Jump to content
SAU Community
  • Welcome to SAU Community

    Welcome to SAU Community, like most online communities you must register to view or post in our community, but don't worry this is a simple free process that requires minimal information for you to signup. Be apart of SAU Community by signing in or creating an account.

    • Start new topics and reply to others
    • Subscribe to topics and forums to get email updates
    • Get your own profile page, build reputation and make new friends
    • Send personal messages to other members.
    • See fewer ads!

    Consider joining our newsletter for the latest content updates

    Click here to register


Crack Valve Seat


drgnball34
 Share

Recommended Posts

Had a punch up with my mechanic over the weekend. Unfortunately we are no longer friends either. He still maintains that whilst installing cams, he was not responsiable for snapping a valve causing for a engine rebuild. He has said that my car had a crack valve seat prior which caused the valve to snap, reason being was because my car was leaning/detonation.

My R34 has only done 50k kms. It was runing 100% perfect before. It has a avc-r and intercooler. I was under the impression that skylines rolled out of factory rich. Also that the factory boost cut prevents overboosting and therefore leaning.

My only option is to take this matter to a civil court. Could anyone please give me a reason as to how he snapped the valve or what casued it to snap? Am i correct about the boost cut and that they are rich from factory? I may need to talk to some workshops and get written statments to verify before i go to court.

Any help appreciated

Link to comment
Share on other sites

He is talking shit, they run rich as from the factory, otherwise `every other skyline would be burning exhaust valves, which valve did it drop? Not taking due care whilst installing cams can most certainly cause them or a valve to break, the valve seat was probably broken by the bent/broken valve.

Link to comment
Share on other sites

He is talking shit, they run rich as from the factory, otherwise `every other skyline would be burning exhaust valves, which valve did it drop? Not taking due care whilst installing cams can most certainly cause them or a valve to break, the valve seat was probably broken by the bent/broken valve.

thats exactly right.

have to take great care when installing cams as to where the pistons are.. otherwise you can tighten the cams down which push the valves(only some) down, if thee is a piston under it it wont push the piston it will just snap the valve or bend it, :(

Link to comment
Share on other sites

yes it was the exhaust valve im pretty sure. He heard a crack while bolting down the cams. Im assuming this was because the valve was seating ontop of a piston? Im alittle confused as to why only one valve snaped thou. If indeed the was timing off, wudnt more then one valve break/bend?

Link to comment
Share on other sites

Yeah it doesnt matter if it was just one, if the pistons were not left in the correct position then it could have only done the one.

I would think he would be liable in this case, it has broken whilst he was fitting the cams so he has to be responsible for that.

Link to comment
Share on other sites

If the valve timing was out there is a high chance the head of the valve may have been damaged during installation.

asking around on internet forums will be absolutly usless to you.

Your best option is to take the vehcile to another workshop who is prepared to put their neck out and help you. Not mnay places will be prepared to do this though.

The new workshop will tell you the bill will be forwarded to yourself. If the damage is found to be from the previous cam fittment then its up to you to take on the ex workshop on your own back. The new shop may not want to have anything to do with the legallities, they just want to be paid. If the vehcile ran fine when it left the workshop and you returned some time latter on you will not get anywhere, if the vehicle was returned straight to the shop and the concern raised then perhaps you will be listened to.

Its up to the repairer to prove he didn't break the valve and its up to you to prove that he did.

He may say its possible you over reved it prolonged which can cause valve problems, he may say he thought it was suspect and verbally informed you of the potential damage (even if he didnt)

Very hard for yourself to prove you didn't do the damage and with a vehicle such as a skyline the image of owner abuse is always there.

Best of luck with it. I have been shafted by arrogant customers a few times with the tribuneral. Some people just won't accept responcibility for their lack of respect in their vehicle.

If you know you did nothing wrong and feel you can prove it then give it a shot.

Link to comment
Share on other sites

Just for information purposes, yes the stock ECU drops timing by around 15 degrees once you go over ~12psi

Also the map for stock boost aims for an AFR of just under 10:1 at around 12.5psi this is about 11.2:1 very rich basically.

Finally if the car detects pinging it will reduce timing further.

Link to comment
Share on other sites

Yeah I wouldnt go and get another workshop involved thats just stupid and asking for trouble come payment time for the new workshop, keep it between you and him as that is who it concerns.

He heard a crack whilst putting the cams down ffs I mean that in itself tells you all you need to know. You have to confront him again and talk about it together, because legally he can simply lie and say it was detonation or whatever.

You wont be able to win this without really good concreate evidence which you just dont have nor can you get it really, as much I know its probably obvious that he has caused this, legally he can wriggle out of it more than one way.

Link to comment
Share on other sites

its very simple the car drove in normal, didnt leave driving, it was in the workshop to have cam's instaled and it all f**ked up, how is this your fault? my guess is he either f**ked up the cam alignment before remooving the cam's or he possibly put exhaust cam on inlet and vice versa? what kinda cam's went in it? did they need valve train stuff instaled also? personaly if i mess around with cylinder head stuff e.g cam's i rotate the motor slightly of t.d.c to prevent such things happening, in a court i dont like your chance's because your car has been *modified* even if it is ever so slightly im sure he can try get outa it.

Link to comment
Share on other sites

it has tomei poncams 260. No other valve train was installed.The head has been damaged to the point that there is not much of a seat left to even begin to tell if it was cracked. Damaged was on cylinder 6. If it was cracked wouldnt i be able to tell by the cylinder missing?

Link to comment
Share on other sites

if it had a cracked valve seat before hand then most definantly you would alteast notice a difference,id say on a near stock standard r34 with 50,000km someone has f**ked up... sounds like its let go and smashed a piston,

Link to comment
Share on other sites

Just for information purposes, yes the stock ECU drops timing by around 15 degrees once you go over ~12psi

Also the map for stock boost aims for an AFR of just under 10:1 at around 12.5psi this is about 11.2:1 very rich basically.

Finally if the car detects pinging it will reduce timing further.

Can any1 else confirm/verfiry this also? Hopefully some tuners

Link to comment
Share on other sites

You will find the engine was miss-timed to far and when he tighten the cam down the valves on number 6 kissed the top of the piston. He didn't wake up to it and kept tightening the cam until he heard the bang when the valve snapped. ( don't forget the other valve maybe bent)

You will find if you take the cYl head off you see the valve imprint ( broken one and the one next to it ) on the top of the piston.

Armed with this and a letter from an expert to say the probable cause you can go to the department of fair trading and have a win .

If I was you I would just front up and tell him that " iIwill take the to another shop have the cyl head off and they will se the valve imprint on the top of the piston ". Try to convince him that you then will take it to fair trading unless he agrees to pay for a top end rebuilt .

I wish you luck... I feel for you ..

Link to comment
Share on other sites

Head is taken off already. I just went and had a look at the piston. There is indeed dents in two places on the piston but it seems like their were caused from the piston smashing the broken valve up aganist the head. I will post pics of head and piston soon.

What im confused is that he heard a crack sound when bolting cams down. He apparently backed off and double checked that timing and everything else was fine then proceeded. Remember the engine never got put back together to be started, just cranked over only. And i was there and could hear a cracking sound every rotation or so. So the valve wasnt snap then yet. But the next day when he went to do a compression test to see if it bent, thats when it crunched.

Link to comment
Share on other sites

Bush mechanic. The moment he heard a bad noise especially after having done some major top end work he was MAD to not pull the head off to investigate it further.

As wrxhoon has said, the dents in the pistons are all the evidence you need. Damaged valve seats or not, you don't get valve train/piston interferance unless the belt is not correctly aligned.

Good luck sorting it out...

Link to comment
Share on other sites

post-27445-1166704224.jpg

There are indeed two dents...but looks like it was made from the broken valve geting smashed up aganist the head. The second valve is fine and from what i could tell not even bent. Thats where im alittle confused..Why only one valve was snapped instead of two??

Get this. The dick wont give me back my head until i pay him for the " work " his done!? What a prick huh? So cant post pics of the head just yet

Link to comment
Share on other sites

I would pay him the $200 for taking the head off and get your car out of there

Which brings the next question.... Ask him how he removed the head bolts and if he did it in any particular order. There is a bolt removal procedure so that you don't warp the head when unbolting it.

Chances are you will need to get the head lightly shaved to remove gasket bruising from the head, but you can do without having to get it crack tested along with the valve train rebuild etc.

Link to comment
Share on other sites

  • 5 weeks later...

I got the DOCEP to come out and inspect my car. All other valves and valve seats are fine, head is perfect and no sign of detonation. Timing was set correct otherwise all exhuast valves wud of been bent. He came to the conclusion that a valve seat had popped out!?....based on wot the mechanic suggested. They just dont pop out do they? Anyone heard of this happing? Its all theory. Argument is that only one valve snapped. Is there any other way that would cause only one valve to snap? Maybe the valve cap wasnt sitting down corretly? Any possible way that the rocker may have jammed?

I need help please!!!!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share



×
×
  • Create New...