Making fours and sixes: Engine plans and plants by David Zatz on

As Fiat Chrysler’s new four-cylinder engines are hitting dealer lots, the company is reportedly working on a brand new straight-six engine to go along with it.

The original plan was to use boosted versions of the Pentastar V6, but either size or power constraints made that less practical than a smooth, compact straight-six based on the new “GME” four-cylinders. A reliable source told us that the company may not even have to change some of the production equipment.

Two reliable sources have told us they believe FCA will make the new six-cylinder engines at one of the twin Dundee, Michigan plants and at the Trenton, Michigan complex — one fast line and one slow line. Trenton seems to be FCA’s “go-to” source for engines, with high production and good quality in the past; while Dundee, which has so far made four-cylinder WGE and FIRE engines, is relatively close to the Toledo, Ohio Wrangler plants.

One rumor claims that the Mack I plant, now used for Pentastar V6 engines and parts, will be idled eventually (the Mack II plant is, and will stay, closed), though we have not been able to confirm this. It makes sense that as the inline six goes into high gear, the Pentastar would require less production space, assuming slowly growing sales.

Evidence for the new six-cylinder has been piling up for some time, with the current belief pegging it at around 2.99 liters for lower taxes in certain European countries. Ferrari is likely working on a different engine from the same core architecture for Maserati.

We have not been able to confirm the “Jefferson expanding into Mack Avenue” rumor, but it seems less likely now that Mack will make engines and ship them via a long, long conveyor into Jefferson Avenue, no matter how enjoyable that would be to watch.

Had trade negotiations with Mexico fallen through, Mack II or the empty Dundee plant might have taken the Hemi from Saltillo, Mexico; but the recent trade agreement with Mexico makes that unnecessary for the next 16 years, which is likely to be longer than the current Hemi’s lifespan.