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i went out cruising last night and got in a bit of a race with an LS1, well anyway we're going and i hit about 4500 rpm in second and the car begins to choke and stumble, so i shift into third and it does it again right at 4500 rpms. I took it out again this morning and it's still doing it. I had this same problem about a month ago and it turned out to be the coil. I went ahead and changed the cap and rotor along with the coil(wires were already almost new), and the problem went away. Well recently i changed the secondary metering rods and played around with some other things on the carb, and for a while it was pulling HARD all the way to about 5500~ rpms. Now it's stumbling again. Would fouled out plugs cause this? Should i step up to a bit hotter of a plug? I have autolites in ther now, not sure of the part number cause i didn't put them in, but could anyone give me a recommendation on a good all around plug, possibly one that burns a bit hotter? Details on the engine are below, let me know if you need more details...
I'd go out and check to see if they are fouled out myself but it's kinda snowing right now,,, and the garage is unfortunately full of Hondas and Fords....

Eric

Gm350 "010" block,crane 272H cam, Edelbrock performer intake, SMC tuned non cc Qjet and Dist, SMC custom cold/ram air intake, Edelbrock headers and catback, MOROSO 8mm wires, T-5 w/ Hurst billet shifter chopped 1", 3.23 open rear, hatch mount battery, 4th gen Firebird interior, Autometer guages, RJS belts, new hugger orange paint. IROC rims, Goodyear GSC's, some other stuff. 14.59@95.6 last summer. hoping for 13's opening night Feb 22

 

Replaced the fuel filter lately? I would think if the plugs were fouled that you would have a miss @ idle.

Do you have the Goodwrench 350. I'm probably going to do a cam swap and was wondering if you ran your car w/ the cam that came in it before you got the Crane one. If so, how much difference did you feel?

 

the filter is about a month and half old, but maybe i'll change that anyway. On the other hand, maybe it's just bad gas. I got gas at a WAWA convienience mart, and that seems to be about when the prob started.

As for the motor, it's not a crate motor, it's just a GM 010 block 350. with a 272H cam. I thinking of upgrading the cam myself cause im not all that impressed with it.

Eric

 

i pulled one of the plugs today and it looked perfect, no carbon buildup, gap was correct etc... so i don't think its the plugs.

I checked the fuel filter and it did look somewhat dirty so i replaced that. I haven't driven it yet though so i don't know if it solved the problem. I doubt it did though.

Now iim starting to think it might be the Advance Auto coil i bought about a month ago. How can i test for a bad coil?

Eric

 

Keep me posted on this, I have exactly the same problem

 

Hey guys I had the same problem. Check this sites. I did it to my non computer carb and it fixed the problem.

https://www.thirdgen.org/newdesign/tech/quadrajet.shtml

 

It may not be the plugs but it certainly could be even if they look great. How old are they? They aren't expensive so buy a set of AC's and change them, can't hurt. I have seen plugs cause high a rpm miss before. I couldn't hardly believe it was plugs, my buddies car would start popping and missing at high rpm and that is all it was.