Why is my engine doing this?
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Fleet Mechanic
Joined: Jun 2007
Posts: 1,931
Likes: 2
From: Ohio
Why is my engine doing this?
I'm posting this in here because I don't really thing it's engine specific. It is a 390 in my F100, stock ignition set to 10btdc and 36degrees total around 3000rpm, edelbrock 600. I may have asked this question on here before but I forget now. When it's idling at running temp, if I push the gas pedal to the floor, 9 times out of ten, the engine will "pop" (sounds like when you flick your finger at a paper bag from the store. It's not loud, but noticeable) and drop a few 100rpms for a second, then idle back up to 800 where it's set. What the hell is causing this? Would it be from the vacuum advance advancing the timing too much too soon?
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Fleet Mechanic
Joined: Jun 2007
Posts: 1,931
Likes: 2
From: Ohio
Well I went and started it up again 10minutes ago and fully let it warm up. Kinda forgot that it's cold out now and it doesn't warm up as fast, and the first time today i didn't let it run as long before I thought it was warmed up.
Well it didn't do that out of like the 8 times in a row I tried flooring it from idle. It revved nicely no problems. I also set the mixture screws both 1/4 turn richer. Maybe that did something? Or maybe i just let it warm up more?
Well it didn't do that out of like the 8 times in a row I tried flooring it from idle. It revved nicely no problems. I also set the mixture screws both 1/4 turn richer. Maybe that did something? Or maybe i just let it warm up more?
Lead Driver
Joined: Mar 2004
Posts: 8,924
Likes: 153
Maybe the advanve plate bushing is wearing out. I'd tear the dist. down and look it over. I would try to get all the advance is quicker, the sooner the better. How soon would depend on just where you run into detionation. Make sure the limiter is in the short slot and remove the one heavy spring and put another light one in place of it.
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Fleet Mechanic
Joined: Jun 2007
Posts: 1,931
Likes: 2
From: Ohio
Yea I've switched out the heavy spring already. It's a remanufactured duraspark I bought a few months back. Vacuum advance is on the timed port. Like I said it didn't do it at all when I had let it warm up more, but that might have just been a coincident.
More Turbo
Joined: Nov 2006
Posts: 538
Likes: 11
From: Great N/W
Doubtful it has anything to to with the dist., it takes a second for the dist. to react from depressing the accel. off idle Your idle misture screw adjustment MAY of helped, but only in the smallest of amounts. An off idle 'pop' is usually a lean condition. I would richen up the accel pump, I'd bet that'll fix it. On a side note, I'm sure there are many fans of the Edlebrock carb here, but I personally have had nothing but bad luck with them. Gimmie a Holley any day of the week !!!
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Cargo Master
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