The relative impact of temperature on the double overhead cam Ford and pushrod GM V8 engines has been a major focal point across recent weeks.

A dyno study by Supercars showed the Ford was at a disadvantage in hot ambient conditions, resulting in tweaks to its mapping and restrictor ahead of the Symmons Plains and Wanneroo rounds.

Those changes were designed to equalise the performance of the engines across various ambient temperatures measured at the inlet.

However, it also emerged during the process that the GM engine’s manifold features an extra layer of insulation compared to the Ford courtesy of its ‘skull cap’.

The skull cap – effectively a cover over the top of the manifold – is an original equipment part said to have been included by GM for acoustic reasons.

Supercars motorsport boss Tim Edwards confirmed to Speedcafe the category studied its impact at Wanneroo and presented findings to Ford representatives at Hidden Valley on Friday.

“In Perth we ran some thermocouples (sensors) underneath the skull cap, on top of it, and on the Ford. That captured some information rather than just speculating,” Edwards explained.

“We this week dissected all that information and uncovered the fact it does insulate the manifold from the underbody temperatures, so we’ve allowed the Ford guys to insulate theirs.”

The fact the disparity finding was delivered on the Friday of the hottest race event of the year resulted in Ford and its teams scrambling for a solution.

Tickford Racing came forward with a temporary fix involving the addition of heat shielding of the type already used on the firewall of the cars.

It was trialled on Will Davison’s Dick Johnson Racing entry, which was still fitted with a thermocouple from Perth, during Saturday morning qualifying .

Supercars approved the temporary solution ahead of the races based on data from qualifying, with teams able to choose whether they fitted it or not.

Tickford team manager Matt Roberts said both his cars ran the update but whether it actually proved a benefit is unknown.

“We put it forward to the group and said we need to try something, this is about all we’ve got at our disposal, let’s give it a go,” Roberts explained.

“Is it worth something? Who knows. It was always going to be an unknown. We trialled it in the first session [on Saturday] and it seemed OK.

“We haven’t seen any data to suggest it’s night and day better. We thought we saw in Race 1 there was a small benefit, so we did it on the second car.

“But there is still a [straight line performance] deficit there. We’re still screaming about the obvious problem.”

That problem, according to Roberts, was proven by Tickford driver Cam Waters’ inability to tow up to the back of Camaros late in Saturday’s second race despite being on fresher tyres.

“It’s incredibly frustrating,” Waters told Speedcafe following a 10th place finish in the second Saturday race.

“It’s the third year of Gen3, you come to Darwin and you just get gapped down the straight. You can’t tow up on a GM. There would be over a tenth in it here I think.

“And it’s not just here it’s everywhere. It’s just the level of the deficit. I’m getting really tired of it. The fact it hasn’t been fixed simply isn’t good enough.”

Waters said the problem is worse in race conditions than qualifying, echoing recent comments from Erebus Camaro turned Dick Johnson Racing Mustang driver Brodie Kostecki.

The two Saturday qualifying sessions at Hidden Valley saw wildly different results, with eight Fords in the top 10 for Race 1 and just three for Race 2.

Both races ended with five Fords inside the top 10, albeit with the Triple Eight Camaro of Broc Feeney a dominant force out front.

“Quali is not as bad but as soon as you get in the pack we just really struggle. That probably tells you the story of why, or an area to look for improvement,” said Waters.

“Brodie’s won on the other side and he’s really struggling at the moment and his engine comments are echoing every other Ford driver.

“I really hope something can happen to address it and quickly otherwise it’s just going to be pretty grim.”

Ford will now need to homologate a permanent solution for its manifold insulation, which is the latest example of the Blue Oval playing catch-up to match the Chev.

While taking the skull cap off the Chev engine would seem an obvious solution, Edwards said it’s not that simple.

“It’s an OE (Original Equipment) part,” he said.

“It’s not something [GM Supercars engine builder] Kenny [McNamara] has dreamed up, it’s part of the design. The fuel rail navigates through it.”

As for any claims the Fords still have a temperature issue following the latest fix, Edwards said: “I see no evidence of that. If they’ve got some evidence maybe they’d like to present it to us.”