1990 Ford Bronco Sputtering and spitting at 70 mph

1990 FORD BRONCO
100,000 MILES • 5.8L • V8 • 4WD • AUTOMATIC
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BPOULSEN
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I have a 1990 Ford bronco with a 351 Windsor and a holly single pump four barrel carburetor also has an HEI distributor we've changed the fuel pump in a run strong except when it switches into overdrive and hit 70 we have put a new fuel pump on and it still does that at 70 it has a we were wondering may need a Holly double pumper four barrel carb. We have tried everything to no avail please advise
Jul 14, 2015 at 2:04 PM
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HMAC300
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what else has been done to this motor? probably it is running to lean or a vacuum leak so fixing carb to run richer may solve the problem.
Jul 15, 2015 at 7:15 AM
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BPOULSEN
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We put a new HEI distributor with the built in ignition coil, a new electric choke on the carburetor a new condenser to get the AC working we put a new HEI distributor with the built in ignition coil, a new electric choke on the carburetor a new condenser to get the AC working also we bought a shift kit from US shift to run the E4 OD transmission, he did not have any computer to run it the The truck can revel up to 5000 RPM with no issues and it runs fine until we get to 70. Please advise
Jul 15, 2015 at 9:09 AM
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HMAC300
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check vacuum at idle if 15" or below suspect a clogged exhaust. bu tit still sounds like it's running lean.......also check timing on it
Jul 15, 2015 at 9:30 AM