Burnt Ring Cylinder #4

[BSouders80]

I had a whipple installed on my 2014 Raptor a few months ago. Truck had around 75k miles on it. Now sitting around 82k. I started feeling a miss, so I took it to a shop. Their scanner showed misfire cylinder 4. Logged at high rpm they said.

They did a leak down test and cylinder 4 is not holding. They checked the valve train and all looks good.

So it looks like the rings on cylinder 4 may be toast.

So how big of a rebuild am I looking at? If I’m rebuilding, I want to upgrade internals to hold the whipple.

What do you suggest?

Thanks.

Brian

 

[MurderedOutSVT]

At 82K I would say minimun total bottom end. This also would make keeping an 82K top end questionable. Not sure about rebuild parts but complete engines are ver difficult to come by. Took me months to find an 80K motor when mine went

 

[TomDirt]

So no valve spring damage? This motor has had documented issues with valve springs breaking, which can do some other damages.

 

[BSouders80]

I’ll ask the shop to double check the valve springs.

 

[BSouders80]

The mechanic told me that he pulled all of the rocker arms off and shot air into the cylinder. 95% he said leaked through to the crank case.

 

[BSouders80]

Anyone else have input on this?

 

[Canuck714]

So does it run ok and just miss at high RPM or is it missing all the time and running rough?

Normally I would suspect the cylinder pressure is leaking past a valve, not blowing past the piston into the crank.
Just because he pulled the rockers, doesn't mean the valve is fully seated in the head. It could still be a blow by at the valve seat.
Are they 100% certain that they are pressurizing the case?

Not questioning their ability to perform a leakdown, but if you are only able to hold 5% that usually means a hole in the piston or a melted ring land to get that much air in the case.
I'd pull the cylinder head off and have a look.

 

[BSouders80]

I noticed the miss at low rpm's (idle). Slight shaking. But prior to that, where under a moderate load in high gear on the highway, I'd hear a rattling sound. As soon as I'd let off of the throttle, sound goes away. I first noticed it pulling a trailer loaded with a car, going up a slight incline hill. I could duplicate the sound with no trailer, putting my truck in manual on the highway running around 50 mph. At WOT, you can hear the noise come on steadily louder as speed increases slightly. I've got a video on here that I posted.

The guy doing the work has been a mechanic for over 20 years, and is pretty good at what he does. I double checked with him just now. He said that he shot air in the cylinder and 95% leaked through to the crank case. He took the rocker arm shaft off. For the pressure to leak through to the crank case, wouldn't the valves have to be sealed?

 

[mprice1234]

Sorry to hear your down with engine issues, sounds like big $$$ whatever the issue is.

 

[rschap1]

I would think mechanic's next step is that head off.
That should show what the issue is one way or another.
Diagnose and go from there.
If it is in fact a ring, may as well refresh the bottom end along with whatever needed.
Met another owner a few weeks back at Bronco Takeover on Silver lakes Sand Dunes... he told me about his new 6.6.... would go good with your supercharge

Always easier spending someone else's $$$

Good luck with the fix ! ! !