Thread: engine stumble trouble

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I'm having problems with my engine stumbling. It gets worse the longer I drive it. I replaced the plugs and have noticed better performance but did not resolve the problem. I'll check the carb and intake bolts this evening to rule out a possible vacuum leak, I have done this before and i don't think that is the problem either.

I'm hoping you will tell me its possibly due to the timing. I have a buddy coming over next week to check that as well as the vacuum.

Can't wait till the end of August when I'll pull the engine out and start fresh.

Originally posted by Streets
[B]Ruling out vacuum leaks:
Cover the top of the carb, spray ether on all connecting surfaces, lines, hoses, and listen for any change in rpm...

At night time, raise the hood and while running the engine at all different rpm's check to see if any wires are arcin' or use a timing light hooked to each one in turn..

What exactly does the ether do to indicate a leak? is there anything else i could spray on it if I can't locate a can of ether?

As far as the arching goes, I'm assuming I would see a spark jumping off one wire to another?

Another thing while I'm here:
I'm running at about 2700 rpm's at 40mph. Why in God's name are they so high?

it's a Chrysler 440 with a 750 edelbrock carb, performer rpm intake, headers, 3.23 rearend, 14" wheels, and fairly beefy cam. But i'm sure i shouldn't be running that high. Any tips on adjusting and tuning? Or what could be contributing to it?

Usually when an engine stumbles during the transition from idle to acceleration, its either a problem with the accelerator pump or a problem with the primary power circuit (I know Q-Jets use a spring, Holleys use a Power valve, I dont know what Edelbrock uses).

Check your vacuum at idle and buy the approriate power circuit spring/valve.

If it BOGS, then its your timing.

Are you running points ignition? Check to see if your points are pitted, or better yet spend the 10 bucks and change the points and condenser.

As for the RPM at 40mph, this is a result of gearing and has nothing to do with engine tuning. If you want it to rev lower, change the differential gears for 3.08's (at the cost of acceleration) or upgrade to an overdrive transmission. What would be even easier, just buy larger diameter tires..... You know old muscle cars look uber-cool with 17" Torque D's.

EDIT: Are you sure youre running 3.23's? That speed doesn't make sense with 3.23's unless you have a tire diameter of 18". Verify your diff gearing.

It more or less chokes and stutters when accalerated. It go's at first then coughs a few times on and off. I'm going to replace the plug wires soon. A couple of wires rest on or near the headers and one boot has been toasted. I tried wrapping some therma shield to help protect it.

I'll look into the primary power circuit once I figure out what it is, where it is and what it looks like.

It's an electronic ignition and I'm 90% sure it's a 3.23 but will investigate further. the rims are 14" and the tires are 225/ 70 R14.

Very interesting, thanks Streets.

i had some what siilar problem on a trip to colorado in my 67 camaro 396 its a new carb and all and up here in sd ittl lite the tires throuh 3rd gear from dead stop in drive ..its an auto ..for now lol and when i got to colorado it would sputter and almost die on hard aceleration then it would take off and bam all the power in the world...i belive my problem was my carb is jetted for south dakota ellevation and the increase in height in co and less air led to my problems cuz when i got back to sd it runs like a champ again ...not sure if this helps at all ohh and ps my timing was dead on were it should be well good luck

I had the same trouble with my carb, the secondry floats were to hi. if you can close your air fuel jets and it still idles, you are getting fuel from some other place,and then when you step on it you get an over load. i would get a backfire if i stepped on it to hard,or it would bog down. So thats my two cents worth.

If the plug wire's are shorting out that mean's you're not running on all eight cylinder's . Address each area seperately ignition , fuel which include's any vacuum related problem and also check contaminants in the fuel , filter's if you have a holley check the bronze filter's in the inlet.

What kind of carb are you running? If it'sa Holley, you are starving it or drowning it.

Shaggy