SA_swaps

Working on a 08 5.3 LC9, does not have vvt only dod/afm. The dod had issues so decided to delete it. Installed 16 new lifters, new oil pump, ls3 valley cover. Disabled Dod in the tune and dtcs. The engine runs really bad at idle. Texas speed assures me every time I talk to them the stock camshaft will work. They do them all the time with the stock cam. Thunder Racing disagrees they say it will NOT work. The cylinders that had dod have 100psi compression and the ones that did not have 150 psi. In theory the factory cam should work, people delete it thru the tune and basically it should be the same as what we installed. I dont get stumped often but this has got me. I have spent hours searching forums and still have not come to a conclusion.

Anyone have any experience at this that can help me to figure out what is wrong? I no the cam has diffident lobes on the dod cylinders 1.3mm difference i believe.
Thanks,

85MikeTPI

iTrader: (9)

I wouldn't for the mere fact that the lobes are different.. Did you measure and get new pushrods?

SA_swaps

The pushrods seem to have the same preload as the non dod cylinders at top dead center of the cylinder.

bigbadblack93z

iTrader: (8)

need to find out the root of the compression psi difference. is it hanging the valves open(should be if adjusted properly) its possible that the rings are toast from the oil consumption issues those motors have. spray some oil in there and test it again, if the numbers come up its rings.

SA_swaps

It didn't come in the shop running this bad, but I will try it.

SA_swaps

Installed a stock non dod 5.3 camshaft, compression is equal on all cylinders and engine runs like it is suppose to. Called tsp to let them know for future reference, basically said I was wrong it didn't fix it I had to have changed something else.

litle88

iTrader: (20)

Oh wow!

Sales2@Texas-speed

iTrader: (5)

Step back and think about how the camshaft is ground, and how the lifters ride, and why/how the valves open. If you know how they grind the AFM cams, you know the lobes are still in the same location as a non-AFM camshaft, they just use different lobes (and sometimes different centerlines).

So do tell us all why the cam makes any difference. I found 2 local truck guys here that did the same DOD delete kit, are running the stock cam, and have no problems.

SteveDoten@ARH

I had a 2006 5.3 DoD motor I was working on a few weeks ago in a Envoy/Denali; Replaced all lifters; motor had a dead cyl. on #6

Fixed the problem replacing the lifters, those DoD lifters are about $45 each/the lifter trays are $18

What did you use for lifter trays? the DoD motors use an offset notch on the 'center' block side while the LS2(non DoD '05up LS) use the notch towards the front/back of the block..........not that this matters if using LS2 trays with the standard LS lifter

bww3588

iTrader: (49)

This is interesting...

SA_swaps

Yeap Yeap very interesting. Time will tell the story.

Inspector12

iTrader: (29)

Well I will tell you guys that say it works just replacing the lifters and using the stock DOD cam, that is not the case with ALL the trucks. I can't call BS on everyone elses trucks. But I can tell you that I am VERY experienced to say the least if anyone knows me or has followed any of my builds would know. And the truck I was working on would missfire on the DOD cylinders at idle. Ran fine while driving, but seemed a little down on TQ but over all ran decent. Worked with a friend at the dealership to try and figure out what is going on. Finally I came to the conclusion that the cam's are different in some way. I believe it to be Lift to try and keep those cylinders quiet when the DOD is active. But with out cam doctoring the cam I can't say for sure. I stuck a stock cam in the truck and it fixed EVERYTHING! I didn't change ANYTHING in the tune etc... Just the cam. Just a little FYI for someone searching for a simular issue with there truck etc... GL! And just so you know that a cam can be ground with the lobes being different on every cylinder. It's done on intentionally on big block chevy's because the cam core's are so small that the high presure valve springs/valvetrain cause the cam's to twist under extreme RPM's etc... So they grind the cam's with different lobes at differnt timing to compensate for this little problem.

nmp0098

The DOD lifters are not as stiff as the non-DOD lifters, so even if you wanted identical valve lift you would have to run different (larger) lobes with DOD lifters. I had my DOD cam measured a while back and the difference in lobes was stark, especially the "advertised" duration. The duration gets closer for higher lobe lift. The difference in cylinder compression you measured was due to all of that extra low lift duration. It smooths out at higher RPM when that part of the lobe doesn't matter as much.

redriver racing

The cams r different. I done a dod delete in a 2009 5.3 and it done the same thing urs was doing at idle. Changed cams everything was fine. Now when we do one the cam gets changed. Have done several now and have not had anymore problems.

busta9876

iTrader: (3)

Thanks to this thread, saved a lot of head ache on a 07 Silverado. at 160xxx miles lifter come apart, bent push rod, installed two new AFM lifters, put head back on, and within one month, one of the NEW AFM lifters stuck in the de-activated position. This time installed 16 new LS7 lifters, changed guides and valley plate, and what do you know, we had misfire at idle on all AFM cylinders. Otherwise ran great. At this point we found this thread. Installed a used 2003 5.3L camshaft and changed to a 3 bolt sprocket (4x) and now the truck runs great.

After installing new lifters, BEFORE installing 03 camshaft, AFM cylinder compression was 125 after 3 strokes. The NON-AFM cylinders compression was 150-155.

SA_swaps

Glad I could be some help. Still no word from Matt guess he is still stepping back and thinking about how that cam works . I found more than 2 guys that said it will NOT work. hmmmm I guess we all left that same ground wire off.

LS6

It got useful infomation on the engine isuue when DOD is deleted

busta9876

iTrader: (3)

I'm sending a factory 2007 AFM camshaft off to Bullet to have them put it on a cam doctor. Talking with a guy there, he would imagine the cam to have different lobe profiles with less aggressive ramp rates, possibly lash ramps like solid cams have. Will reply when I get more info.

SA_swaps

I can't wait to hear what it is.

Clare-Branden Jones

Busta9876, did you ever get any word back on this?

I posted a month or so ago about a 06 5.3 trailblazer I was working on. Had failed #7 Lifter. It wasnt my decision, but we only changed out the 2 lifters on that cyl. I explained that was either an isolated bad lifter or a design flaw and could see it again on other lifters. 3k miles later its back with #6 lifter failure.

So at this point, I am recomending DOD/AFM delete. All new non DOD/AFM lifters, cam, and even oil pump. I had read from GM that a different oil pump was used on DOD/AFM engines. I am thinking that this is the cause for the failure. Loss of oil pressure not pumping the lifters back up.

I own a 2006 Impala SS, with the same AFM/DOD 5.3 I only have 80k miles and have yet to see it drop a lifter but have had the oil consumption issue. The undated oil pan gasket was changed, this had a tab to some how help, "eventhough I dont understand how". But it has not helped. This car has recently started to have erratic 4 to 8 while cruising at highway speeds. From What I have read this is also a known issue with these engines cracking plugs, Causing pressure loss in cyl and tripping solenoid?

This is such a bad design from GM... I am at a loss. Sorry to Hijack thread..