327 idles fine, missing under load - Team Camaro Tech
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post #1 of 9 (permalink) Old Feb 24th, 11, 12:38 AM Thread Starter
George
 
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327 idles fine, missing under load

I have '67 with a mild 327, TH400 (just rebuilt), HEI distributor, MSD 6AL box, and Rochester Quadrajet. The car starts and idles fine but when I drive it it hestitates from a stop and then sounds and feels like its mis-firing. The spark plugs are relatively new and I did a visual check of the plug wires and they look pretty good. I looked at the the plug areas with the engine running in the dark and saw no sparks and heard no crackles or pops. I havnet yet checked the resitance on each plug wire. Can you guys please give me some other things I can try. Any help is appreciated. Thanks.
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post #2 of 9 (permalink) Old Feb 24th, 11, 02:52 AM
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Jess
 
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Re: 327 idles fine, missing under load

What kind of ignition are you running? Make sure you have a good coil, yes they can go bad. Also check you points. No points, check your rotor button and dist cap. Make sure none of your 12+ wires have rubbed or have a place where that will ground while you are driving. Have you removed any plug wires and maybe crossed them up. Simple things to check first...

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post #3 of 9 (permalink) Old Feb 24th, 11, 03:07 AM
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Re: 327 idles fine, missing under load

You might look at the accelerator pump linkage on the front left corner of the Q-jet. The arm has two holes for the rod to set in. With engine operating temp, try another hole. The further hole out offers more fuel pumped when pedal depressed.

Might try alittle more initila advance or plug HEI vacuum adv to intake or full time vacuum.
You might try removing the MSD box and re-install the HEI module, run on HEI alone and gap plugs to 0.045". Plug wire resistance is usually 8K per foot.

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post #4 of 9 (permalink) Old Feb 27th, 11, 04:32 PM Thread Starter
George
 
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Re: 327 idles fine, missing under load

Thanks guys. Finally got my multimeter on the wires and I think I have a couple of bad wires. Gonna order a new set and see how it goes.
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post #5 of 9 (permalink) Old Feb 28th, 11, 09:26 PM
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darrell
 
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Re: 327 idles fine, missing under load

if that dont fix it --do away with the vacuam to vacuam advance---i run that same set up for a long long time 700hp on bottle anyway --i didnt run the module in the dist in fact i think msd tells you not to--they make a pig tail that goes from pick up straight to msd i think jegs sells it--i made my own other than that make the ventures are not dripping fuel
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post #6 of 9 (permalink) Old Feb 28th, 11, 09:44 PM
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Re: 327 idles fine, missing under load

The vacuum advance is something most people want to keep, especially on a mild street engine. A 700 hp bottle fed monster is a different story.

The hesitation from a stop is most commonly caused by the accelerator pump.
If the plug wires don't take car of it, check yours or swap in another coil. If the coil is getting weak and peak voltage output is low, it may not be able to jump the spark plug gap under the increased load of acceleration.
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post #7 of 9 (permalink) Old Mar 2nd, 11, 02:35 AM Thread Starter
George
 
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Re: 327 idles fine, missing under load

thanks guys, what kind of problems should I look for with the accelerator pump?
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post #8 of 9 (permalink) Old Mar 2nd, 11, 03:53 AM
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Re: 327 idles fine, missing under load

Any movement of the throttle should pump/squirt fuel into the venturis.
A driving test is needed as either too much fuel pumped or too little fuel pumped can cause a hestitation.
You might try another set of plugs, hotter?, as these may be fouled or misfire under load as in firm acceleration.

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post #9 of 9 (permalink) Old Mar 5th, 11, 11:40 PM Thread Starter
George
 
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Re: 327 idles fine, missing under load

Well I replaced the Mallory 8mm wires with a set of MSD 8.5s and that fixed the problem with missing under load. It still has the problem with the hesitation if you stomp on it so my next step is to look at the accelerator pump. Thanks again for the tips
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