Supercars has explained the engine package tweak awaiting a number of Holden teams in 2021.
The Supercars Commission approved an increase in the rocker ratio from 1.60 to 1.65 in KRE Race Engines-built V8s.
12 of the 24-car Repco Supercars Championship grid runs KRE engines.
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The exact implementation date is still to be determined as parts need to be available for all teams running KRE engines at the same time.
KRE engines are used by Red Bull Ampol Racing, Team 18, Brad Jones Racing, Team Sydney and Matt Stone Racing.
The two remaining Holden teams, Walkinshaw Andretti United and Erebus Motorsport, run Walkinshaw Racing GM engines.
Supercars stated the tweaks will bring the KRE engines in line with the Ford units, and there will be no change to the maximum power limit.
"The 1.65 rocker that was made available to the Ford engine builders has also been made available to the GM engine builders,” a Supercars spokesperson said.
"All engines must still comply with the maximum aggregate engine power, irrespective of which rocker is applied.”
The field will return to Symmons Plains for the third round of the 2021 Repco Supercars Championship.
The event will be broadcast live on Foxtel and will be streamed on Kayo with highlights on 7 and 7 Plus.