c3 engine stutter

hey guys, this is my first post to this group but ive seen a lot of good things and knowledgable responses so i wanted to post. I have a 79 L48 w/
edelbrock intake and 3/4 cam , weber carb. I dont know specs on cam as it was installed by previous owner. Anyways the car runs/ looks great with the exception of whenever i give hard acceleration or a steady acceleration between 2nd to 3rd or 3rd to 4th , if i let the rpm go over 4000 rpms the engine stutters and acts like it drops a cylinder. When you let off the accelerator and shift, it accelerates fine until i hit that 4000 mark again. Mind you I dont make it a habit of pushing the engine that hard but its just one of those things that drives me nuts. Ive replaced the plugs and wires ( plugs looked fine btw) the weights in the advance are fine, the only thing i havent looked at is the fuel system , tho after reading a post here about a stuttering 69 i may. any thoughts? Larry in Va Beach
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Larry & Michele wrote:

Since several private forums like JLA Enterprises have begun copying all we say and do on alt.autos.corvette and getting their piece of advertising dollars for it, while we the originators of the information get nothing, several have begun to migrate away from here so you may not get a lot of helpful answers. So to JLA and the others like them I say...
FUCK OFF!!!
Having said that, there could be multiple reasons for your stutter. It could be fuel, ignition, or valves float due to improper valve lash or a bad lifter or two (not likely, but possible, besides it would make lots of noise and run very badly at idle, if this was the case). Sounds as if you already ruled out ignition, so fuel delivery is the next more likely cause. Fuel filter, vacuum leak, carb adjustment. I'd start with those first, then move to the more expensive, more difficult possibilities. Are you sure it's a Weber Carb? I can't say that I've ever seen a single Weber carb for a small block, or a big block for that matter. Is it one of those nifty multiple two barrel setups, or what?
TomC '90 ZR1
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yeah, im sure its a weber lol..obviously an aftermarket setup from previous owner and yeah its multiple 2 barrell with adjustments for left and right. I had one guy mention valve float before and i guess my only thing is , is if the lash was loose enuff to float a valve, wouldnt ya hear a rocker arm clatter? larry

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has the distributor cap been replaced recently? Could be corrosion induced crossfire.
Larry & Michele wrote:

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valve float
Is a phenomenon independent of stem-rocker clearance. Valve float occurs when engine rpm is high enough that the force of the valve spring is insufficient to overcome the inertia of the pushrod and lifter and keep the lifter in contact with the cam lobe. Early roller lifters did not have guides to keep the rotating center of the roller aligned with the centerline of the cam lobe. As a result, the lifter could partially turn in the lifter bore. It turns out that a roller lifter turned sideways on a cam that has a really steep opening ramp is a bad combination and usually made really expensive noises when everything started coming back in contact again. Modern engines have indexing guides to prevent that.
Charlie

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H'm, I had a very similar problem in another car once - ignition got raggedy and "broke up" over a certain RPM but everything checked out fine in the garage. Turned out to be a badly routed ignition primary wire that was creating an induction misfire over a certain RPM.
-- Vandervecken

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I had the same problem with my 74 L82, after doing a fuel pressure test we found out that the pump was only putting out 3.5psi and the specs call for 7-8psi. Replaced the fuel pump and the problem was solved. good luck

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On Sun, 08 May 2005 21:36:57 -0500, Vandervecken

this problem in the tach needle, bounceing or fluttering, jumping around somehow. I would key in on the fuel delivery like you suggested on your first post. And to chime in with the other fuel suggestion, test for the pumps delivery volume as well as pressure, with two carbs to feed volume might be a problem that is hard to detect. I would also be interested in how the power valve(S) were set up and functioning inside the carbs. Was this car tuned at a high altitude by the first owner and then you bring it to a much lower alt.? If the engine was dialed in for high alt. It might be running lean all the way around. Good Luck

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You're right about the tach. Good point.
-- Vandervecken
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