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Hey, I have a 79 and it has a miss between 2000 and 2600 rpms. I have replaced the plugs, plug wires, points, cap, rotor and the timing and dwell are dead on. Could this be a carb problem? Is there another fuel filter besides the inline right before the carb? The truck runs great at all other rpms. Help Please!

I also have a 79.

Yes, there is another, unless it's been removed. It's on the driver side, just in front of the rear wheel, on top of the frame. Mine had been replaced with a filter that had straight inlet and outlet ports. I got one that had straight inlet port, and a outlet port that was at 90 degrees to the filter. Check FRAM GA3. I didn't write it down, but I think that's it.

If you still have the electric fuel pump, it is located underneath the truck, hidden in the cross beam between the frame rail. There is a fuel filter in there also. It is replaceable. I have several posts with more info. Make sure you disconnect the battery before doing any electric work. Also, if you suspect the fuel pump, you can test the output pressure before you replace it. Might save you $60.00-$80.00.

Last, and totally not related to the above, and ONLY because we are discussing a '79, pay close attention if you ever feel the need to replace the voltage regulator. All the pictures on web, and even Auto Zone, will pull up a VR with a rectangular plug. If your's has a rectangular plug, great. If not, it will probably be round, and that comes from a 1980.

I'd like to know if you eventually find the miss, and what you did to solve it. I have had a low rpm miss (850-1500)since I got the truck.
Here is what I have done, but it wasn't trying to solve the miss. It's just that the miss did not go away:
All new fuel filters(including the pump, I have three); fuel pump; electronic ignition; new plugs, wires and coil; Weber carb; all emissions removed.
Good luck, welcome, and let us know.

Is it missing at the same r.p.m.s in every gear? I dont think it's a filter problem because it would continue to miss beyond 2600 r.p.m.s.
Are you running a stock carb?
The only thing left on the ignition to check is the mechanical advance. Maybe it's binding up as you accellerate. It should work smoothly throughout the r.p.m. range. At 2600 r.p.m., the weights are being flung hard enough to free themselves.
It's a shot in the dark but i doesn't cost anything to at least check it.

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
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Thanks for the info "Blue Meanie". I forgot to mention in my first post that it only misses when I let off the accelerator. Once I start giving it more throttle the miss goes away. But it does only happen between 2200 and 2600 rpm. Thanks for the help

it may even be the vaccum advance on the dissy, im not to sure how to check it tho. or even a bad connection with the condensor or wire to the dissy. just an idea

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To check vacuum advance, pull the vacuum hose off the manifold and take the distributor cap off. Suck on the vacuum hose and the breaker plate should move. If you suck air through the hose, then the diaphragm has a hole in it that shouldn't be there.

Just wondering if you found the problem? I have a simular situation. My 79 started to do this in 4th at 55mph. Now it does it thru all gears at the top end. I've pretty much replaced all the electrical except the wiring. Regulator, coil, points/condesor...etc.. It has dumfounded me. The fuel pump is almost a year old. I have a weber with a fuel pressure regultor. I'm taking it in to a mechanic to have the head gasket done because I have a slight leak. And want him to look at this problem. I'm also going to order an electronic ignition kit.

With a mid range miss the vac. is advanced and what you have is a timing miss (to much)and when you step on the gas it drops some of the vac. adv. and is smooth again.

Check timing if it still persist try disconnecting the vac. hose to the dist. and i bet it gets smooth again.

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

i was once told that the teeth were about 1/4 - 1/2 off from the chain and at higher rpm it might be pulling ti fast enough to skip a link. dont know if its true but just something i heard. also if you put a MSD box in it i have read all over this site it takes a high rpm miss out... just a couple penny's worth

Chris

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76' stepside mikado w/sunroof

Agree with tj, running rough mid range rpm light throttle is timing advanced too far.

It does it with the vacumm adv on or off. That was my first thought. Now I was told by webber when putting the weber in that the timing was to be set at 12-13 degrees, I'm at about 12. I think on a factory carb it is like 6. I'll try backing it off.