Low compression, p0303

1MZ FE I have low compression in cylinders 3 and 5. Upon valve clearance inspection the exhaust clearance was at .006 compared to a .010-.014 spec. The head was a remanufactured one and they drove it like this for 30k mi. Any chance the exhaust valves are burnt? There is air coming out exhaust at tdc at 90psi test. Doing official leakdown test later today. Trying to avoid pulling the head yet.

 

There is a quite reasonable chance the exhaust valves are burnt. To confirm without pulling the head I would run a borescope into the cylinder. You might have to take the cylinder off tdc and open the valves for a good look all around it

 

Good chance it is burnt, but either way, if all looks good under the V/C and very low compression, then it sounds like you don't have much choice other than to pull the head...
Could smack the end of the valve stem to make sure the valve is not stuck open any...

Possible use a camera and take a look...

You could also run some Marvel Mystery Oil in the engine to see if it frees anything up, but I think you just need to pull the head and fix the issue...

 

Thanks for your advice. I dont have a borescope but could be nice in this situation.
Here is summary of leakdown test.
Cyl 1 6%
Cyl 3 38%
Cyl 5 15%

pulling the head next.
Will post a photo if I find anything interesting.

 

Probably going down the right rabbit hole but....
Why not correct those valve lash & do a quick decarbon with water & ATF through the intake & do a quick Italian tune-up / hot-lap making certain you just dont have carbon on the backside of the valves...
Nothing to lose...

 

Yeah good point Im taking header off first then can see how much gunk is behind valve.

 

I would definitely check the other head also, heck If I pull one, I'm pulling both and having them both decked and checked, valve job on both to keep everything balanced...

 

Cylinders 1 3 and 5 exhaust side. 3 has some crap in it, and 5 looks overheated.

 

are those cracks at the bridge between the valves or just a normal seam?
My point was to do the decor before tearing down, sometimes could be an easy fix. if valves are hanging open & not seating correctly but looks like youre going all in...

 

looks like a chip in one of valve sealing areas, and head gasket material in zoomed out photo. These borescopes are nice. Shoulda bought one years ago.

 

I cant say that I see anything youre describing in the pics & I did engine work for a living...
im not saying youre wrong, just dont see it..

ide also be looking at the inside edge of the cylinder walls for severe vertical scoring,
Thats always an indicator that teardown will be a waste of time & resources...

 

Yeah my eyes don't see what yours does, pictures of a screen rarely come across clear it seems, for me anyway... If you think you can see the head gasket, well then the head has to come off anyway cause you should not be able to see the head gasket poking out... lol

The 2nd pic, still can't see it clearly, looks like a carbon flake...

 

4x
Can you elaborate on what you think you see in the pics?
Not seeing anything....

 

Not sure what this little whatever is?

 

Looks like carbon to me, I am guessing though that is what the OP described as head gasket...

 

burnt valve one on top. I have a light in exh port you can see valve stem.

those flakes were indeed carbon on cyl wall edges up top. Cyl looks good all honed marks still there.

 

Yep, time to send both heads out for a deck and check and valve job with new valve(s)...
You can install the spark plugs and then pour some gas in the 5 remaining combustion chambers to see if any more valves are leaking, the one with the burnt valve won't work due to it already leaking, but check the other 5 cylinders...

I wouldn't mind seeing a good picture of all 3 chambers together for each head...

 

burned also or just debris?

 

Carbon goop... Need to clean up really good, or just take them to the machine shop and they can do any repairs needed...

 

they have to visit the machine shop, you dont just want to throw a valve at it....
way too much work at this point to play games...
a good machine shop will put good parts in it, & get rid of the budget garbage the engine rebuilders used...
hardened valves & seats...
Well atleast that's. what the machine shop ive use does...