He holds the course record of 54.96s, which he set on his penultimate run last year.
"The record is going to get beaten again, for sure. The weather is looking perfect, so everyone's going to be pushing harder," said Cox.
"I can't wait for the battle. I want one of them to beat the record and then I'm going to beat it again. They're both big international stars – they've come to knock me off the top spot and it will be a great battle. But I'm going there to win."
Cox has raced against McRae on gravel at the 2015 revamped edition of Race to the Sky.
"It was only our second-ever gravel event in that car, so we were still getting to know the car. I've also raced against him all four years at Leadfoot on tarmac, coming second to him the last two years. If we all get to the top four, it's going to be awesome, but these cars are finely-tuned so let's hope they will all be reliable for an epic battle."
There is a lot riding on Cox's abilities as a mechanic as well as a driver, because he does the bulk of the work on the car himself.
Currently weighing about 1000kg and putting out just more than 500kW at the wheels, the space frame and aluminium shell Hillclimb Special Evo 8 was originally built for Race to the Sky and similar events where there are no regulations on vehicle power or weight.
Running in the open 4WD class, Cox said: "This year we haven't played around with the power too much – our tuning specialist Dave from Dtech is coming with us to help fine tune power to the hill. We know it's about getting the power right through the gears."
The Ashley Forest is located north of Rangiora in North Canterbury.
The event sees all entrants do up to four qualifying runs, time permitting, on Saturday, and one qualifying run on Sunday morning before the elimination runs for top 32 start.
These narrow down into runs for the top 16, eight, four and then the final two fastest competitors.
A cash bonus of $1000 is also awarded to the competitor, if any, who holds the new course record by the end of the weekend.
The Ashley Forest Rallysprint trophy will be presented to the overall winner, and the Ashley Forest 2WD trophy will be awarded to the fastest 2WD competitor.
The Ashley Forest Rallysprint
Event background
Christchurch-based MotorSport New Zealand-affiliated car club Ratec Motorsport Inc has been running the Ashley Forest Rallysprint since 1979. The iconic event is staged over a 1.7km (55 per cent uphill) course in the Ashley Forest, North Canterbury.
The late Kim Austin was a regular in breaking the one minute barrier and his 1999 winning run of 56.57s in a 4WD Mitsubishi Starion V8 remained the course record until 2016 when Cox broke it three times over the weekend. Cox's new course record of 55.23s stood for a year when in 2017 he set a new record of 54.96s.
Also falling in 2017 was Austin's 1988 2WD record of 1m 2.45s by the narrowest of margins to Chris Hey in his Toyota MR2.
