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Old 05-15-2004, 11:15 AM
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still an off-idle stumble

After months of trying to cure this stumble, i have finally come to one conclusion, its the cam. I've played with the timing all I can, tried 3 different carbs, 2 holleys and a edelbrock. Put bigger squirters on the 3rd holley still didn't fix it although it helped a little. The truck has a 2k stall and 3.73 gears with small tires.

Its the GM LT4 Hot Cam.... is anyone else here running this cam or have any experience with it?

GM says the powerband on this cam is 3000 - 6500 RMP?!? 3K? Isnt that a little high? Here are the specs I found for this cam:

204/214 @ .050 w/ 1.5s
.525 lift 112 deg

Any advice is greatly appreciated

Thanks
Sean S.

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Old 05-15-2004, 11:38 AM
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Give it more initial advance and less distributor advance. That in itself will cure a little if not all of the bog. Just turning the distributor and changining the timing using the light wont do it. You have to recurve the distributor.
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Old 05-15-2004, 01:01 PM
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OK i got a curve kit and set it at 22 initial and 34 total advance. However it still has that stumble. Even if i'm cruising at 3000, if i give it like another 1/8 - 1/4 throttle it will stumble then pull, sometimes it has a little backfire thru the carb. It even has that stumble if your cruising at 4k and lightly tap it. even though i don't ever cruise at 4k.

thanks
sean
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Old 05-16-2004, 10:10 AM
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Today I took off the distributor cap to check things out. When I was looking at the cap, I noticed something. Now bare with me, i don't know terms. The 8 little metel electrode things inside the cap looked funny. They had marks on them from where they are firing with the rotor, but for some reason the mark is only on half of them, on a particular side. I looked at an old Accel cap i had and the 'sparks' are centered. Could this be causing a hesitation? If so what causes this mis-alignment?

Thanks
Sean S.
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Old 05-16-2004, 04:42 PM
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if the inside terminals are burnt off of the center alittle then the timing is off.and replace the cap and button.the stumble is weird,i had it on a 350 and it was the carb float was to low but this was only on a start not when rolling past 1500 rpm.call holley tech line they usually know what there talking about.
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Old 05-16-2004, 07:23 PM
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Have you tried a different accelerator pump cam? Make sure that there is no slack in the pump actuator anywhere. Don't make it tight, just take up all the slack.

On the recurve kit you got, which springs did you use? I used one gold and one black to get the rate that I needed. Get a new dist. cap and rotor. Yours is off center.

Have a look at the acc. pump cam and actuator first. It sounds like your not getting enough from it.

Larry
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Old 05-16-2004, 08:31 PM
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I went from a #28 squirter to a #35 squirter. It helped a little. The accelerator pump actuator is adjusted correctly. I guess i need to change the pump cam? If so what do i change it to? I've never messed w/ that thing.

Thanks
Sean
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Old 05-18-2004, 12:30 PM
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SO I've been pondering about this cap issue. So what exactly would _cause_ the cap/rotor to be 'off center'? Could it possibly be the crappy wiring in the truck delaying the spark or signal? Just trying to understand whats going on. Any help is greatly appreciated.

Thanks
Sean S.
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