Slight miss when cruising

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so i found another vehicle doing it... we just finished a 46 dodge with a 318/518 and we filled it up about a week ago and its doing the same thing, anything over 38* and it starts that surging BS.

Its our F**King gas...

now this not being my area im going to ask you guys, could the fuel be rated at 91 (or any octane) but have a lower "effective" octane due to the additives they add or removed for summer/winter blends? i would think not and that means they are selling lower octane gas for a higher price and that makes my blood boil. Any way to test octane at home?
 
I don't know of any lab testing that can be done at home, outside of simple mechanical testing done in an engine.

My guess is that the fuel is now being winterized, which may have an adverse affect on it's effective levels.

They use all kinds of stuff to bump the effective level of burning and detonation resistance. Gasoline is formed out of Heptane, Octane and Ethanol, as well as other components. Lead was a big one, but the fallout over cities kept it from continuing.

I highly doubt that in Phoenix, AZ you are getting much water in the tank, but you can always shake it in a clear bottle and let it sit, to look for separation. I've done that and I have a blacklist of gas stations that I will not go to, because of ground water content.
 
DaveBonds said:
I don't know of any lab testing that can be done at home, outside of simple mechanical testing done in an engine.

My guess is that the fuel is now being winterized, which may have an adverse affect on it's effective levels.

They use all kinds of stuff to bump the effective level of burning and detonation resistance. Gasoline is formed out of Heptane, Octane and Ethanol, as well as other components. Lead was a big one, but the fallout over cities kept it from continuing.

I highly doubt that in Phoenix, AZ you are getting much water in the tank, but you can always shake it in a clear bottle and let it sit, to look for separation. I've done that and I have a blacklist of gas stations that I will not go to, because of ground water content.
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well its 40% humidity right now but only 60* temp so there is plenty in the air to absorb.

bummer on the octane rating test...
 
Not sure what Holley 850 your running..... But if it has ajustable air bleed jets, Lower the mid-rang jet 2 jets and see if that help......

Just my 2 cents
 
dustya_383 said:
This happens right off the bat ... I'm running a holley mechanical fuel pump.. It does have the original fuel lines so the return is still there..
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Time to swap fuel lines from other car. Put 1/2 in Open spacer under carb, a wood or plastic one.
 
Also I wouldn't fill my car with anything but high quality gas...Shell first Cheveron second and maybe Mobil. NO Rotten Robbie or 76 unless its 100 octane
 
Increasing the size of the fuel lines? I don't think that could be the problem at all......if it were, you'd definitely know it at WOT. You're using a very small volume of fuel while at cruise. I think you may be experiencing pre-ignition, not a miss. I've replaced my spark plugs and gotten rid of this problem before. Couldn't figure out why, because the plugs I took out looked perfect.

I'd also back off the timing a few degrees right off the bat, just to see what happens too.
 
I have the same issue on my 84 D150 360, avanger 650 with vaccum secondaries, 3:23 gears. I have been tuning alot on the carb to get it to not hesitate/hiccup while cruising (drops a split second).. but can’t seem to shake it off. Sometimes when accelrating slowly it hesitates all the way up to rpm (mostly from cold engine). Also have the same hiccups while warming the engine up from cold-start. Should i back of the degrees or jet it up even more? Sounds clean when flooring it. Edit: You can also hear it stutter when i let go of the throttle at higher speeds.
 
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