I was hoping it was OK and you were lucky on this one so I am sorry for the bad news but I also cannot imagine one tooth would matter. I mean there is a little slack either side of TDC when the exhaust is closing and the intake opens up isn't there.
Out of curiosity was the head also resurfaced bringing the valves a little closer? But then again if the valve was ground wouldn't it actually give it just a wee bit more clearance?
Please post some pictures of what you find when you get back into the motor. I'm hoping for you it can be saved.
S38 Possible Timing Issue
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JW in VaBeach
- Posts: 670
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- Location: Virginia Beach Va.
post topic
Anyone know the design valve to piston clearance at split overlap? It was my understanding that the 'one tooth off' condition was corrected prior to any attempt to start the engine. I know that the engine was rotated two complete revolutions by hand before an attempt to start it. If the damage is the result of improper cam timing [one tooth off] it would have resulted in damage to six pistons and twenty four valves. Were all valve train components returned to their original position at reassembly?
The head was milled, supposedly only .002 inch which is acceptable. Simply too much that is unknown to the forum. I told him in a P.M. that there appeared to have been valve to piston contact but having not been involved in the assembly process I was not in a position to say what went wrong or when. When I completed the assembly of mine, it ran flawlessly.
The head was milled, supposedly only .002 inch which is acceptable. Simply too much that is unknown to the forum. I told him in a P.M. that there appeared to have been valve to piston contact but having not been involved in the assembly process I was not in a position to say what went wrong or when. When I completed the assembly of mine, it ran flawlessly.
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theajinator
- Posts: 150
- Joined: Jun 08, 2012
- Location: Triad, North Carolina
When I timed everything initially, I kept the slack on the idler side when it should have been the tension side. This made the cam timing one-tooth retarded. We turned the engine over twice to verify timing was correct, but the tensioner had no pressure, so timing appeared to be correct. When we first started the engine, we heard valve tick from ONE valve and noticed that only five cylinders were firing. We immediately shut the engine down to verify timing. The engine ran at about 700rpm for a total of about sixty second, just enough time for the tensioner to build pressure. We reset the timing (which had discovered were a tooth retarded on), and spun the engine over with no plugs to see which valve was staying open and also checked clearances. Number eleven was the culprit. When rotating the engine with the starter and no plugs, the valve opened as normal but delayed when closing. As if there were insufficient spring tension or the valve were hanging in the guide. We decided to run the engine and see what happened. The longer it ran, the better it ran and after about ten minutes of driving, No. 6 had compression again. Valve noise went away, so I believed everything were fine. Apparently not. 
Ay, ya, yay ........ I have been off this forum for a bit. I really wish I had seen this thread sooner. This type of thing is exactly why I created my write up. 
You should read it. Link below.
https://docs.google.com/file/d/0B95IxHy ... FQcnM/edit
An S38 is a $10k-$15k rebuild. At $15k you get a MONSTER of an engine, but a stock $10k rebuild is still an S38.
You found out the hard way. Yes. Absolutely yes. Being one tooth off WILL kill your engine and a bent valve is not something you mess around with on a high revving engine. Lesson learned. You absolutely do not guess at anything with an S38.
Best of luck rebuilding. You must not cheap out on anything and you MUST pay extremely close attention when you re-assemble. Most importantly, you MUST know how to set the mechanical timing and valve clearances. Slightly goof anything else and it's an inconvenience. Goof on the valve timing and you end up where you unfortunately find yourself.
If you don't have a shop manual, below are links to a scanned version along with torque tables and an Excel spreadsheet to calculate your valve shims.
https://docs.google.com/file/d/0B95IxHy ... 9hSXM/edit
https://docs.google.com/file/d/0B95IxHy ... g3Ymc/edit
https://docs.google.com/file/d/0B95IxHy ... RhQXM/edit
Jose
You should read it. Link below.https://docs.google.com/file/d/0B95IxHy ... FQcnM/edit
An S38 is a $10k-$15k rebuild. At $15k you get a MONSTER of an engine, but a stock $10k rebuild is still an S38.
You found out the hard way. Yes. Absolutely yes. Being one tooth off WILL kill your engine and a bent valve is not something you mess around with on a high revving engine. Lesson learned. You absolutely do not guess at anything with an S38.
Best of luck rebuilding. You must not cheap out on anything and you MUST pay extremely close attention when you re-assemble. Most importantly, you MUST know how to set the mechanical timing and valve clearances. Slightly goof anything else and it's an inconvenience. Goof on the valve timing and you end up where you unfortunately find yourself.
If you don't have a shop manual, below are links to a scanned version along with torque tables and an Excel spreadsheet to calculate your valve shims.
https://docs.google.com/file/d/0B95IxHy ... 9hSXM/edit
https://docs.google.com/file/d/0B95IxHy ... g3Ymc/edit
https://docs.google.com/file/d/0B95IxHy ... RhQXM/edit
Jose
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JW in VaBeach
- Posts: 670
- Joined: Aug 23, 2008
- Location: Virginia Beach Va.
post topic
WOW!! had no idea that the S38, unlike other four stroke cycle internal combustion engines, can be so selective as to bend only one of 24 valves when rotated with cam timing "one tooth off".I suppose that the adjacent intake valve along with 22 others just got lucky.
Why only one of your valves got bent I don't know for sure. It could have to do with the interfernce and overall mechanical timing of the engine.
You say the mechanic was going to grind your valve stem because it was long. As close as the timing is on these engines, a long valve and one tooth off on the intake could be enough to bend your one valve. That sounds less lucky and more like bad planning and a lack of experience with close tolerance high revving engines.
I'm trying to help you and passing on what I learned the hard way. I documented the shit out of it, so that other would hopefully not make the same mistakes I did. It sounds like you don't want to hear it. If that's the case, then why are you in this forum asking questions?
Jose
You say the mechanic was going to grind your valve stem because it was long. As close as the timing is on these engines, a long valve and one tooth off on the intake could be enough to bend your one valve. That sounds less lucky and more like bad planning and a lack of experience with close tolerance high revving engines.
I'm trying to help you and passing on what I learned the hard way. I documented the shit out of it, so that other would hopefully not make the same mistakes I did. It sounds like you don't want to hear it. If that's the case, then why are you in this forum asking questions?
Jose
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mooseheadm5
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He did mention that it was possible that the machine shop grit blasted parts of the tappet bores. That could have contributed along with the timing issue.
Yes, it is possible to bend only one valve due to improper assembly/timing. Given the stack up of clearances, manufacturing tolerances, the fact that the valve clearance was not measured prior to starting the car, the incorrect timing, poor machine work etc. it is absolutely possible. Everyone here that is experienced as a tech has seen motors bend just one or two valves when put together improperly.
Yes, it is possible to bend only one valve due to improper assembly/timing. Given the stack up of clearances, manufacturing tolerances, the fact that the valve clearance was not measured prior to starting the car, the incorrect timing, poor machine work etc. it is absolutely possible. Everyone here that is experienced as a tech has seen motors bend just one or two valves when put together improperly.
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JW in VaBeach
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- Location: Virginia Beach Va.
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Moose I was building engines when you were shitting yellow. Take that tech shit somewhere else. Obviously something was amiss here however the "one tooth off" scenario in and of itself is not an explanation.
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mooseheadm5
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Given that everyone here except you told him to stop driving the car because we all knew the valve was bent and that bad shit could happen, I'd say you can stuff it. You did him absolutely zero favors telling him what he wanted to hear instead of what he needed to hear. You should be ashamed of yourself giving such careless incorrect advice.
I'd also like to point out that you don't actually know whether or not any of the adjacent valves were kissed by the pistons unless you check how well they seal.
I'd also like to point out that you don't actually know whether or not any of the adjacent valves were kissed by the pistons unless you check how well they seal.
Geez...... this is a no brainer.
No way in hell do I tell someone to "just drive" an S38 making weird engine noises. I can't believe anyone with knowledge/experience about BMW engines would seriously say that.
If you KNOW a valve is sticking, you don't run the damned engine. The top end on these is upwards of $5K to rebuild and that is if your castings are ok. If the OP had stopped driving the thing and fixed the valve issue it's less than $300 in parts and whatever labor costs he incurs.
Instead, he did exactly what JW recommended and now he is looking at what? Maybe a damaged head, piston, rod, main bearings .... who knows. This isn't some shitty pushrod V-8 you can just blow up and replace with a nice crate engine for less than $5000. These things are ridiculously expensive when things go wrong.
OP - Not slamming you, just trying to inform. The people offering their opinions don't have to pay to fix the damage. This is a good example of carefully judging who you listen to. Yes these kinds of forums are a great resource, but remember what they say about opinions.
Best of luck on your engine quest.
Jose
No way in hell do I tell someone to "just drive" an S38 making weird engine noises. I can't believe anyone with knowledge/experience about BMW engines would seriously say that.
If you KNOW a valve is sticking, you don't run the damned engine. The top end on these is upwards of $5K to rebuild and that is if your castings are ok. If the OP had stopped driving the thing and fixed the valve issue it's less than $300 in parts and whatever labor costs he incurs.
Instead, he did exactly what JW recommended and now he is looking at what? Maybe a damaged head, piston, rod, main bearings .... who knows. This isn't some shitty pushrod V-8 you can just blow up and replace with a nice crate engine for less than $5000. These things are ridiculously expensive when things go wrong.
OP - Not slamming you, just trying to inform. The people offering their opinions don't have to pay to fix the damage. This is a good example of carefully judging who you listen to. Yes these kinds of forums are a great resource, but remember what they say about opinions.
Best of luck on your engine quest.
Jose
Here's my opinion:
There are always guys telling you to do both options on the internet. And the majority always being right is not true either. For instance, I'm still on original timing components to my knowledge at 215k, ignoring what the large majority of people have told me to do, however some senior BMW mechanics have told me "don't worry about it, just drive it" and not to buy into the internet scares. I also plan to make it until an engine rebuild that I hope I will be doing in the near future, technically meaning that while I didn't do the conservative option, I did the correct option.
Also, I think it's really easy to jump on the conservative bandwagon. If you're wrong, so what, you never have to admit to being wrong because you can always tell yourself "it was the safe thing to do" even if he had pulled apart the engine and everything was fine.
But to take the non-conservative route and tell him to just drive the thing with the consequences of being wrong on an S38... you better be an s38 expert AND totally sure of your advice.
There are always guys telling you to do both options on the internet. And the majority always being right is not true either. For instance, I'm still on original timing components to my knowledge at 215k, ignoring what the large majority of people have told me to do, however some senior BMW mechanics have told me "don't worry about it, just drive it" and not to buy into the internet scares. I also plan to make it until an engine rebuild that I hope I will be doing in the near future, technically meaning that while I didn't do the conservative option, I did the correct option.
Also, I think it's really easy to jump on the conservative bandwagon. If you're wrong, so what, you never have to admit to being wrong because you can always tell yourself "it was the safe thing to do" even if he had pulled apart the engine and everything was fine.
But to take the non-conservative route and tell him to just drive the thing with the consequences of being wrong on an S38... you better be an s38 expert AND totally sure of your advice.
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mooseheadm5
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There was no jumping on the bandwagon here, though. The majority opinion was given by experts given the evidence that quite obviously pointed to there being a problem with at least one valve after the rebuild. Valves don't get super loose then tighten up if everything is fine, it was like that because it got bent one way or another and then the piston bent it back into shape.
As for the S38 timing chain issue, it is more a game of odds than anything else. The guides will all eventually fail, that is a given. When they fail is determined by the usage, type of oil, heat cycling, etc. Some people think it is just fine to leave it be and hope for the best. While that is a school of thought, it will eventually lead to catastrophic failure of the timing chain guide rails. Maybe not in 200k, maybe not even 300k, but I have seen it happen at 100k, some earlier. I know a guy with a 150k M6 that needs guide rails now. He caught it before the chain skipped time, but you may or may not be that lucky if you wait. In the case of the S38 timing chain guide consensus is to err on the conservative side simply because of the high cost of failure. The case of AJ's motor, erring on the side of caution doesn't even enter into it. When all the signs point to a damaged internal component that can wreak more havoc by letting it go, you stop driving the car and take apart the motor, just like it someone were to tell you that a ball joint in the front end had 2 inches of play you wouldn't drive the car and hope it would get better. The overwhelming evidence says repair it immediately. The conclusions reached in this thread by Kyle, Winfred, and I were evidence based, not wild guesses and jumping on any sort of bandwagon.
As for the S38 timing chain issue, it is more a game of odds than anything else. The guides will all eventually fail, that is a given. When they fail is determined by the usage, type of oil, heat cycling, etc. Some people think it is just fine to leave it be and hope for the best. While that is a school of thought, it will eventually lead to catastrophic failure of the timing chain guide rails. Maybe not in 200k, maybe not even 300k, but I have seen it happen at 100k, some earlier. I know a guy with a 150k M6 that needs guide rails now. He caught it before the chain skipped time, but you may or may not be that lucky if you wait. In the case of the S38 timing chain guide consensus is to err on the conservative side simply because of the high cost of failure. The case of AJ's motor, erring on the side of caution doesn't even enter into it. When all the signs point to a damaged internal component that can wreak more havoc by letting it go, you stop driving the car and take apart the motor, just like it someone were to tell you that a ball joint in the front end had 2 inches of play you wouldn't drive the car and hope it would get better. The overwhelming evidence says repair it immediately. The conclusions reached in this thread by Kyle, Winfred, and I were evidence based, not wild guesses and jumping on any sort of bandwagon.
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rmiddendorf
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I get tired of this crapstorm bunk when you guys get your egos hurt when things don't go your way.
And furthermore I know Moose and I fully trust his comments. Few people here know these cars better than MooseheadM5 and for you to come in here and act like this is completely unnecessary.
Nice personal slam when it was not necessary. Take your unfounded comments somewhere else please.JW in VaBeach wrote:Moose I was building engines when you were shitting yellow. Take that tech shit somewhere else.
And furthermore I know Moose and I fully trust his comments. Few people here know these cars better than MooseheadM5 and for you to come in here and act like this is completely unnecessary.
Last edited by rmiddendorf on May 17, 2013 3:54 PM, edited 1 time in total.
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rmiddendorf
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In any situation you have to decide how much to weight which advice. You took your mechanic's opinion and it was the right choice for you. I'm in a similar boat where my mechanic talked me out of the timing component job for at least another year, although I'm most concerned about the plastic timing guides. Plastic is not indestructible. Even as the car heat cycles each time it wears a little more. And the timing chain tensioner's condition and replacement interval also play into this. My car still had an operable tensioner when I preemptively replaced that part so I assume the chain didn't bang up my guides excessively yet.Randomg wrote:Here's my opinion:
There are always guys telling you to do both options on the internet. And the majority always being right is not true either. For instance, I'm still on original timing components to my knowledge at 215k, ignoring what the large majority of people have told me to do, however some senior BMW mechanics have told me "don't worry about it, just drive it" and not to buy into the internet scares. I also plan to make it until an engine rebuild that I hope I will be doing in the near future, technically meaning that while I didn't do the conservative option, I did the correct option.
Also, I think it's really easy to jump on the conservative bandwagon. If you're wrong, so what, you never have to admit to being wrong because you can always tell yourself "it was the safe thing to do" even if he had pulled apart the engine and everything was fine.
But to take the non-conservative route and tell him to just drive the thing with the consequences of being wrong on an S38... you better be an s38 expert AND totally sure of your advice.
Other deciding factors are how much money you already have in the car as well as the importance of keeping it original. So the decision is ultimately unique to all of us and our individual situations.
What I can say for sure is that when I took apart my engine at 135K, the slider rails were at least half eaten through, along with heavy wear at the contact points. The plastic guide also had about 2 inches worth of the bottom broken off. Just look in my write up and you can see for yourself.
Could I have gone longer on the parts? It was running fine, so I am sure I could have. Would I choose to re-assemble an engine with parts worn out worn like that? Not on your life. That would be a crime on any engine, especially an S38. Yes it's ultimately a choice, but If there is one policy I go by it is "do it right the first time".
Jose
Could I have gone longer on the parts? It was running fine, so I am sure I could have. Would I choose to re-assemble an engine with parts worn out worn like that? Not on your life. That would be a crime on any engine, especially an S38. Yes it's ultimately a choice, but If there is one policy I go by it is "do it right the first time".
Jose
I was talking from OP's perspective. If I'm new to a forum I tend to assume a few people know what they're talking about and others jump on the bandwagon. It's a pretty common pattern across the internet. Kyle's posts definitely didn't feel like they were coming from an s38 expert. OP could have done some searching to see how knowledgeable each of you guys are I guess.mooseheadm5 wrote:There was no jumping on the bandwagon here, though. The majority opinion was given by experts given the evidence that quite obviously pointed to there being a problem with at least one valve after the rebuild. Valves don't get super loose then tighten up if everything is fine, it was like that because it got bent one way or another and then the piston bent it back into shape.
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mooseheadm5
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Kyle in NO
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rollcentre
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Da_Hose wrote:Ay, ya, yay ........ I have been off this forum for a bit. I really wish I had seen this thread sooner. This type of thing is exactly why I created my write up.
https://docs.google.com/file/d/0B95IxHy ... FQcnM/edit
An S38 is a $10k-$15k rebuild. At $15k you get a MONSTER of an engine, but a stock $10k rebuild is still an S38.
You found out the hard way. Yes. Absolutely yes. Being one tooth off WILL kill your engine and a bent valve is not something you mess around with on a high revving engine. Lesson learned. You absolutely do not guess at anything with an S38.
Best of luck rebuilding. You must not cheap out on anything and you MUST pay extremely close attention when you re-assemble. Most importantly, you MUST know how to set the mechanical timing and valve clearances. Slightly goof anything else and it's an inconvenience. Goof on the valve timing and you end up where you unfortunately find yourself.
If you don't have a shop manual, below are links to a scanned version along with torque tables and an Excel spreadsheet to calculate your valve shims.
https://docs.google.com/file/d/0B95IxHy ... 9hSXM/edit
https://docs.google.com/file/d/0B95IxHy ... g3Ymc/edit
https://docs.google.com/file/d/0B95IxHy ... RhQXM/edit
Jose
you da man!Danks fer dees! 
Da_Hose wrote:Ay, ya, yay ........ I have been off this forum for a bit. I really wish I had seen this thread sooner. This type of thing is exactly why I created my write up.
https://docs.google.com/file/d/0B95IxHy ... FQcnM/edit
An S38 is a $10k-$15k rebuild. At $15k you get a MONSTER of an engine, but a stock $10k rebuild is still an S38.
You found out the hard way. Yes. Absolutely yes. Being one tooth off WILL kill your engine and a bent valve is not something you mess around with on a high revving engine. Lesson learned. You absolutely do not guess at anything with an S38.
Best of luck rebuilding. You must not cheap out on anything and you MUST pay extremely close attention when you re-assemble. Most importantly, you MUST know how to set the mechanical timing and valve clearances. Slightly goof anything else and it's an inconvenience. Goof on the valve timing and you end up where you unfortunately find yourself.
If you don't have a shop manual, below are links to a scanned version along with torque tables and an Excel spreadsheet to calculate your valve shims.
https://docs.google.com/file/d/0B95IxHy ... 9hSXM/edit
https://docs.google.com/file/d/0B95IxHy ... g3Ymc/edit
https://docs.google.com/file/d/0B95IxHy ... RhQXM/edit
Jose
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theajinator
- Posts: 150
- Joined: Jun 08, 2012
- Location: Triad, North Carolina
Thanks for the tech info, Jose. As for my current S38, I'm very sad about losing that engine. I've become lucky enough to find a used engine in great shape with lower mileage. I'm going to be extremely thorough when putting this one back together.
As for my old engine, I'm pretty sure that the valve was hanging up in something. We'll see what happens when we get it put back together. Stay tuned.
As for my old engine, I'm pretty sure that the valve was hanging up in something. We'll see what happens when we get it put back together. Stay tuned.
Great, Ajin! The blocks on these things are really tough and well built. Its the top end that really gives me worry. I have thought of hunting down a spare engine, just for good measure.
The mechanical timing was really fiddly to get right and there is no way to test other than just cranking it when you believe you have it right. The exhaust can be off, but the intake is unforgiving. In my how-to I did my best to explain exactly what I was doing, step-by-step.
Let me know if I can help and good luck.
Jose
The mechanical timing was really fiddly to get right and there is no way to test other than just cranking it when you believe you have it right. The exhaust can be off, but the intake is unforgiving. In my how-to I did my best to explain exactly what I was doing, step-by-step.
Let me know if I can help and good luck.
Jose