what's a good way to tell the difference between a bent vale and a stuck/dirty valve as the cause of zero cylinder compression WITHOUT pulling the head?
What's a good way to tell the difference between a bent vale and a stuck/dirty valve as the cause of zero cylinder...
Jace Butler
Anthony Garcia
Why would you think you'd bent a valve?
Adam Reyes
started car after finishing up a major engine procedure which involved re-timing the engine.
I'm almost certain it was timed pretty much perfectly but i want some way to verify it.
the zero compression is on only one cylinder (of 8) and it causes the cylinder to always misfire, the ECU disables fuel to it
however it seems like valve bending can be so subtle that the only way to tell is to pull the head and very VERY carefully examine the valve seating
Nicholas Gomez
oh and the engine idles wonderfully minus one cylinder doing nothing, and all the other cylinders have fine compression
Andrew Long
Firstly do you even know if your engine is interference?
Secondly check NOW if your cam timing is correct.
Wyatt Jackson
it is most definitely an interference engine
for timing there's special tools which lock the cam shafts in place, and TDC is when the cylinder one cam lobes are pointing 45 degrees up sort of towards eachother. I've done plenty of rotations by hand and yes they do align like that in time with the crankshaft TDC as they should.
Carson Ward
If the valve was just dirty it wouldn't have zero compression. Your valve is fucked my dude.
Ian Butler
those valves looked fucked either you just need some valves or a new head with a set of valves.
Brayden Brooks
Well the best method is to count teeth - that way you know for sure, but if you're confident the cam timing is correct then it's very unlikely you have a bent valve.
Valves don't just bend themselves and unless you're running very fine tolerances on your race engine your timing shouldn't step out far enough for any contact with the piston.
Jaxon Ross
Another thing it could be is an incorrectly adjusted valve rocker. If it's too tight you could be leaving the valve open a bit all the time.
Anthony Perry
Or if it's too tight you might have bent your valve...
Aaron Rodriguez
that's actually a good question. I was going to tell you to get a compression test but both will have the same result. I think you might as well pull it off and check for yourself
Austin Williams
You can't really, you could maybe check the clearances between the valve lifters and the cam depending on what setup your engine uses.
Tripfaggot so desperate to spread his shitty opinion he doesn't even read the thread.
Colton Watson
think if the timing was off youd have problems on all cylinders.
Nolan Walker
Remove rockers
Gently tap on the valve stem with a dead-blow mallet.
You should be able to feel it open just a bit
If it is bent they tend to stay open
>it does not mater; you are going to end up pulling the head....
Oliver Evans
Why have you ruled-out hole in piston?
Cooper Parker
>Diying a timing belt when you aren't an expert
Congrats, you fucked the engine. Should've paid a professional
Samuel Evans
nah, there's a specific set of tools you use for timing which locks the cams and the crank and various other bits, and you do a series of things after it's timed to verify it's timed (things line up), which i did and they lined up perfectly
Leo Edwards
Yet it still doesn't work....
Michael Reyes
Have you even read the previous posts?
The engine works fine except for cylinder one, which come to think of it if the valve is fucked up because of incorrect timing I'm quite it would have fucked all other valves.
Jason Murphy
>valves
Jack Adams
make/model/engine
if not, what kind of timing set up and how are the valves opened/adjusted?
Evan Butler
You're not wrong. If your timing was off enough to bend your valves, you'd almost certainly have issues on all cylinders. You'd also know very quickly after starting it, as it would make one fucking hell of a racket.
>t. My old 944 blew the timing belt
Unless you turned your cam individually of the crank using a ratchet before locking it at TDC, I dunno how you could bend just a single valve and leave the others unscathed.
Are you running hydraulic lifters? In some cases, a collapsed or sticky lifter could give your valve enough play to not fully close all the way.
Hudson Morris
Timing a cam isn't rocket science.
Maybe that's how they do things on these new Variable Valve Timing engines but that sounds like a stupid way to do it.
Option 1:
>Count the teeth
Option 2:
>Pull the rocker cover off and time it that way
Mind you I'm not entirely sure which piston will be "on the rock" at TDC on a V8 but surely one of the cylinders will be.
Oliver Peterson
looks like your valves got hot hot and valve lash caused the seats to get pounded out need to cut new seats in and face them
Carson Edwards
also forgot to mention your valve guides are clapped out so need guides installed as well
Grayson Price
but what does your checking account look like?
David Baker
get a leakdown test kit and fill the cylinder with air, then take the spring off and twist the stem.
Ayden Smith
Either way the head has to come off for that
Benjamin Hall
didn't think this thread would get much attention
bmw 540i M62tu
it has the vanos system which is indeed a form of VVT
i just did a leakdown test of cyl 3 today while it was at TDC compression stroke and confirmed whatever is wrong, it's an issue on one of the exhaust valves, could hear the air escaping with my ear to the muffler. no sound from the throttle body meaning not intake valves
this is super weird because
>it's only one cyclinder, cyl 3
>using a borescope, the exhaust valves seem to be seating the same as on the other cylinders, they look to be at about the same level when fully closed
>if you mess up timing it'll bend valves BUT it's usually the intake valves that get fucked because the vanos unit is only on the intake cam, the exhaust cam is "dumb" in that sense.
can't get the spring off without popping the camshaft which means pulling the timing chain off it which will put it out of time and I'll need to re-time the engine
have a video of borescoping three cylinders (3 is the bad one, 2 and 1 are fine) and the leakdown of 3 and 1
youtube.com
Jace Foster
also
>this was originally a misfire on cyl 3 after i started the car after the big job, and i didn't hear any excessive noise indicating a bent valve on that start up. it just jumped to life but i could tell it was misfiring by the vibrations and the exhaust note
Sebastian James
How do I learn about what is going on ITT? Where can I start?
Carson Rodriguez
Is there any chance it's your lifters?
Are they shim type? Did you fuck with the shims?
Are they hydraulic? Is it possible they are stuck fully open?
Easton Foster
non hydraulic and no shims, here's an actual video of someone putting valves in the head of this engine
youtube.com
Charles Mitchell
>no valve adjustment
I didn't know that was possible, are you sure they aren't hydraulic? Looks like a typical hyrdo bucket setup.
Nathaniel Fisher
Owen Perry
i don't believe they are but maybe it's a specific form of hydrauling i'm not thinking of
there's a cap on top of the valve spring which is what the cam actually pushes on
Landon Campbell
This is what hydro buckets normally look like, mind you solid buckets and shim under buckets don't look much different.
Did you mess around with the buckets at all? Remove them?
Jaxson Cooper
no, didn't even remove the cam shafts, and yes that's exactly what the caps look like so in that case it is indeed hydraulic lifters with buckets
this is what the assembly looks like
James Torres
If you’ve owned your car from new and looked after it like it’s your baby it’s one story. You know exactly what’s going on, even in the engines internals
Joseph Bennett
Well I do wonder if it's possible the hydro (assuming) lifter is stuck........?
But I suppose the only way to check would be to remove the camshaft entirely (make sure you don't snap it) and do the leak down test again.
It's a lot of work for only eliminating one possibility but then i'd do that before I'd take the head off again.
Ethan Reed
>using a borescope, the exhaust valves seem to be seating the same as on the other cylinders
Doesn't look like that at all to me. That looks like the valve is open and you can see the valve stem. Pic taken from cylinder 3, at 1:35 in the video.
Also, when hydraulic lifters/buckets fail, they produce LESS lift (meaning "more closed" valve) than a proper one.
Liam Foster
pretty sure that's just some oil because that valve isn't one of the exhaust valves, it's one of the intakes
and as show in the leakdown test later, the intake valves are sealing fine.
the exhaust valves on cyl 3 become visible at 1:55
Connor Bennett
>being this scared to just pull the fucking head off