to change the jetting???
Personally I think you have a cam and/or ignition timing problem, not a carburetor problem.
ETA: Perhaps a 'towing' cam would have been a better choice for, towing.
Installing springs and checking pushrod length is not a big deal.
Personally I think you have a cam and/or ignition timing problem, not a carburetor problem.
ETA: Perhaps a 'towing' cam would have been a better choice for, towing.
Installing springs and checking pushrod length is not a big deal.
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
Yes it could also be a timing issue. Remember everything has to work as a "team".
As for seeing if you need to go rich or lean on the high speed side of the carb you need to pull the plugs and look at them.
You need to get it up to speed at WOT, turn the key off with foot still on the floor, cost to the side of the road and pull the plugs for a look see.
Yes it is tricky to do this safely.
Lean plugs will look new, clean, white.
Rich plugs will look black.
What you are looking for is light gray plugs. You may have 1 or 2 plugs light in color but most should be gray.
And yes you will also have to "play" with jets/rods/springs and pulling plugs.
Once you have a good A/F ratio you might be able to put more timing into it.
Dave ----
Lead Driver
Joined: Jul 2011
Posts: 8,678
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From: On the Edge of the Desert
1406 has a lean calibration out of the box. It's meant for best MPG.
But it doesn't sound to me like a carb problem either.
What transmission/gearing do you have? What RPM are you at trying to go up hill in OD?
But it doesn't sound to me like a carb problem either.
What transmission/gearing do you have? What RPM are you at trying to go up hill in OD?
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
Dave ----
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Elder User
Joined: Apr 2015
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From: Boston, KY
Performance seemed to be getting worse and worse with each trip. I got home with the truck still running yesterday, went to check timing, and sure enough, the hold-down bolt had come loose and I was at 0* with the spout connected. Rookie mistake! I would still like to get the carb fine tuned and make sure I have the ideal springs and rod/jet combo.
I recently rebuilt the engine and am still trying to get a feel for how everything performs. I still don't have a good baseline to go by yet.
I recently rebuilt the engine and am still trying to get a feel for how everything performs. I still don't have a good baseline to go by yet.
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