TRS Write Up on 2.9 Porting

[PetroleumJunkie412]

Hey, figured this may help over here for those seeking performance out of a Scorpio.

As part of my 2.9 FI build, I had to figure out how to port the heads. This is a post I'm working on that is to be come a tech section info page on porting 2.9 heads.

I wound cutting up a cracked 2.9 head and taking silicone molds of the ports. Lots of photos to gander at if you've ever wanted to see port shapes and coolant passages.

Will update with tech section link when finished. Feel free to reuse and post my work as long as author and photo credit is retained.

Thanks all!

https://www.therangerstation.com/forums ... ng.187007/

[brokencase]

I don't think you will get much unless you fit larger valves. A while back there was a guy selling over sized valves on ebay. He has some flow bench numbers that were interesting.

None the less if I were doing an engine rebuild I would do a "cleanup" on the intake ports and focus on the valve area. 3 angle valve job, round the sharp edges on the intake valve itself. I wouldn't touch the exhaust.

Keep in mind it's a "high swirl" design for fuel economy. It relies on high velocity through the ports.

[DPDISXR4Ti]

https://www.therangerstation.com/forums ... ng.187007/

Nice work - thanks for posting!

[PetroleumJunkie412]

I don't think you will get much unless you fit larger valves. A while back there was a guy selling over sized valves on ebay. He has some flow bench numbers that were interesting.

None the less if I were doing an engine rebuild I would do a "cleanup" on the intake ports and focus on the valve area. 3 angle valve job, round the sharp edges on the intake valve itself. I wouldn't touch the exhaust.

Keep in mind it's a "high swirl" design for fuel economy. It relies on high velocity through the ports.

Running same valves, just sourced from different supplier.

Pics of valves, plus build parts list and prices added.

[john keefe]

Great info!

Looks like one of the older 2.9 heads which you cut up. Have you compared to one of the newer aftermarket heads which improved the weak (thin) areas to reduce cracking? (see Brad's thread, viewtopic.php?f=29&t=33657). Wondering if the port profiles around the valves, and the port floors are improved as well? Those are some sharp corners.

As brokencase pointed out, its high-swirl for velocity in an NA application, and you're probably better off focusing on the valves, and mild port cleanup. 90 deg. port angles (down-turn into the cylinder) aren't so good in a NA design, though it does save space/height. Works fine in a boosted situation, like the Cosworth YB (Sierra) when the bowl is ultra clean, no sharp corners, and no/minimal valve boss exposed. The boosted pressure and fabricated velocity overcomes the sharp turn, and makes for a shorter, compact OHC architecture.

In comparison, even a lowly stock 5.0L head has port angles along the lines of 35-40 deg, with Hi-Po heads (Yates, WP, AFR, etc.) either angling the port steeper, and/or opening up the stock path to a straighter configuration.

The 2.9L's 90deg. port channel near/around the valve(s) is necked-down to create velocity, maybe even some intentional turbulence to better mix the downstream injected fuel. Basic Bernouli's, if you hog out the port roof, as a couple of the illustrations show, you're increasing flow pressure at the expense of lower velocity. But, that increased pressure in a NA application won't be as beneficial as flow velocity in the milliseconds it takes the piston to complete the intake stroke. Especially for a 90deg. NA port.

Typical complaint when guys port their 5.0L heads, and end up losing performance (or when guys hog out the XR's intakes too much). The vacuum side of the equation (piston downstroke) isn't enough to take advantage of the higher pressure gradient, unless you do other things like larger valves, a cam regrind with higher lift/duration, etc., and in the case of the XR, increasing boost. And, to follow, higher flow injectors for the increased air mass, etc., etc.

The "mild" port cleanups in the other illustrations would be good, especially around the valve bosses, but I'd be wary off clipping the curve at the floor just above the valve... those all look like water passages for cooling, and that mass of iron is probably crucial for heat dissipation. Just MHO.

[brokencase]

This is what I mean by focusing on the valve shape and 3 angle valve job....left is stock and right is after the modifications.
You end up with a thinner valve seat (but you can't go too thin!). These changes to the valve and the seat greatly improve flow at low valve lifts. Helps to have a metal lathe to shape the valves and the valve seat cutters.

valvework.jpg (26.22 KiB) Viewed 3026 times

[Bob Weir]

This an interesting thread for "Jon V", considering he's built performance 2.9s.