Hi everybody here, I have few questions regarding my [my wife's] 2016 LT1 3LT Auto.
The car has only done 20,000 miles and collapse an intake lifter on number 7 cylinder [prior to that ,the car drove beautifully, nice and smooth, plenty of power etc etc].

The car is in New Zealand, so even though it is lowish miles and less than 4 years old the GM warranty doesn't apply
So I'm in for a repair job, which I will do myself [I am mechanically very competent, even though the C7 will be a learning curve]

I want to do a DOD / AFM delete so this won't happen again
There are several options for me.

1: Replace the DOD lifters on the LH side and plug in a "Range Disabler" but we only use the car occasionally so it will need unplugging all the time

2: Replace the DOD lifters on the LH side and delete the AFM feature with a HP Tuner mod [The HP tuner is cheaper here in NZ and doesn't run the battery down when not in use]

3 Replace the DOD lifters on the LH side then plug the DOD oil galleries, then delete the AFM feature with a HP Tuner mod

4 Change all the the DOD lifters to LS7 lifters [or all the lifters], plug the DOD oil galleries, then delete the AFM feature with a HP Tuner mod

Now my question relates to the existing camshaft
Every where I've read, says I must change the camshaft......Which doesn't make sense unless I am after a performance gain. [I know about the different profiles etc]
But wouldn't the performance be exactly the same as an unmodified LT1 thats driven in V8 mode?
The car idles in V8 mode, accelerates in V8 mode as is etc etc, the only thing I will be losing is the V4 mode for light throttle cruising [economy]


All I'm wanting is a car that drives as before, but without the paranoia of another lifter collapsing [I will sacrifice some economy for reliability]
During the last 2 years we only drove 2500 miles per year, so a few extra gallons wont send me broke.

I cant see how deleting the DOD would change the performance from being in V8 mode with normal driving. Or swapping lifters being any different to DOD lifters locked out with a Range disabler

Can any mechanical experts enlighten me before I bite the bullet and do the job [ with actual mechanical reasoning ]


PS: I don't consider "It'll drive like S*** , mechanical advice "

 

Bump, so hopefully somebody can answer this

 

You need to change all of the lifters (at least the dod ones on both banks but do them all). Also, the cam lobes are different on where the dod lifters are. You need to change the cam as well. You can plug all of the ports under the valley cover and then tune out the dod.

 

Thanks for the reply.
I am trying to avoid changing the cam. [If I do, it will be a "low performance" for my wife]
I know the cylinders 1 4 6 7 have different lobe profiles [I'm guessing longer duration to soften the ramp angles when in V4 mode]

De-activating the DOD feature seems acceptable with a tuner using DOD lifters and a stock cam , But as soon as you change the lifters the cam must be swapped .....Why?
Does the stock style lifters have a smaller roller?
Or does the DOD lifter bleed off some lift even when in V8 Mode?

There are plenty of users of the stock cam with DOD lifters and a range disabler [so the DOD lifters stay locked into V8 mode and act like a normal hydraulic lifter]
What is the difference between using DOD lifters locked into V8 Mode or using stock style lifters on the same cam.

The stock LT1 goes like a scolded cat to the average driver, I just can't see how swapping lifters on 4 of the cylinders would make it worse

It just doesn't make sense to me [hence a lot of questions]


Any other takers here?

 

You should be asking these guys.

https://www.texas-speed.com/p-5443-t...elete-kit.aspx

 

Hey if your going to replace the cam ,just install all new lifters,and tune the dod out with HP tuners,

 

I suppose you can be the guinea pig and find out but frankly why would you half-*** a job like that. If you're going to spend the money for the job get it done correctly. It is more expensive to replace the cam but not a huge amount more with the engine that far apart already.

 

I do agree with the above ,but my response was on a cost aspect,if your doing the work yourself than yes replace the cam and lifters delete DOD, but if on a budget, lifters only is a little cheaper,

 

I am not doing a half-assed job. I would swap the cam to one that has stock lift and duration in a heart-beat [I'm trying to keep the stock manners to the car]
The car is only doing 1350 rpm at 100 kph [NZ's speed limit], most aftermarket cams are in the 1800 rpm+ range. A torch red C7 vette is a cop magnet in NZ

The problem I've found so far is trying to get a Stock Gen V Lt1 Corvette grind for a direct injection engine.
I don't want to increase the performance, Just Reliability [I hate doing the job twice if it fails again]

All I can find is Aftermarket High Performance grinds.

I have a dedicated Road Racing car for Track use. And the Corvette is my wife's car. [we use it 1-2 x week to cruise to our local beach for lunch etc [approx 20 miles each time]
I don't want to let an inexperienced driver loose in a peaky over cammed car

Please understand, I am in New Zealand, I cant just pop down to the local "Chevy" dealer for parts [hence the motivation towards reliability]

Edit: If anybody knows of a replacement DOD delete cam with stock duration/lift please point me in the right direction.
Otherwise 8 x new DOD lifters and lock them out on the computer might be the alternative. [the same results as using a "Range" disabler]

 

Our friends over at Texas Speed offer a non-AFM L86 camshaft. The specs look very close to OEM LT1. It would be worth making a phone call.

 

You have to change the cam to eliminate the DOD. There are many folks that tried just changing lifters and ran into problems. You can search HPTuners forums to see for yourself.

There are cams out there that will give you a stock sound and performance. You may have to go custom but it can be done.

 

Just a quick update.
Which confirms what everybody has telling me. But I wanted to know WHY!

I just spend a few hours chatting with a friend who owned a cam grinding business [and development work]
He did some development on the Aussie Holden Commodore R8 which has the same engine.

Basically the Valve lift and Duration on DOD Cylinders was near identical to normal cylinders [he mapped this with a degree wheel and dial test indicator]
BUT.............The cam lift and duration is different [lobe shape]
The DOD lifters have larger orifices inside them, so they require slightly more cam lift [off the base circle] to get the same valve lift.
To do this GM also lengthened the Duration or Ramp.[this was to compensate for the slight cushion in the DOD lifters,and to get the same net result at the valve]
GM did this to give the lifter some "lash" similar to a solid lifter. It is during the lash phase [at the base of the lobe] that the lifter can engage / disengage

Installing a normal lifter onto a DOD cam lobe increases duration and lift. But increasing duration increases valve overlap and decreases cylinder pressures.

This is why it can throw a code at idle speeds .
If I change the lifters, I must change the cam. But if I disable the DOD lifters, I can leave the cam as-is

So if you want to know why, this explains it.

He also told me, they can grind the cam on Cylinders 1-4-6-7 to match the rest of the cam [the hardening is deep enough to do this] So I can get my stock spec cam I desire with DOD Delete.

PS: Does anybody know of any Chevrolet Parts dealers [factory GM] that will mail order parts overseas. I prefer a vender here on the forum to show some support.

Cheers Kerry