DOD Delete Theory

[The_White_Car]

So I thought about trying to determine the overall length from the DOD roller to the tip of the pushrod, then buying custom length pushrods to match that distance with the non DOD lifters, then using those custom length pushrods on just the DOD cylinders with the new non DOD lifters.

Post #10 and #12 at the forum below make sense to me.

5.3 DOD delete using stock cam?? - LS1TECH - Camaro and Firebird Forum Discussion

Generation IV Internal Engine - 5.3 DOD delete using stock cam?? - Had a 5.3 go down (bad lifter and dropped valve into cylinder) Got a replacement engine on the way. Im going to suggest deleting the DOD lifters but I know they wont go for a cam swap. This is purely for reliability. My question...

ls1tech.com

However, I do not believe that 15PSI less will cause an issue but I would not risk it for my own sanity. You, however, say you don't mind tearing back into the engine again so I say go for it. I would love to have the data. Get compression tests on all 8 cylinders after the fact and let us know if you get any check engine lights.

I actually have the dumb thought to just replace all lifters with new versions of themselves. I figure if they went 200k the first time before causing issues what's the harm in running the exact same ones for the next 200k?

 

[RET423]

I think the loss of compression is a lot more than 15 psi on the DOD cylinders if you just swap out the lifters, I was hearing 55 to 60 psi cranking compression from a couple guys who tried it but I wasn't there so I can't verify that; but I doubt 15 psi below normal would register a misfire.

I am looking for normal V8 performance with balanced cylinders, if it comes up different than that I will change out the cam.

 

[RET423]

That link from LS1tech is one of the threads I read when I got this idea, lots of guys have tried using the DOD cam but I haven't read of anyone trying to use the DOD cam and correct the geometry with pushrod length; I am going to be the Guinea Pig I suppose

 

[RET423]

So, did you confirm that the oem pushrods are different lengths yet? What is the length of the dod pushrods? What is the length of the non-dod pushrods?

The factory setup is all 16 pushrods are the same 7.397 inches according to GM.

 

[Donal]

The factory setup is all 16 pushrods are the same 7.397 inches according to GM.

OMG finally. Please post it again! All pushrods are the same length! All pushrods are the same length!

I disassembled several of the dod lifters yesterday and will try to get photographs loaded into the computer. Probably not many posters are interested in seeing how the lifters can function.

 

[RET423]

OMG finally. Please post it again! All pushrods are the same length! All pushrods are the same length!

I disassembled several of the dod lifters yesterday and will try to get photographs loaded into the computer. Probably not many posters are interested in seeing how the lifters can function.

There is a couple good YouTube videos that disassemble the DOD lifters and show what happens when they fail to reseat in the V8 mode, interesting theory but also becomes obvious why they are such a trouble spot

 

[Donal]

There is a couple good YouTube videos that disassemble the DOD lifters and show what happens when they fail to reseat in the V8 mode, interesting theory but also becomes obvious why they are such a trouble spot

Thank you for exploding some of the myths of the DOD valve train. I hope that you keep going and do the same for the camshaft.

 

[TJBrown]

That link from LS1tech is one of the threads I read when I got this idea, lots of guys have tried using the DOD cam but I haven't read of anyone trying to use the DOD cam and correct the geometry with pushrod length; I am going to be the Guinea Pig I suppose

 

[TJBrown]

I have been following the DOD thing for some time. Being an aircraft mechanic for over 50 years, would love to see the outcome of this. Please share your findings !!!

 

[RET423]

I have a partial update, didn't get as much time on the engine as I wanted this weekend but I did get the heads off & lifters out.

It was what I was expecting, the only lifter that was stuck was the #1 intake DOD lifter, all 16 lifters had no damage on any of the rollers and the cam lobes all look great so this engine is a good candidate for this experiment.

I had 4 busted exhaust manifold bolts to deal with and a bad stud on the exhaust manifold bell to deal with (on the tight Envoy engine compartment the exhaust manifolds must be removed to get to the lower head bolts).

All but the gasket cleanup is done so I am hoping to get the heads back on tomorrow so I can measure for the pushrods, if I do I will post the difference between the DOD cylinder pushrod lengths and the non DOD (if any) and get the pushrods ordered; if there is no difference in the length then that means my theory is a dud.

Hopefully I will know by tomorrow evening