Todd Kelly says his Nissan Motorsport squad will need to carefully monitor its three remaining new-specification engines after striking trouble with his own unit in practice.

Kelly will have to revert to a spare fitted with the pre-Bathurst incarnation of the VK56DE’s cylinder head after a problem appeared late in Friday’s fourth and final session.

“When I went out for the last run the guys could see a bit of an indication on the data that it was on its way out, and when I pulled up there was water pouring out of the exhaust pipe,” Kelly told Speedcafe.com.

“They all got through Bathurst fine, but we’ll have to keep a close eye on the rest of them for the remainder of the weekend.

“When we’re this close to the limit of how much material we machine out of the heads it’s not ideal but we kind of have to be there (for performance).”

The 2005 Bathurst 1000 winner added that reverting to the previous specification is particularly galling considering how well the Altimas suit the Surfers Paradise layout.

“We went a little bit the wrong way with the car and we know exactly what we need to do with the car to have a good car around here,” he said.

“Unfortunately it’s pretty tough to have to go back to the old spec engine because this one is one of the few of the year where we’re half a chance to get a good one.”

The revised cylinder head design is touted as both a power and an economy advantage over its predecessor.

They latter quality, however, is significantly less important this weekend due to the 185 litre ‘fuel drop’ rule implemented for the final Pirtek Enduro Cup event.

Around 20 litres more than the leading teams Ford and Holden would need to take onboard across their two pitstops under normal circumstances, engineers are expected to lower their starting fuel loads in order to be sure of fulfilling the drop requirement.