Results elsewhere on Saturday put extra pressure on Newcastle to win last night's Premier League match against Reading at Brough Park, and the Diamonds came up trumps with a 50-42 victory as well as collecting the aggregate bonus point.
Starting the match in ninth place, the win hauled the Diamonds up to sixth spot in the table and they must now depend on other results during the week going their way before they know if they will still be in the top eight by next Sunday's cut-off date.
Reading belied their lowly league position and shocked the home crowd by taking a 5-1 in the opening race when guest rider Travis McGowan, who rides for Oxford in the Elite League, romped away to win in the fastest time by a visiting rider this season.
Newcastle's Josef Franc dropped out of heat 1 with engine trouble, switched to his No 2 bike for the rest of the match, and rode magnificently, beating McGowan three times.
And, even though a Newcastle victory was already assured, their duel in the final heat produced fascinating racing as they passed and re-passed with terrific skill and daring.
Franc just got the verdict and won the Spencer Oliver Memorial Trophy as a result.
That early Reading success, plus a 4-2 in the third race after Lubos Tomicek was also forced to drop out with machine problems, gave the visitors an 11-7 lead.
The Diamonds gradually clawed back the deficit and a 4-2 by Kristian Lund and Jamie Robertson in heat 8 put Newcastle in front for the first time, 25-23.
Robertson is riding brilliantly at Byker these days and came up with his third successive double-figure score, crucially winning heat 12 from Reading danger man Andrew Appleton, and then, in the visitors' last throw of the dice, holding off McGowan who was riding off the handicap mark for double points in the penultimate race.
James Grieves (two) and Phil Morris (one) were the other Newcastle heat winners in another thoroughly entertaining all-round performance.
Team manager George English said: "We are obviously delighted to have finished our home league programme undefeated and we can now do no more than hope we have done enough to qualify for the Jack Young Shield."
NEWCASTLE: Josef Franc 12, Jamie Robertson 12, James Grieves 9, Phil Morris 7, Kristian Lund 6, Lubos Tomicek 3, James Birkinshaw 1.
READING: Travis McGowan 19, Andrew Appleton 11, Zdenek Simota 5, Matt Tresarrieu 5, Richard Woolf 2, Chris Johnson 0.
