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Discussion Starter #1
Hello,

I think my poor '09 G8 GT has a collapsed DoD lifter (P0306 error, rough idle, smoking off the passenger side tailpipe; problem stayed with #6 cylinder when I moved plug, wire, coil and injector between #4 and #6). No compression test done yet, but next on the list during the PD cycle.

Since I'm probably going head deep into the engine to replace the failed lifter (plus the other three under that head), I thought I'd ask the community for their thoughts on doing a DoD delete / cam on a stock car with 285,000KM Canadian....eh!
(178,000 mile).
The cheap fix is to put in four new DoD lifters into the one head, but I do want to try to keep this car running as long as I can, so the idea of not having the chance of another collapsed lifter / weekend repair has some appeal.

Knowing the block (and everything in it) is getting up there in usage, I don't have plans to drastically change HP if I did remove DoD, so please keep that in mind if you are providing input.


Also, under this request, if someone in the Toronto ? Durham Region area knows where to get the DoD programmed out of the car, I'd appreciate the info, as it will help me sort out how viable to delete would be.

Thanks everyone!
 

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Champion Motorsports in Scarborough are LS engine specialists up here in the sticks.
Give them a call.
 

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Remember, when you do a DOD Delete, you are replacing nearly the entire valve-train. THE entire if you replace the valves. All moving parts, and all valve seals. You will also be wanting to replace cam bearings with the new camshaft since it is likely they'll be worn.

The #2 bearing will probably be grooved by this time given the way the DOD cam is designed. It retains the VVT oil channel in the #2 cam journal for cost savings. You just grind one cam and use it whether the motor has VVT or not. So that will mean a bearing replacement (motor out). Anybody that puts a new cam onto that should be taken out back and sh.... er... scolded firmly. Your typical aftermarket non VVT cam is NOT going to have that channel ground into it.

At this point, I would say the valve train damage precludes your ability to do a compression test safely (at least my cautious standards say so). The cylinder walls would need to tell that story. If they're clean and the crosshatch is there, they are fine. If multiple cylinders had serious scratches, it would mean they need work.

So, I suspect you will be fine. A small cam with some matching springs will do the trick. You don't have to replace valves unless they're worn, and you'll see that in the guides and stems. These 821 (L92) heads are very good heads. At 152K I needed no machining when I did mine these past few months.

So in summary, I would not be averse to a rebuild and upgrade. It just depends on that abuse the motor has taken, how well it was maintained, and thus how much is left in the bottom end. It's a pretty sturdy motor...
 

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Discussion Starter #6
Thanks for this info. While I do self maintain the car, this repair will be deeper into the car than I usually go. Details like those you've brought up would not cross my mind, which is why I solicited input.
 

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Having somebody else do it would indeed allow you to rest easy. :)
 

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Discussion Starter #9
So my baby is apart in the garage as I apply my grade 11/12 mechanics courses to the fun of tearing down the top side of my L76.

After I got the heads off, found the intake lifter on cylinder #6 has physical wear on the roller (no longer round...) vs. being collapsed. Sort of expected some wear (based on collapsed lifter no riding smoothly, but perhaps not to the extent I found. Needless to say, a new cam was needed.

Did not go DOD delete, as I wasn't ready to pull cam bearings out, per notes above. However, as I starting putting things back together this weekend, I found what might have been the cause of the lifter getting worn. When I put the new lifter into the lifter guide, I noticed the replacement one in the problem location rotated in the guide, instead of being locking into one position. Whether this wore out due to unusual forces on it after something else going wrong with the lifter, or it was the root cause, I won't know. However, I'm glad I caught the issue, since I'd hate to have an $11 part make me go through all this work again.
 

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Interesting find. That is curious as the trays are designed to prevent the lifters from turning. Wearing like that would mean the guides are busted. Perhaps somebody used the wrong guide when replacing them in the past?

You know, there is a plus to not doing a DOD delete with a more aggressive cam on a high mileage engine right away. You always have to count on a problem or two surfacing due to the upgrades. I anticipated some of it with mine. Low and behold, I've got an injector ticking in a most strange way. (It's not a lifter). It also didn't make the noise before the tune, so I have posited that it is due to the increased duty cycle on old injectors. The problem was really brought out by a non-tune related and obviously preexisting issue.

In fact, it didn't get to be this bad until today. The - soon to be replaced - MAF sensor is under-reporting airflow as diagnosed by the reported grams/sec of mass air flow being decidedly low in various throttle positions when compared to previous logs. Trims are much leaner, and now the injector in question is really b****ing and crying about it. :cursin::cry: <-- If they had faces this is what they'd look like...

So, yeah... a higher mileage engine may have a part or two that'll start chirping soon after you get done with the fun phase of driving it post-mod... There might also be other sensor related issues that really rear their ugly heads after the tune because it requires further refinement. :D

The life of a gear-head.... Certainly, I hope you are having fun. :D
 

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Interesting find. That is curious as the trays are designed to prevent the lifters from turning. Wearing like that would mean the guides are busted. Perhaps somebody used the wrong guide when replacing them in the past?

You know, there is a plus to not doing a DOD delete with a more aggressive cam on a high mileage engine right away. You always have to count on a problem or two surfacing due to the upgrades. I anticipated some of it with mine. Low and behold, I've got an injector ticking in a most strange way. (It's not a lifter). It also didn't make the noise before the tune, so I have posited that it is due to the increased duty cycle on old injectors. The problem was really brought out by a non-tune related and obviously preexisting issue.

In fact, it didn't get to be this bad until today. The - soon to be replaced - MAF sensor is under-reporting airflow as diagnosed by the reported grams/sec of mass air flow being decidedly low in various throttle positions when compared to previous logs. Trims are much leaner, and now the injector in question is really b****ing and crying about it. :cursin::cry: <-- If they had faces this is what they'd look like...

So, yeah... a higher mileage engine may have a part or two that'll start chirping soon after you get done with the fun phase of driving it post-mod... There might also be other sensor related issues that really rear their ugly heads after the tune because it requires further refinement. :D

The life of a gear-head.... Certainly, I hope you are having fun. :D
What are your injector duty cycles looking like?
 

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I'll PM to continue...
 

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Discussion Starter #13
I'd like to thank everyone that posts information on this board (including links to other LS pages). Your previous experiences with the L76 and the hints and tips that come from have allowed me to return my GT to normal operation. An extra shout out to the members that replied to my post; their input was useful in guiding my repair choices.

Toronto in November is definitely not 'shade tree mechanic' territory, but I have my first 750km on the engine after finishing my rebuild on Saturday night at 11pm. Since I was digging in deeper than I've ever gone on an engine, for me this is a win. New factory cam and new lifters (both AFM and standard), new timing chain and sprockets. No engine codes and it idles smoothly.

Once I get a few more break in kms on it, I'll be willing to really test my work and open it up a bit more on the highway. Until then, I do keep a finger crossed that my mediocre mechanic skills, the GM service manual and this forum have come together to generate a successful long term repair.
 
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csbrown
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