Last time I told you about my displacement-on-demand (DOD) engine and how I killed three lifters. And how my LS/BMW engine swap project sat for two months while I figured out what happened. So, now it’s time to tell you how I fixed the problem.
When one cylinder went dead I followed the usual diagnostic procedures. Find the dead cylinder. Number 1 cylinder. Does that cylinder have spark? Yes. Does it have fuel? Yes. Does it have compression? No. Hmmmm. Number 1 cylinder is a DOD cylinder. Maybe the DOD system is malfunctioning. Can we shut off the whole DOD system? Let’s find the solenoid valve wires and unhook them and see what happens. Hmmmm. Can’t find the wires in the harness. Can’t find a connector at the back of the valley cover.
More research.
Turns out some SUV’s have all the DOD mechanism in place but it’s non-functional. No wires. No program in the ECM. Why? The short wheelbase Envoy and Trailblazer didn’t have enough room for the muffler GM thought was necessary to keep owners from noticing when the engine would cycle back and forth between four and eight cylinders.
My engine was taken from a short wheelbase Envoy so the DOD was already be dis-engaged. That’s when I leaned about the special oil pressure regulator and its relationship to the solenoid valves (see previous post).
If I had known all this stuff when I first bought my engine I could have prevented all these problems with one simple step: Install a valley cover from a Gen IV, non-DOD engine. Turns out all Gen IV engine blocks have the special oil ports that go from the valley area down to the lifter bores. Non-DOD valley covers have no oil feed and of course, no solenoid valves. Plus, they simply block off these lifter ports with O-rings.
I found a valley cover from an LS2 Corvette but only after I had already killed the lifters. Since I had to replace lifters on both banks, I pulled the heads and replaced all the lifters with conventional LS lifters. This requires the appropriate lifter guides as well.
If you aren’t familar with LS roller lifters, you may not understand the role of lifter guides. They are a rectangular plastic piece with holes for four lifters or two cylinder’s worth. The bores into which the lifters fit have a shape that keeps the roller on the lifter lined up with the cam lobe. The DOD guides have a unique shape for the DOD lifters to keep you from interchanging with the non-DOD lifters.
By the way, I’ve been told that all LS lifters, (non-DOD versions) are the same. Mine came from a guy who buys warranty engines and sells the good internal parts.
My engine swap project is back on track. Or, I should say, back on the road. It’s running on eight cylinders. All the time. Like a real engine should.
Does that mean you should avoid DOD engines? No. If you follow a few tips.
1. If you can use the donor oil pan and the DOD is active, it doesn’t complicate wiring in an engine swap because it’s pretty much self-contained between the ECM and the engine. And you should pick up a few miles per gallon.
2. If you need to swap oil pans, then I would recommend you also swap the valley cover and forget DOD. The lifters will be fine if they don’t get any extra oil flow.
3. If you want to install an aftermarket cam, then replace the DOD lifters and guides with conventional pieces. Just be sure that the number of teeth on the reluctor match your ECM.
4. If you need to swap oil pans and you really want to keep the DOD feature, you might figure out a way to adapt the DOD oil pressure regulator into the new pan. Not a challenge I want but if you decide to try it, let me know the results.
In summary, I believe the DOD or AFM engines are good candidates for engine swaps for one main reason: Price. The demand is still low. Many engine swappers will be afraid of them, keeping demand low. Supply is going up as more vehicles are wrecked. That means prices will stay low.
I gave $1500 for an all-aluminum, 300 horse, 5.3 with 17,000 miles. Plus $500 for a matching 4L60e transmission. Even after replacing lifters and the valley cover, even after replacing the tall SUV intake with an LS2 intake and water pump, I still have less invested than a Camaro or Corvette version. And those would likely be much higher miles.
So I say, “DOD may have killed my engine swap (temporarily) and I was pi**ed off (also temporarily) but now all is forgiven.”
Next time I’ll give you some ways to identify DOD or AFM engines.
