Paul Neubauer
Well-known member
Are all the pistons still moving?
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Spiffy
Well-known member
- Thread starter
- #32
These are all great ideas.
If the sprocket split wouldn't the timing change all the time or worst case like that photo where half of the sprocket is missing. Wouldn't the chain and cams stop turning when it got to the missing teeth?
Or maybe a severed keyway. The sprocket would just spin and keep changing timing.
I will check total timing tonight to see how far it's off.
I know by bumping the starter if the keyway was missing the inertia of the crank to timing chain woukd cause it to spin but it doesn't. The chain and cams move in unison to the engine.
I know I can figure this out by looking behind the cover but that's a lot of work in very tight spaces. First thing I have to do is scope the valves. If they are hit I'm not going any farther in teardown. I'm just going to pull engine and replace. This truck is my money maker. I'm trying to be efficient.
Bent valves mean engine out.
Stretched chain means I continue to tear it down . I don't want to tear it down only to find the sprocket gauled up the crank beyond service.
I'm betting stretched chain. Cold crank bumping means chain tentioner was loose. No oil. Loose chain jumped sprocket.
But to have all cylinders sitting on the compression stroke with a valve open is perplexing.
Really I only have to scope one cylinder. I have a rather excellent scope I use for lycoming engine inspection. It can pick up heat spots around valves when pilots consistent run it too rich. Or zoom in to see if the valve guides are worn causing mushrooming of the valve seat.
If the sprocket split wouldn't the timing change all the time or worst case like that photo where half of the sprocket is missing. Wouldn't the chain and cams stop turning when it got to the missing teeth?
Or maybe a severed keyway. The sprocket would just spin and keep changing timing.
I will check total timing tonight to see how far it's off.
I know by bumping the starter if the keyway was missing the inertia of the crank to timing chain woukd cause it to spin but it doesn't. The chain and cams move in unison to the engine.
I know I can figure this out by looking behind the cover but that's a lot of work in very tight spaces. First thing I have to do is scope the valves. If they are hit I'm not going any farther in teardown. I'm just going to pull engine and replace. This truck is my money maker. I'm trying to be efficient.
Bent valves mean engine out.
Stretched chain means I continue to tear it down . I don't want to tear it down only to find the sprocket gauled up the crank beyond service.
I'm betting stretched chain. Cold crank bumping means chain tentioner was loose. No oil. Loose chain jumped sprocket.
But to have all cylinders sitting on the compression stroke with a valve open is perplexing.
Really I only have to scope one cylinder. I have a rather excellent scope I use for lycoming engine inspection. It can pick up heat spots around valves when pilots consistent run it too rich. Or zoom in to see if the valve guides are worn causing mushrooming of the valve seat.
Captain Dirty Beard
Well-known member
It only takes 6 revolutions of the engine for the timing to be off, and piston to valve tappy tap.
I bet you will find that all of the intake valves are bent, unfortunately. I hope Im wrong
Spiffy
Well-known member
- Thread starter
- #35
?I hope your wrong too.
Why do you think it's intake? I listened to the intake manifold and didn't hear anything. That's what I do during a compression test on aircraft engines. I listen for leakage on both the intake and exhaust. If exhaust we tap on the valve with a hammer to feel the movement and see if valve is stuck. I couldn't get my ear up the exhaust and turn the key at same time.
Also wouldn't i hear the tap tap tap ?
Why do you think it's intake? I listened to the intake manifold and didn't hear anything. That's what I do during a compression test on aircraft engines. I listen for leakage on both the intake and exhaust. If exhaust we tap on the valve with a hammer to feel the movement and see if valve is stuck. I couldn't get my ear up the exhaust and turn the key at same time.
Also wouldn't i hear the tap tap tap ?
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FaaWrenchBndr
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Once again, the statement was made with the preface of, there has to be valve train damage or a chain jump.
Without that, its IMPOSSIBLE
Last edited:
Spiffy
Well-known member
- Thread starter
- #37
I know i need to physically check the chain to know for sure and I won't check if I see signs of piston to valve collision. And I'm definitely not arguing with ya all.
But my intrest is, can a chain be off enough to hold all cylinders in a state of no compression.
I found this to be very very interesting. This is from that new DeepSeek AI. I'm curious to see if anyone believes this.
If I'm off that far I can't believe the pistons didn't hit the valves during the chain slippage journey.
DEEPSEEK REPLY...
To determine how far the camshafts need to be out of sync (in degrees) to cause **all cylinders to have at least one valve open** on a Ford 3.5L EcoBoost engine, we need to consider the engine's valve timing and the relationship between the crankshaft and camshafts.
---
### **Key Concepts:**
1. **Crankshaft Rotation**:
- The crankshaft completes **720 degrees** of rotation for a full engine cycle (intake, compression, power, exhaust).
- The camshafts rotate **360 degrees** during the same cycle (since they turn at half the speed of the crankshaft).
2. **Valve Timing**:
- The intake and exhaust valves open and close at specific points in the crankshaft's rotation.
- The exact timing depends on the engine's design, but typically:
- **Intake valves** open slightly before Top Dead Center (TDC) on the exhaust stroke and close after Bottom Dead Center (BDC) on the intake stroke.
- **Exhaust valves** open before BDC on the power stroke and close after TDC on the exhaust stroke.
3. **Overlap Period**:
- There is a brief period called **valve overlap** where both the intake and exhaust valves are open simultaneously. This occurs near TDC of the exhaust stroke.
---
### **How Far Out of Sync Would Cause All Valves to Be Open?**
For all cylinders to have at least one valve open, the camshafts would need to be misaligned enough to cause:
- Intake valves to remain open during the compression stroke, **or**
- Exhaust valves to remain open during the compression stroke.
This would require the camshafts to be out of sync by a significant number of degrees. Here's an estimate:
1. **Typical Valve Timing Range**:
- On the Ford 3.5L EcoBoost, the intake valves typically open **10–20 degrees before TDC** on the exhaust stroke and close **30–50 degrees after BDC** on the intake stroke.
- The exhaust valves typically open **40–60 degrees before BDC** on the power stroke and close **10–20 degrees after TDC** on the exhaust stroke.
2. **Critical Misalignment**:
- If the camshafts are misaligned by **90 degrees or more** (crankshaft degrees), it could cause valves to remain open during the compression stroke.
- For example:
- If the intake camshaft is **90 degrees retarded**, the intake valves may still be open during the compression stroke.
- If the exhaust camshaft is **90 degrees advanced**, the exhaust valves may still be open during the compression stroke.
3. **Worst-Case Scenario**:
- If the camshafts are misaligned by **180 degrees** (crankshaft degrees), the valves would be completely out of phase with the pistons. This would likely result in **all cylinders having at least one valve open** during the compression stroke, causing a complete loss of compression.
---
### **Practical Example:**
- If the timing chain slips by **10–15 teeth** (depending on the sprocket size), it could cause the camshafts to be misaligned by **90–180 degrees** (crankshaft degrees).
- This level of misalignment would likely result in valves being held open during the compression stroke, leading to no compression in all cylinders.
---
### **Diagnosing the Misalignment:**
1. **Check Timing Marks**:
- Rotate the crankshaft to TDC for cylinder 1 (compression stroke).
- Inspect the timing marks on the camshafts. If they are misaligned by more than a few degrees, the timing chain has slipped.
2. **Measure Cam/Crank Correlation**:
- Use a scan tool to check the camshaft and crankshaft position sensor data. If the camshafts are out of sync by **90 degrees or more**, it indicates a severe timing issue.
3. **Compression Test**:
- Perform a compression test on all cylinders. If all cylinders have little to no compression, it suggests the camshafts are significantly out of sync.
---
### **Conclusion:**
The camshafts would need to be out of sync by **90–180 degrees (crankshaft degrees)** to cause all cylinders to have at least one valve open during the compression stroke. This level of misalignment would likely result from a severe timing chain slip or failure. To confirm, inspect the timing marks, check cam/crank correlation, and perform a compression test. If the timing chain has slipped this far, you may also need to check for bent valves or other internal damage.
But my intrest is, can a chain be off enough to hold all cylinders in a state of no compression.
I found this to be very very interesting. This is from that new DeepSeek AI. I'm curious to see if anyone believes this.
If I'm off that far I can't believe the pistons didn't hit the valves during the chain slippage journey.
DEEPSEEK REPLY...
To determine how far the camshafts need to be out of sync (in degrees) to cause **all cylinders to have at least one valve open** on a Ford 3.5L EcoBoost engine, we need to consider the engine's valve timing and the relationship between the crankshaft and camshafts.
---
### **Key Concepts:**
1. **Crankshaft Rotation**:
- The crankshaft completes **720 degrees** of rotation for a full engine cycle (intake, compression, power, exhaust).
- The camshafts rotate **360 degrees** during the same cycle (since they turn at half the speed of the crankshaft).
2. **Valve Timing**:
- The intake and exhaust valves open and close at specific points in the crankshaft's rotation.
- The exact timing depends on the engine's design, but typically:
- **Intake valves** open slightly before Top Dead Center (TDC) on the exhaust stroke and close after Bottom Dead Center (BDC) on the intake stroke.
- **Exhaust valves** open before BDC on the power stroke and close after TDC on the exhaust stroke.
3. **Overlap Period**:
- There is a brief period called **valve overlap** where both the intake and exhaust valves are open simultaneously. This occurs near TDC of the exhaust stroke.
---
### **How Far Out of Sync Would Cause All Valves to Be Open?**
For all cylinders to have at least one valve open, the camshafts would need to be misaligned enough to cause:
- Intake valves to remain open during the compression stroke, **or**
- Exhaust valves to remain open during the compression stroke.
This would require the camshafts to be out of sync by a significant number of degrees. Here's an estimate:
1. **Typical Valve Timing Range**:
- On the Ford 3.5L EcoBoost, the intake valves typically open **10–20 degrees before TDC** on the exhaust stroke and close **30–50 degrees after BDC** on the intake stroke.
- The exhaust valves typically open **40–60 degrees before BDC** on the power stroke and close **10–20 degrees after TDC** on the exhaust stroke.
2. **Critical Misalignment**:
- If the camshafts are misaligned by **90 degrees or more** (crankshaft degrees), it could cause valves to remain open during the compression stroke.
- For example:
- If the intake camshaft is **90 degrees retarded**, the intake valves may still be open during the compression stroke.
- If the exhaust camshaft is **90 degrees advanced**, the exhaust valves may still be open during the compression stroke.
3. **Worst-Case Scenario**:
- If the camshafts are misaligned by **180 degrees** (crankshaft degrees), the valves would be completely out of phase with the pistons. This would likely result in **all cylinders having at least one valve open** during the compression stroke, causing a complete loss of compression.
---
### **Practical Example:**
- If the timing chain slips by **10–15 teeth** (depending on the sprocket size), it could cause the camshafts to be misaligned by **90–180 degrees** (crankshaft degrees).
- This level of misalignment would likely result in valves being held open during the compression stroke, leading to no compression in all cylinders.
---
### **Diagnosing the Misalignment:**
1. **Check Timing Marks**:
- Rotate the crankshaft to TDC for cylinder 1 (compression stroke).
- Inspect the timing marks on the camshafts. If they are misaligned by more than a few degrees, the timing chain has slipped.
2. **Measure Cam/Crank Correlation**:
- Use a scan tool to check the camshaft and crankshaft position sensor data. If the camshafts are out of sync by **90 degrees or more**, it indicates a severe timing issue.
3. **Compression Test**:
- Perform a compression test on all cylinders. If all cylinders have little to no compression, it suggests the camshafts are significantly out of sync.
---
### **Conclusion:**
The camshafts would need to be out of sync by **90–180 degrees (crankshaft degrees)** to cause all cylinders to have at least one valve open during the compression stroke. This level of misalignment would likely result from a severe timing chain slip or failure. To confirm, inspect the timing marks, check cam/crank correlation, and perform a compression test. If the timing chain has slipped this far, you may also need to check for bent valves or other internal damage.
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FaaWrenchBndr
Well-known member
- First Name
- Greg
- Joined
- Jun 23, 2024
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- ‘24 XLT Powerboost
- Occupation
- Semi retired aircraft mechanic
yes, this one is crazy for sure
v8440
Well-known member
Ask it about stroker kits for a buick 350 and see what it says. Microsoft copilot gets that wrong, or did last time I checked. It referred you to butler performance, which specializes in PONTIAC engines. They have stroker kits for a pontiac 350. They don't have them for a buick 350. Here's the trick-neither does anyone else, either. The buick's stroke is so long that the big end of the connecting rod is close to hitting the camshaft from the factory. There's no room to add stroke without drastic measures such as turning the stock rod journals down and offset grinding the crank, and having rods made with a smaller big end. This is the kind of stuff garden variety ai chatbots seem to get wrong.
HammaMan
Well-known member
OAI started by 'stealing' all of the data on the internet it could with zero respect to the copyright holders. In fact one of the biggest problems for the past year is that all of the models have consumed all of the internet and the models need even more input. As such they're having to generate artificial inputs to grow them now. Thieves really don't have any agency to claim loss over ill gotten gains.
Spiffy
Well-known member
- Thread starter
- #44
Can you imagine. AI running for president of the world in 10 years? It will be judge, jury and executioner. And if you piss it off all our cars shut down.
This last couple years the growth of AI is scary. How would we punish AI if it decided to kill someone? Put it in jail? Could someone us it to crash planes?
Enough about that for me. I just need to fix my truck.
I can't wait to get my hands on my cylinder scope.
This last couple years the growth of AI is scary. How would we punish AI if it decided to kill someone? Put it in jail? Could someone us it to crash planes?
Enough about that for me. I just need to fix my truck.
I can't wait to get my hands on my cylinder scope.
Captain Dirty Beard
Well-known member
Just depends on which way the chain jumped or skip relative to rotation. If the chain jumps in an advanced position, the intake valves would still be open on the compression stroke, and so the pistons would hit the intake valves. If the chain jumped in a retarded position, the exhaust valves would still be open and damage those
You probably would not hear any sound. The valves and stems are tiny and insignificant relative the entire rotating assembly. Once the stem bends, it has been "self clearanced" and no longer hits the piston. Just depends on how far out of time it was, and how much interference there was.
You might be able to snake your scope in through the oil fill hole and down the timing cover to look at the crank sprocket. Just depends on how much room there is, and how slim the scope is
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