chev 350 studders under a load?

My 46 started to studder yesterday while under a load! It free revs fine but.. under a load it seems to be missfiring or be starving for gas! It has new plugs,wires,cap,rotor,(hei) new electric fuel pump! It doesnt have any vaccum leaks! Anyone ever had this happen to them or... Know what it could be??


Cheers,

Rich

 

Did it start acting up before or after you installed the new parts?

how's the fuel filter? tank? etc

 

does your engine have an EGR valve in the manifold?? If it does check to see if it has vacuum after it's warmed up... it shouldn't ...If it doesn't have an EGR maybe the cam is flat on intake??? ugly thought but a could be...Good luck on the problem !

 

Before... Maybe the coil on the hei?

 

Usually there is no "inbetween" on Hei pieces. either they work or they don't but it wouldn't hurt to check the coil and see if it is starting to break down.
Have you checked the vacuum advance? Pop the hose to the advance off at the carb end and suck on it to see if the diaphragm is good or not.
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Oh, HEIs can be as intermittent as anything else. One time I replaced a module and missed when I plugged the pickup coil onto it....that was fun to figure out....the terminal made contact most of the time.

 

Intake manifold leak has done that to me before.

 

Lots of possible causes. If it does the same thing all the time, it's probably not a fuel supply issue, as that would cause it to act up only after it's drained the float bowl. Plugs, wires, flaky coil/cap/rotor/pickup/module, cam/valvetrain problems, etc are likely candidates.

Look for "made in china" parts that you installed first

 

I had a hairline crack in a sparkplug, would Idle great but in motion was arcing out. just a thought

 

One easy way to inspect the secondary side of your ignition(cap, wires, plugs) for a misfire is to wait til it's dark outside, start up the car, get under the hood with a squirt bottle filled with water and spray a mist over the plugs and wires. Look for arcing to ground-they will light up and you should hear an audible 'miss' when spark doesn't make it to the plug. Just a thought.

 

Check that fuel filter.............the gas we get now is crap!
And, don't forget that little media screen in the carb.

 

just a thought here...when you replaced the dist cap did you reset your timing?? maybe too advanced...or?? and recheck firing order on wires

 

Any update on this?

I'm still bettin' on clogged fuel something.

Let us know.