Kasar Jehangir, 24, and Adil Aftab, 22, reached speeds of 130mph (209kmph) as they were pursued on the M6 near Walsall.
"Clouds of brown dust" billowed from their Audi as it wove across lanes undertaking cars, Birmingham Crown Court heard.
They were each sentenced to three years for possession with intent to supply.
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The southbound carriageway of the M6 between junctions nine at Wednesbury and seven at Great Barr in the West Midlands was closed to recover the drug, Staffordshire Police said.
Officers estimate the pair threw about 1kg (2.2lbs) of the drug out of the car.
They recovered about 34.2 grams which when tested was of 58% purity.
Anthony McKenzie from the Central Motorway Police Group (CMPG) said the incident in the early hours of 18 July last year was "a significant and time consuming operation".
Jehangir pleaded guilty at Birmingham Crown Court on the first day of his trial on 31 October.
His 36-month sentence will run concurrent to an 11-month sentence he is already serving for dangerous driving, a charge he admitted and was dealt with in January.
Aftab, from Seacroft Avenue in Yardley, Birmingham pleaded guilty to his charges in July.
Supt Elliot Sharrard-Williams, from Staffordshire Police said: "Our colleagues at CMPG pursued the vehicle and not only safely brought the occupants into custody, but enabled a significant amount of heroin to be recovered.
"These sentences should yet again send a strong message to anyone who thinks it is acceptable to peddle drugs within our county."
Two drug dealers who flung heroin out of their car on to a motorway as they fled from police have been jailed.