Chevy Truck 250 update

Courtland1949 · Nov 16, 2019

I've got the Chevy truck -250 cu dialed in with a timing light, carb adjustment & idle(I found the pickup for the tach

) The truck runs out nice until you reach 45 mph, and then it wants to faulter and lay down. Losing power. Is the issue with the centrifugal weights not opening enough or vacuum? Vac at carb was meas at 21...

RogerinIowa · Nov 16, 2019

Fuel filter or pump?

centash · Nov 16, 2019

X2

Ben

Janicholson · Nov 16, 2019

Likely (as noted) the fuel supply. Jim

Steve@Advance · Nov 16, 2019

Could be points out of adjustment or worn distributor bushings (if point type).

There is a filter inside the fuel inlet of the carb.

The fuel pump may be weak, the rubber lines at the pump and at the tank may be cracked and sucking air. The old pumps and hoses don't like ethanol fuel or sitting unused.

rustred · Nov 17, 2019

You could do a flow check on the fuel pump and check the pressure. Should full flow out of line a couple feet with engine cranking. Use care.

Courtland1949 · Nov 17, 2019

I just installed a new fuel filter. Why? Because this is a new to me 1976 PU.

Jo Bird · Nov 17, 2019

Did you pull the vacuum line off the carb and plug it before setting the base timing ?

Papaw8 · Nov 17, 2019

As said below most likely fuel starvation. Set timing with vacuum advance line plugged.speed engine up and watch timing marks with timing light to check centrifugal advance. With engine speeded up plug vacuum line on and mark should advance further if vacuum advance is working. Vacuum advance will not cause it to loose power only works at light load for increased mileage.centrifugal advance will affect power. May have an egr valve test with hose plugged. Also power valve in carb could be stuck or restricted exhaust. Most likely starving for fuel.

JerryCPP(WA) · Nov 17, 2019

In another life I sold auto parts for 20+ years. In the '60's and '70's it was painfully common for a guy to come in and insist on buying a new fuel pump and/or carburetor, and we'd suggest a new coil. We'd had Eclin factory reps tell us many times those GM coils often didn't do the job under load. We sold a "Hi Performance" gold-plated coil - it's amazing how many fuel problems those coils solved.

Bob · Nov 17, 2019

(quoted from post at 22:00:29 11/16/19) I've got the Chevy truck -250 cu dialed in with a timing light, carb adjustment & idle(I found the pickup for the tach ) The truck runs out nice until you reach 45 mph, and then it wants to faulter and lay down. Losing power. Is the issue with the centrifugal weights not opening enough or vacuum? Vac at carb was meas at 21...

If you have access to a decent fuel pressure gauge kit with adapter fittings you can "T" into the fuel line without cutting any lines.

Connect it up and monitor fuel pressure when it's running well, and watch what happens to the pressure when it begins to mess up.

Courtland1949 · Nov 17, 2019

Fuel filter was in backwards. Oops.

CenTex Farmall · Nov 17, 2019

Carb float level?

Hobo,NC · Nov 17, 2019

To answer your question you need to check total timing. I spec every chebby 250 6 I have ever worked on over advance... A shadtree fix is to drop a cotter pin in a slot on the vacuum advance to limit travel of the vacuum advance arm.

If base time is correct you could just do away with the vacuum advance cuzz they do not need a boat load of advance to start off with... Even then you do not know what the mechanical advance is doing...

Balls in your corner whats the total timing...

Chevy Truck 250 update

Courtland1949

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RogerinIowa

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centash

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Janicholson

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Steve@Advance

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rustred

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Courtland1949

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Jo Bird

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Papaw8

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JerryCPP(WA)

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Bob

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Courtland1949

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CenTex Farmall

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Hobo,NC

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