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Old 01-22-2013, 09:39 AM
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76 Chevy C10 w/ 350 uphill surging

Highway driving at 65 and 70 mph, when you start up hill it starts surging and loping along. It will eventually recover when you crest the next hill. This happens with just the weight of the truck and extra engine load from climbing the hill I'm thinking fuel filter or pints and condenser as it has the Rochester 4 barrel. Any other suggestions would be appreciated

Fuel filter at the carb, is there and inline filter along the frame rail?

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Old 01-22-2013, 10:32 AM
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Originally Posted by Kiestler View Post
Highway driving at 65 and 70 mph, when you start up hill it starts surging and loping along. It will eventually recover when you crest the next hill. This happens with just the weight of the truck and extra engine load from climbing the hill I'm thinking fuel filter or pints and condenser as it has the Rochester 4 barrel. Any other suggestions would be appreciated

Fuel filter at the carb, is there and inline filter along the frame rail?
It could be ignition (timing or overall condition if points-type), or it may be fuel related. If the filter condition is suspect or unknown, replace it/them first and retest.

Has the carb been rebuilt or modified? If the power valve spring is too weak, it will be lean under load. Float level too low. If the secondaries are partially deployed when this happens, it could be a restricted secondary well fill orifice(s).

What happens if you add throttle?

Points-type ignitions have been replaced by the HEI for 40-plus years now. Time to bring it into the later 20th century at least. A swap to an HEI is a win/win. Only downside is acquiring one and wiring it w/o using the factory coil wire (need a non resistor, full battery current supply to the HEI). And some intakes interfere w/the larger diameter of the HEI so it won't fit or will require grinding clearance.

If the vacuum advance isn't set to drop timing under the load the engine's seeing as you climb these hills, that will give you too much timing and that can cause those symptoms.

Do you know the timing numbers- initial, total, and how much the vacuum advance is adding? Is the engine rpm when this happens above or below the point where the mechanical timing is "all in"?
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Old 01-25-2013, 10:50 PM
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If you are using a HEI ignition the , mechanical advance maybe stuck or not working propperly, a bad ignition moduel or a bad ignition pick up coil
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Kiestler (01-26-2013)
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Old 01-26-2013, 06:04 AM
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A stock '76 C10 already has HEI from the factory, but the Quadrajet is an older version than the ones used in cars of the same vintage. It sounds like the part throttle transition is not working right, which could be due to a variety of carb problems.

The only stock fuel filter is the one in the Quadrajet inlet, but many of these have been installed wrong or bypassed over the years. Disconnect the fuel line from the filter housing first, and then carefully unscrew the housing and see if it has all the parts (spring, filter, gasket, etc.) to make it work properly. The fuel filter housing threads are easy to get cross threaded, and sometimes folks remove the guts and epoxy it back in place to get rid of leaks. You can also just add an external filter near the carburetor if the carb filter is screwed up.

Bruce
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Kiestler (01-26-2013)
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Old 01-26-2013, 01:06 PM
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It was just a fuel filter issue

Took out the one at the carb, placed inline filter on frame rail. runs fine now. It was just starving for fuel. Many thanks for your time.
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