Need help

[Nickvincent987]

I have a 1988 ford ranger and it keeps burning valves in the same cylinder the timing is good and there is no vacuum leaks it’s not running lean what else could cause this

 

[alwaysFlOoReD]

What engine?
Any codes?

 

[pjtoledo]

corroded or clogged cooling passages causing hot spots near that valve? that's a long shot, but it's the best I can do this late at night.

 

[Nickvincent987]

Brunt valves

There are no codes and it’s a 2.9l

 

[adsm08]

Exhaust leak at the manifold gasket can burn exhaust valves.

 

[Bird76Mojo]

Are you using the same head and just having it rebuilt every time?

Burning the exhaust valve only?




GB

 

[Nickvincent987]

There is brand new gaskes at the manifold and the but the heads are brad new and yea just the exhaust is valve

 

[19Walt93]

Loose valve guide? I've seen 2.9's crack heads under the valve cover and the coolant ends up getting sucked into the cylinders by the pcv system.

 

[Bird76Mojo]

There is brand new gaskes at the manifold and the but the heads are brad new and yea just the exhaust is valve

Well, it's hard to make sense of this but I'm seeing: new exhaust manifold gaskets, heads are new, and just the exhaust valve is burning?


Besides a leak at the exhaust manifold, there can't be a lot more reasons to keep burning the exact same exhaust valves on brand new/rebuilt heads.


I do know the 2.9 is known to have problems with the cam journals/bearings wearing in an odd way if the mileage is high enough.

As mentioned by Walt, the 2.9's are very well known for cracking heads as well. It's usually in the same exact spot too. I've cracked/changed/cracked half a dozen heads on my old 2.9's and all cracked in the exact same spot. On 2 different blocks.

I suppose you could closely inspect your rockers and see if something is funky there. Also have a good look at your hydraulic lifters. Comparing measurements of your pushrods might also point to something.

Still, I'm thinking something's funky with the fuel system, or the cooling passages near that valve.



GB

 

[RonD]

Did you get new rockers with the heads?

Valves rotate each time they open
For exhaust valves this is very important so they don't get hot in one spot
A worn rocker can cause valve to stay in the same place and result is............wait for it......lol, yes burnt exhaust valve.

 

[Nickvincent987]

I motor only has 80,000 miles on it could an injector giving to much fuel burn a valve I didn’t get new rockers with the engine what should I look for

 

[Nickvincent987]

No new rockers the motor only has 80,000 on it coin a back ingector like that isn’t misting more like putting out a dribble of duke cause it to burn a valve because then I would have the right air fuel ratio making it run lean because it’s not a mist?

 

[RonD]

Since there is only one O2 sensor for all 4 cylinders then it is possible for a cylinder to run leaner or richer than the others, computer just opens other injectors longer to balance exhaust for oxygen level

But there would be other signs of a Lean burn, pinging/knocking would be heard often
And head chamber and piston top would show signs of that, pitting

Burnt exhaust valve is because the valve is not sealing the cylinder when it closes on its valve seat, simple as that.
Explosive gases, when cylinder fires, start to exit at that opening which eats away at the softer metal, the valve
Eventually no seal is possible and cylinder starts to misfire

Yes, lean burn causes higher heat in that cylinder, that's what causes the Pinging/Knocking
That heat can soften the valves BUT.....intake valve usually take the brunt of that because its softer metal than exhaust valve, it "tulips" from the heat, which does happen on the 2.3l


If bevel on valve seat and valve are not the same then poor seal happens(i.e. Valve job)
If valve seat is not being cooled by head coolant circulation, it can get a hot spot, causing poor seal
If valve isn't turning it can get a hot spot, causing poor seal


Valve stem should be flat on top, rocker should also have flat area so valve stem is free to turn, and roller rocker needs to be flat, if it sits at even a bit of an angle it will prevent valve from turning, like its pressing sideways on the of the stem not straight down

Weak valve spring is a long shot but not a no shot, lol

 

[Nickvincent987]

So the fact i have it straight pipes with holloes out cats probably isn’t helping and the pipe I have is like 3 inches so I should probably get a pipe that is more stock size