Lifters Question
 

I have a 09 Silerado with the 5.3 V8. I have installed a CompCams cam with 224 int./228 exh. 0.534 int./0.537 exh and the valve springs recommended for the cam. I have taken my truck to the local dealer ship this morning to get a oil leak fixed and a O2 sensor replaced. The dealer ship told me that they want to change out the lifters in the truck because the computer is showing misfires. From what I nderstand from the guys at HP tuners, misfires are common when you put a cam like that in. What I don't understand is why they want to put new lifters in the truck. Can someone tell me whay they want to replace the lifters?

The dealer may think the false knock is coming from a bad lifter (and it may be)...Your pcm is probably picking up false knock from your knock sensor due to the cam swap ..Since you are n/a you can tune it to be less sensitive...iirc...but someone else may have a better answer..good luck

They want to replace your lifters because they think you have a factory cam and lifters that are defective. But surely you didn't change the cam and leave the AFM lifters? If you have the truck tuned properly it shouldn't be misfiring though.

I did leave the factory lifters in the truck. I didn't see replacing them since they only have 50K miles on them. On the misfire, I have no idea. I'm not detecting any knocks in the timing, plus I didn't up the timing after the cam was installed. It's still running the timing settings that I had set before the cam install and have had no problems with it. What benefit would I have on swapping the lifters? Also, they didn't tell me this until I was at the dealer ship yesterday evening picking up the rent-a-ride. They took the heads to a mechine shop to have them presure tested. Maybe that's were the misfire is coming from.

Sounds to me the typical knock that is had after a cam swap. Have the sensors turned down.. No reason to replace the lifters for a cam swap, unless there is a ton of miles on them... JMO

if they took the heads off already, why not get new lifters? they shouldn't charge you hardly anything for labor if the heads are already off

The DoD/AFM lifters are only meant for ~.500 lift. AFM is the system that shuts down 4 of the 8 cylinders during light load conditions.

The have a tendency to fail above .500 lift and hopefully they aren't putting new AFM lifters back in, but they most likely are... You need to get rid of AFM when using a cam like that and use standard lifters.

Just so you know, false misfires are very common after a cam swap due to the increased overlap and different crankshaft speeds than the PCM is expecting to see, the misfire counters usually need to be softened up, this is very common and normal.

Amen.

Here's a cam swap that I did a while back . . . it shows the differences in the lifters

http://www.youtube.com/watch?annotat...&v=0PkJne4OIb8