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Old 06-29-2008, 09:37 PM   #1
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Default 5.3 LH6 Progress and Problems

Greetings from the Geezer,

Well, I've been busy. After a year and a half, I got the BMW 535iS on the road with what I call my Baby LS2. The engine is an all aluminum 5.3 out of a 2005 GMC Envoy with an LS2 intake, water pump and crank pulley.

I even joined the Hot Rod Power Tour for a couple of stops.

As is usual for projects like this, there was a major last minute thrash complicated by one cylinder that decided to die about two weeks before the Power Tour. Problem turned out to be a collapsed lifter--one of the Displacement On Demand (DOD) lifters. Well, I found out that I can pull the driver's side cylinder head without removing the engine and I have skinned knuckles to prove it.

The engine still didn't feel quite right but it ran well enough for a couple of speed bursts over 100 with some of the Power Tour boys out in the Kansas prairie south of Topeka. I thought maybe the roughness was a mis-match between my 5.3 ECM and the larger LS2 injectors.

Then I got an email from another LS fan who mentioned that the DOD oil pan has an extra oil pressure regulator and he asked if the GTO pan that I swapped in had that regulator. The answer is no but I wasn't sure whether that mattered.

Some time spent with the Helms shop manual shows how the DOD lifters get extra oil flow through a special manifold to disengage those cylinders. It appears that the solenoids which open these passageways allow a small oil flow all the time and then allow a whole bunch of flow when it's time to shut those cylinders off.

One of the surprises when I was trying to figure why one cylinder was dead was that my particular 5.3 has all the DOD mechanisms (lifters, solenoids, etc.) but it's not activated--there's no DOD wiring between the ECM and the solenoids!

So here's the latest report--I have one cylinder dead again. I haven't had time to check #1 which was the culprit last time because I have to remove the alternator to get a compression tester in there. But I did check #4 which is one of the other DOD cylinders and easy, well, easier, to check. I installed the tester and started the engine several times. Only one time did I get 125 lbs. When I would release the tester it would take several revolutions to build up to about 75 lbs. typically.

Here's my guess--without the special pressure regulator in place, enough flow and pressure is getting past the solenoids to disengage those lifters at least part of the time and that's what accounts for the low compression and roughness and stumbling beyond the obvious one dead cylinder.

If that's true, then one solution would be to tap and plug those special lifter passages. They show up as 8 pedestals in the lifter valley and are connected to the manifold cast into the valley cover.

I'm at that stage in the project where I sometimes wish I had started with a passenger LS engine instead of the 5.3. But, if the LS community can figure out how to make these DOD engines work, we have a another big pool of light-weight, 300 HP, low mileage and relatively cheap engines to work with.

So, how about it? Anyone else have any experiences to share with DOD?
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Old 06-29-2008, 10:51 PM   #2
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Quote:
Originally Posted by Geezer's Garage View Post
Greetings from the Geezer,

Well, I've been busy. After a year and a half, I got the BMW 535iS on the road with what I call my Baby LS2. The engine is an all aluminum 5.3 out of a 2005 GMC Envoy with an LS2 intake, water pump and crank pulley.

I even joined the Hot Rod Power Tour for a couple of stops.

As is usual for projects like this, there was a major last minute thrash complicated by one cylinder that decided to die about two weeks before the Power Tour. Problem turned out to be a collapsed lifter--one of the Displacement On Demand (DOD) lifters. Well, I found out that I can pull the driver's side cylinder head without removing the engine and I have skinned knuckles to prove it.

The engine still didn't feel quite right but it ran well enough for a couple of speed bursts over 100 with some of the Power Tour boys out in the Kansas prairie south of Topeka. I thought maybe the roughness was a mis-match between my 5.3 ECM and the larger LS2 injectors.

Then I got an email from another LS fan who mentioned that the DOD oil pan has an extra oil pressure regulator and he asked if the GTO pan that I swapped in had that regulator. The answer is no but I wasn't sure whether that mattered.

Some time spent with the Helms shop manual shows how the DOD lifters get extra oil flow through a special manifold to disengage those cylinders. It appears that the solenoids which open these passageways allow a small oil flow all the time and then allow a whole bunch of flow when it's time to shut those cylinders off.

One of the surprises when I was trying to figure why one cylinder was dead was that my particular 5.3 has all the DOD mechanisms (lifters, solenoids, etc.) but it's not activated--there's no DOD wiring between the ECM and the solenoids!

So here's the latest report--I have one cylinder dead again. I haven't had time to check #1 which was the culprit last time because I have to remove the alternator to get a compression tester in there. But I did check #4 which is one of the other DOD cylinders and easy, well, easier, to check. I installed the tester and started the engine several times. Only one time did I get 125 lbs. When I would release the tester it would take several revolutions to build up to about 75 lbs. typically.

Here's my guess--without the special pressure regulator in place, enough flow and pressure is getting past the solenoids to disengage those lifters at least part of the time and that's what accounts for the low compression and roughness and stumbling beyond the obvious one dead cylinder.

If that's true, then one solution would be to tap and plug those special lifter passages. They show up as 8 pedestals in the lifter valley and are connected to the manifold cast into the valley cover.

I'm at that stage in the project where I sometimes wish I had started with a passenger LS engine instead of the 5.3. But, if the LS community can figure out how to make these DOD engines work, we have a another big pool of light-weight, 300 HP, low mileage and relatively cheap engines to work with.

So, how about it? Anyone else have any experiences to share with DOD?
Interesting post Geezer. That's the first hard info I have heard of re the solenoids are permitting a "wetting" amount of oil through even when they aren't open. Guess that keeps the seals healthy and lube'd. And is no doubt why GM installed an extra pressure regulator in the pan to limit oil pressure to around 65psi on average. Too much pressure equals DOD on and the roughness/stumbling you have had. The DOD actuators in the lifters have only light spring pressure to keep them in place for non DOD operation.

The best/easiest answer to sealing the galleries that run through the valley pedestals is a late LS2 plain valley cover. It comes complete with the right seals to shut these galleries closed.

Trust this helps man.
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Old 06-30-2008, 03:32 AM   #3
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Pull the DOD lifters and replace them with traditional units. You are going to need LS7 lifter guides but they are only $5 each from scoggin dickey.

There is some debate as to if plugging the feeds is necessary, but as you said it is fairly straight forward so why no do it. If anything you may gain some oil pressure thanks to the upgraded pump on those motors.

Last edited by NoClassic; 06-30-2008 at 03:49 AM..
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Old 06-30-2008, 09:18 AM   #4
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Replacing the DOD lifters sounds like a good idea, especially since the DOD lifters retail for $70 each. I read some place that the DOD lobes have a different amount of lift. I wonder if that would also require different length pushrods?
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Old 06-30-2008, 09:35 AM   #5
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Thought that there may be some interest in what is inside the DOD DEAC lifters, and potential extra points of failure:

Left hand side shows the main lifter body with the smaller lifter oiling port, and the larger DOD control port.

Above the lifter body is the DOD plunger return spring and retainer, and washer.

On the right hand side is the DOD plunger, showing the activation pistons and preload spring, and above that the pushrod seat, oil metering plate, lifter plunger with lifter check valve and pre load spring.

The activation pistons measure 0.275" in diameter, and require around 1 lb of force to compress to fully flush with the DOD plunger. (around 16 psi?)

When they are fully flush, they dis-engage the DOD DEAC plunger which carries the lifter plunger and pushrod seat, from the main lifter body, allowing the main lifter body to ride up and down on the cam, without transferring any motion to the pushrod.

Oil pressure is applied via the DOD DEAC solenoids in the valley cover, under ECM control, which depresses the activation pistons so they dis-engage from a slot in side the main lifter body.

When the ECM commands re-activation of the 4 DOD cylinders, the oil pressure is released which allows the activation pistons to extend under pressure of the their pre load spring, and be the DOD plunger to be pulled by the return spring back to its normal operating position and for the activation pistons to re-engage and lock into the main lifter body allowing the lifter to operate normally.

5.3 LH6 Progress and Problems-dod-deac-lifter-disassembled.jpg

Based on some enquiries I have had, there are some misconceptions around what DOD/AFM does. DOD allows the valves to stay closed. It disconnects the valve train from the cam. It does not keep the valves open.

This does create some pumping loss, but the energy stored in the "compression" stroke is mostly returned to the system on the "power" stroke. The non DOD cylinders work harder, consume a little more fuel, but they run more efficiently due to higher mean pressure, which is where the fuel saving comes from.

Imagine if the valves were held open? Hot exhaust gas would be backflowing into the cylinders and the intake manifold. Essentially connecting hot exhaust gas to injector fuel spray.

cheers!

Last edited by rsz288; 06-30-2008 at 08:27 PM.. Reason: Clarity added....
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Old 06-30-2008, 09:51 AM   #6
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Quote:
Originally Posted by Geezer's Garage View Post
Replacing the DOD lifters sounds like a good idea, especially since the DOD lifters retail for $70 each. I read some place that the DOD lobes have a different amount of lift. I wonder if that would also require different length pushrods?
There is a additional 0.008-0.010" lift to compensate for compliance in the additional pieces of the lifter. No changes to pusrods required. The additional lift is targetted to have the valves all doing the same dance.
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Old 06-30-2008, 10:36 AM   #7
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Hey man, I really appreciate all the info. Thanks especially for the exploded lifter photo. It's becoming clearer all the time that the GTO oil pan swap also needs an LS2 valley cover to shut off the DOD passages. And, a full lifter swap would also be a good idea when I fix the current dead cylinder.
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Old 06-30-2008, 06:36 PM   #8
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Quote:
Originally Posted by Geezer's Garage View Post
One of the surprises when I was trying to figure why one cylinder was dead was that my particular 5.3 has all the DOD mechanisms (lifters, solenoids, etc.) but it's not activated--there's no DOD wiring between the ECM and the solenoids!
I mentioned this in one of your posts a long time ago. I have the same 2005 LH6 engine in my Jeep.

I wasn't aware of the extra regulator in the pan, interesting. I swapped out my DOD (crap IMO) lifters in favor of LS7's when I upgraded the heads. Only thing I had to do there was switch to the LS2 type lifter guides. Either way, the DOD lifters would have never survived in my engine with the cam I'm running - and it's not even that big of a grind.

Do you know if the regulator in the pan is mechanically or electrically controlled? I haven't noticed any negative impacts with the setup I'm running and have flogged the hell out of the motor out on the trails a LOT lately The only thing I have noticed is that this motor doesn't produce as much oil pressure as all of my other LS motors in the past. Of course, I'm running all autometer gauges and figured it may just be due to the gauge difference too.

I used standard length pushrods when I swapped heads, although I upgraded to TSP hardened sticks.
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Old 06-30-2008, 06:47 PM   #9
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BTW, does anyone see any advantage of me switching to a LS2 valley cover over the current LH6's? Wonder if it would gain me any more pressure..

I'm also contemplating swapping out oil pans as the LH6 type hangs low and not very trail/rock friendly. Plus fellow rock crawlers tease me for the big ol goofy looking hole going through the pan
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Old 06-30-2008, 06:56 PM   #10
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I mentioned this in one of your posts a long time ago. I have the same 2005 LH6 engine in my Jeep.

I wasn't aware of the extra regulator in the pan, interesting. I swapped out my DOD (crap IMO) lifters in favor of LS7's when I upgraded the heads. Only thing I had to do there was switch to the LS2 type lifter guides. Either way, the DOD lifters would have never survived in my engine with the cam I'm running - and it's not even that big of a grind.

Do you know if the regulator in the pan is mechanically or electrically controlled? I haven't noticed any negative impacts with the setup I'm running and have flogged the hell out of the motor out on the trails a LOT lately The only thing I have noticed is that this motor doesn't produce as much oil pressure as all of my other LS motors in the past. Of course, I'm running all autometer gauges and figured it may just be due to the gauge difference too.

I used standard length pushrods when I swapped heads, although I upgraded to TSP hardened sticks.
The reg in the pan is a mechanical device. Spring loaded valve. They seem to be in both DOD and non DOD pans now. Makes sense. Simplifies GM stock.

Cheers.
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Old 06-30-2008, 07:23 PM   #11
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Good info, thanks.
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Old 08-22-2009, 10:48 AM   #12
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Anybody know if the pressure spring int the pan is in GMs new pan being marketed for swaps?
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Old 08-22-2009, 10:48 AM
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