Jump to content
  • Sign up for FREE! Become a GM-Trucks.com Member Today!

    In 20 seconds you can become part of the worlds largest and oldest community discussing General Motors, Chevrolet and GMC branded pickups, crossovers, and SUVs. From buying research to owner support, join 1.5 MILLION GM Truck Enthusiasts every month who use GM-Trucks.com as a daily part of their ownership experience. 

Sign in to follow this  
Todd1982

L83 (5.3) Cam options to retain AFM

Recommended Posts

Hello

 

What is available out there for 5.3 camshafts that retain the AFM?

 

Thanks 

Share this post


Link to post
Share on other sites

Give the guys at Brian Tooley or Texas Speed a call and let them know what you are looking for. All I've seen are cams designed for AFM deletes, but they can give you a better answer. 

Share this post


Link to post
Share on other sites
7 minutes ago, pewterliftedz said:

None, the lifters cant take a bigger cam.

The lifter is the part that fails (occasionally) but it isn't the root cause of it's own failure. 

Share this post


Link to post
Share on other sites
1 minute ago, Grumpy Bear said:

The lifter is the part that fails (occasionally) but it isn't the root cause of it's own failure. 

Huh?  The lifter collapses under load and thus fails.  Explain to me what the root cause is.

The fact is that the only reason to swap in a cam is for more power, AFM cams have really low lift and don't make power.

Share this post


Link to post
Share on other sites
7 minutes ago, pewterliftedz said:

Huh?  The lifter collapses under load and thus fails.  Explain to me what the root cause is.

The fact is that the only reason to swap in a cam is for more power, AFM cams have really low lift and don't make power.

I believe the AFM lifter is designed to collapse - that's how it keeps the valves closed on that cylinder in V4 mode.

 

The problem is that when it's in V8 mode there is a ledge that the spring pin engages and this ledge gets mushroomed.  Once that happens, the lifter will collapse to go into V4 mode, but now the inner bore drags on the mushroomed ledge.  In this condition, the lifter can no longer extend so that valve will not open in V8 mode.  What's worse is that it also means there is now no preload on the valvetrain for that valve so you get a no follow condition on the cam.  This is the rattle that you hear and can easily progress to lifter bore and cam damage.

 

There is also a misconception that oil is fed to the AFM lifter in order to make it solid for V8 mode operation.  This is the opposite of what's true as the oil pressure being fed to the lifter actually retracts the spring pins and allows the lifter to collapse.

 

So, when someone says they have a "collapsed lifter", what it really means is that their AFM lifter has collapsed and will not extend on it's own like it should during every single combustion event of V4 mode.

Edited by ksiesel
  • Thanks 1

Share this post


Link to post
Share on other sites
46 minutes ago, ksiesel said:

I believe the AFM lifter is designed to collapse - that's how it keeps the valves closed on that cylinder in V4 mode.

 

The problem is that when it's in V8 mode there is a ledge that the spring pin engages and this ledge gets mushroomed.  Once that happens, the lifter will collapse to go into V4 mode, but now the inner bore drags on the mushroomed ledge.  In this condition, the lifter can no longer extend so that valve will not open in V8 mode.  What's worse is that it also means there is now no preload on the valvetrain for that valve so you get a no follow condition on the cam.  This is the rattle that you hear and can easily progress to lifter bore and cam damage.

 

There is also a misconception that oil is fed to the AFM lifter in order to make it solid for V8 mode operation.  This is the opposite of what's true as the oil pressure being fed to the lifter actually retracts the spring pins and allows the lifter to collapse.

 

So, when someone says they have a "collapsed lifter", what it really means is that their AFM lifter has collapsed and will not extend on it's own like it should during every single combustion event of V4 mode.

I understand that the lifter is designed to compress when AFM is activated, but it will not "reactivate", thus why people use the term collapsed.

Edited by pewterliftedz

Share this post


Link to post
Share on other sites
45 minutes ago, pewterliftedz said:

I understand that the lifter is designed to compress when AFM is activated, but it will not "reactivate", thus why people use the term collapsed.

Melling did a video about the lifter problem. They evaluated numerous failed lifters and they suggested that the VLOM and it’s programming was the root cause of the collapsed lifters. 

 

Comp Cams is where I would look if I was going to keep AFM. I’m not sure what your goals are with the cam (power, speed, etc...), but if you’re not dead set on getting a cam, re-gearing your differential will give you the biggest bang for you buck. Depending on your tires and what gears, you will substantially increase how often you are driving in 4 cylinders and your gas mileage may actually improve. 

Edited by 300 Blackout
  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, 300 Blackout said:

Melling did a video about the lifter problem. They evaluated numerous failed lifters and they suggested that the VLOM and it’s programming was the root cause of the collapsed lifters. 

 

Comp Cams is where I would look if I was going to keep AFM. I’m not sure what your goals are with the cam (power, speed, etc...), but if you’re not dead set on getting a cam, re-gearing your differential will give you the biggest bang for you buck. Depending on your tires and what gears, you will substantially increase how often you are driving in 4 cylinders and your gas mileage may actually improve. 

Re-gearing is a instant seat of pants upgrade.  On my 07 5.3 I swapped from 3.73 to 4.56, and it was awesome.  I'm in the middle of collecting parts to gear swap my truck from 3.23 to 3.73 due to my 34" tires.

Edited by pewterliftedz
  • Like 1

Share this post


Link to post
Share on other sites
8 hours ago, pewterliftedz said:

Huh?  The lifter collapses under load and thus fails.  Explain to me what the root cause is.

The fact is that the only reason to swap in a cam is for more power, AFM cams have really low lift and don't make power.

300 Blackout / Melling Performance answered your first sentence.

 

Let's address the bold type above. 

 

The 5.3 on E-85 makes 1.2 hp/cubic inch and does it at 5600 rpm! Almost 1.3 lbs/ft per cube ! That is a BMEP of 193 psi at peak torque. That is the very ragged edge for E-85 fuel. In 1967 the 289 Ford in Shelby tune produced 305 hp but had to be spun 7,200 rpm to make it. It was peaky and required 100 octane fuel. The 5.3 is a race motor that is as meek as a kitten. A very effective camshaft.

 

My guess is you are not very old.  

 

Share this post


Link to post
Share on other sites
300 Blackout / Melling Performance answered your first sentence.
 
Let's address the bold type above. 
 
The 5.3 on E-85 makes 1.2 hp/cubic inch and does it at 5600 rpm! Almost 1.3 lbs/ft per cube ! That is a BMEP of 193 psi at peak torque. That is the very ragged edge for E-85 fuel. In 1967 the 289 Ford in Shelby tune produced 305 hp but had to be spun 7,200 rpm to make it. It was peaky and required 100 octane fuel. The 5.3 is a race motor that is as meek as a kitten. A very effective camshaft.
 
My guess is you are not very old.  
 
This reminds me of the "Why are Chevy trucks so slow?" thread.

They really aren't, for what they are in today's world.

But nobody will be satisfied until their factory built 1500 can match a Corvette.

Sent from my SAMSUNG-SM-J727A using Tapatalk

  • Like 1

Share this post


Link to post
Share on other sites
8 hours ago, Grumpy Bear said:

300 Blackout / Melling Performance answered your first sentence.

 

Let's address the bold type above. 

 

The 5.3 on E-85 makes 1.2 hp/cubic inch and does it at 5600 rpm! Almost 1.3 lbs/ft per cube ! That is a BMEP of 193 psi at peak torque. That is the very ragged edge for E-85 fuel. In 1967 the 289 Ford in Shelby tune produced 305 hp but had to be spun 7,200 rpm to make it. It was peaky and required 100 octane fuel. The 5.3 is a race motor that is as meek as a kitten. A very effective camshaft.

 

My guess is you are not very old.  

 

The AFM 5.3 leaves a lot to be desired compared to a aftermarket cam.  Have you ever driven one of these trucks with a cam, tune, or long tube headers?  These LT1 based engines can have huge gains with these mods, but you won’t get the huge gains with AFM lifters.  The average after market cam for these engines is 600ish lift, they do that because that’s how you make big boy power.   And no I’m not very old, but I do understand how to make power on the LS/LT power plants, and keeping AFM lifters isn’t how you do it

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.