Hello, did a 6.2 swap in my Yukon 6 months ago. Have had a consistent tapping noise when cold that lasts for 10-15 minutes then the engine sounds good and normal. I have had piston slap in some other vehicles and it was always a more hollow sound that went away fairly quickly. This noise sounds more metallic in nature, which is why I am skeptical that it's piston slap. I am frustrated because I spent the extra money on the better parts to avoid exactly this issue. The truck has stock manifolds and y-pipe.


Setup is
L94 6.2
Cam Motion VVT cam
Johnson 2110 lifters (have tried .025, .050, and a hail mary .130 preload). .025 preload was awful. The .130 preload was just stock pushrods and it sounded the best but still there.
PAC 1219 springs


Cold

Warm

Sample piston slap video (30 seconds)

 

Your warm idle sounds pretty much just like my Silverado LC9. But it still has AFM. My vote is valvetrain but I'm no expert. The cold idle sounds a bit excessive.

 

Yeah it sounds close to stock stock warmed up.

The cold starts drive me nuts though. Never had a cammed vehicle sound this bad on cold starts, even with LS7 lifters.

 

Lifter bore clearance issue maybe?


https://ls1tech.com/forums/generatio...ifter-tap.html
https://www.corvetteforum.com/forums...0-install.html

 

#1 reason why you shouldn't start up a cold engine and take off driving. Are these the same engines that due to their VVT they can run on only four cylinders?

 

It's driven very easily. If I warmed it up to the point it had to be quiet before I drove it, I'd be idling in my driveway for 30 minutes every day.

VVT is variable valve timing, nothing to do with DOD which shuts off the cylinders.

 

I got you and I'm sure VVT has its place. Just not in anything I'll be building.

 

VVT is pretty harmless. It's AFM/DOD that causes untold problems.

 

VVT in a heavy truck is great. 30 extra ft/lbs down low. Throttle response is awesome. Retard the cam up top and there's no tradeoffs in a mild cam setup.

 

What oil are you running? I don't know how picky the VVT is with oil viscosities, but switching from a 5w-30 to an 0w-30 or 0w-40 may help.

 

I tried like 10 different oils, probably spent more on oils than just buying the GM caddy lifters which is what I am considering now.

Right now I am using 5w-30 redline oil, which is a group 5 synthetic with tons of zinc and moly.

Also considering deleting VVT and going with the 8620 cam motion cores just to rule out everything. Those cams were silent in my other setups. It's borderline undrivable right now because the primary use of this truck is to drive my son to school every day, so it doesn't even quiet down until I am back parked in my driveway after the return trip home.

You bring up a good point about VVT though, perhaps something is going on there with oil flow. An easy test would be if I had a cheap 3 bolt cam to toss in and test it out. I can swap cams on the truck in like 2 hours. Changing lifters is obviously much more effort.

 

What can I do without throwing money at the problem?

I am thinking of trying the stock VVT cam sitting in my garage. That will only cost about 40 bucks to swap in. Would hopefully rule out the cam itself being an issue, then I can focus on lifters?

 

Did you switch up oil viscosities or were they all different forms of 5w-30?

 

I tried from 0W-30 thin as water mobil 1 fuel economy to much thicker castrol 0w-40. Nothing made a difference.

Here it is fully warmed up, engine bay open. It sounds good like all my old cammed motors.

 

Here is one from January, sounds normal even with headers on it.

 

Here's what bad AFM lifters sound like. Sounds similar to mine IMO.

 

I resolved the issue by swapping the 2110 lifters for morel dropins. There is no tapping and oil pressure is 15 psi higher now. 36 psi from 21.

tried contacting johnson through their site but got no callback.

Im thinking johnsons have too much bore clearance. Im relieved it isnt the engine itself.

I spent almost 1000 chasing this issue, but thats the hidden price of modding.

 

Well said sir.

 

Thank you. Years back dealt with the issue of those whining cams comp/lunati kept sending out. There's always a risk with aftermarket stuff.

The thing with Johnson is I know they say you need to measure the lifter bore clearance, but realistically on a dropin lifter, mild cam setup, who is really doing that?