sputtering

[Kevin Alexander]

I have been chasing a sputtering problem with my motor for a while now. What happens is when I am running a constant 65 or 70mph for 10 or 15 min I get this crackling sputtery sound from the motor. Sounds just like a linkage that isn't right or an idle jet stopped up. However you can slow down to 55 or so and its as smooth as glass. I can run 70mph and for the first 5 or 10 min its smooth and no issues but any longer after shes warmed up a little it starts acting up.
I have tweaked the linkage till I am blue in the face and no jets are clogged. Is this symptoms of the motor getting hot and misfiring? My oil temps are ok since it has cooled off outside but that dont mean the heads arn't hot.
What do you think??
Oh and when this is taking place you can put your foot in it and it pulls like a raped ape.

2332, 10.3:1 comp, 44x37 wedgeports, 86c cam, 32deg timing, 1 5/8 header, 44 idfs w/38 vents, 160 mains, 57 idles, 175 airs, stock doghouse cooling system with decklid propped top and bottom, 93 octane pumpgas.

[Clinton DdK]

What rpms are we talking? You might be right in between the idle and main circuit change over.

[KAFUR1]

when was the last time you cleaned you fuel bowls in your carbs?

[John P]

Is this new (meaning that it ran great before) or has it always been like this?

[Bluesman]

Loose heads?

[R SEIDCHECK]

try 200 airs.

[ALB]

Gene Berg used to say that if it runs great cold but not quite right warm then it needs to be a little richer. How does it run with a one step bigger main jet? But before you do that, how does it run with only 28-29 degrees advance?

[maui]

I would say check your screen in the gas tank. If it was 48s then I would say bigger idle jets.

[Kevin Alexander]

It is doing this around 3000 rpm. It has always done it since I built the engine 5000 miles ago. I tried 200 airs and still the same thing. I also tried a 165 main and it still does it but the motor seems heavier as in too rich. I have been wondering since I am at 10.3 compression and running 93 octane pump with the web 86c that maybe i am on the edge of being able to run pump gas and the motor isnt burning fuel correctly when hot. Ever since they went to 10% ethanol here in GA everything I own runs worse and my truck went from 19mpg to 17

[Clinton DdK]

2800 to 3000rpms is right on the point of transfer between the idle and main circuit. Try a bigger idle jet or go a little faster. Do buy your gas at the same place. I had a problem once with my Z71. It started running like dog poop. I use to get my gas right down the street from work so I decided to change gas stations. Problem went away. My co-worker use to blame this same thing on Ethanol and used this gas station as an example because everyone he know who was having problems with their car was getting their fuel there. He claimed that when they pulled there plugs there was build up on them and said that was from the Ethanol. I know that the Speedway stations around here in Michigan is 10%. I aways try to get my gas at a speedway station. I just did a plug change in my little truck with 110,000 miles on it and had the factory plugs in it and the plugs were clean.

[Kevin Alexander]

I will try a 60 idle then. I thought it could be lean on the idle circuit because when the engines cold it idles at around 500-600 and sounds like its going to quit. Let it idle for 5 minutes or drive it a couple miles and it idles at 1000. Could this be too small of an idle jet?

[maui]

Usually it would sputter or hesitate under slight load and lower rpm range. When going up a slight hill it hesitates and loads a little, engine temp gets hotter than normal. This is the symptoms that I noticed with mine when idle jets are small.

[Cave Man]

Well my 2110 has about the same issue. Kevin got into the 44's on it and they have 50 idles? Same issue when running along at 2000 ~ 2800. Then it comes on good at about 3000 on to 6500. Gets hot unless you Idle or beat on it. Getting some 55 idles to try.