Rocker arm failure on track
11-11-2018, 03:20 PM
#31
Registered User
this just happened to me. Ap1 with 86,044 miles. Exhaust valve dropped and an intake valve stem snapped at the top. I'd upload the photos but dont know how to do that lol. Mine may look even worse! Ap2 retainers installed 5 years ago. Rockers are all fine.
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RedCelica (11-14-2018)
11-11-2018, 10:14 PM
#33
Registered User
If this was rocker arm failure wouldn't the valve just remain closed and leave you with a 3 cylinder car?
The piston must have hit the valve and broken the rocker. It is common on many engines for the rocker or cam even to get broken.
The question is what was floating round in the combustion chamber as every part of the head, piston and even the top part of the bore has damage.
Valve float at an earlier part of the lap? Failure a little later enough time for parts to bounce around the cylinder
Grind off the end of the damaged plug and inspect the electrode insulator sure it will be broken but is it complete?
How do you adjust your plug gaps?
Time for a mega rebuild
Have fun
The piston must have hit the valve and broken the rocker. It is common on many engines for the rocker or cam even to get broken.
The question is what was floating round in the combustion chamber as every part of the head, piston and even the top part of the bore has damage.
Valve float at an earlier part of the lap? Failure a little later enough time for parts to bounce around the cylinder
Grind off the end of the damaged plug and inspect the electrode insulator sure it will be broken but is it complete?
How do you adjust your plug gaps?
Time for a mega rebuild
Have fun
11-11-2018, 11:47 PM
#34
Registered User
So this is the inlet side which had just been upgraded to ap2 retainers? Dropped valve then. Can you post pics of inlet valve caps? are the retainers in place as the exhaust ones are?
11-12-2018, 12:19 PM
#36
11-12-2018, 01:26 PM
#37
A definition:
Originally Posted by https://www.carsdirect.com/car-repair/what-to-do-if-you-dropped-an-engine-valve
In car engines, an engine valve that is said to have dropped refers to a valve in the cylinder head of the engine that has usually broken off at the stem that connects the valve to the rod. After the valve breaks off, the valve seat usually rattles around inside the cylinder and can cause significant and expensive damage to the cylinder head of the vehicle.
11-12-2018, 03:13 PM
#39
Registered User
1 inlet and 1 exhaust
There is no pics yet of the inlet valve retainers
I think pics of inlet will show dropped valve
This is the valve that had been updated to ap2 recently
11-12-2018, 03:35 PM
#40
In many NA cars, the valve stem is small diameter to limit its intrusion on the airflow. Many valves come with the portion near the head narrowed for this. Ferrea calls it "Super Flo" and is on their F20/F22 intakes valves. While not on S2000 valves, some valves have hollow valve stems, and for some engines, the hollow exhaust valves are sodium cooled. That is increasingly common for OEM turbos.
The valve heads get very hot, especially the exhaust. Cooling takes place through the valve seats and valve guides. The intake is also cooled by the incoming mixture. The sodium fill transfers heat from the head to valve guide. Beryllium seats have higher thermal conductivity. Coatings can reduce heat transfer to the valve.
Aggressive camshafts put more of a load on the head. In addition to more spring pressure on the seat, the landing is often more abrupt. When it lands there is are still multiple cycles of tension because of oscillations in the valve springs. Those oscillations are why I am enamored with conical (conical, not beehive) valve springs, although I don't have any empirical data that they make a difference and are generally not available for sport-compact applications. CompCams has them for SB Chevy applications, GSC has them from 2JZ-GTE engines. All performance VTEC applications are fairly aggressive, although aftermarket cams, especially VTEC-killers, more so. On NA engines especially, intake closing can be quick; it is a trade-off between compression and airflow.
Against that Honda designed this to meet street use with relatively high OEM redlines, so this failure is relatively rare. I had it happen to me on a small-block Chevy; the valve head destroyed the piston sending the rod through the side of the block. The car spun in the brown oil/water mix that spewed out of the block. Everything had shrapnel damage. The intake, exhaust, oil pan, and water pump were salvaged.
If I have read this thread correctly, the broken rocker was on the cylinder that dropped a valve. If so, I'm guessing one of the intakes became jammed shut causing the cam the break the rocker.
The valve heads get very hot, especially the exhaust. Cooling takes place through the valve seats and valve guides. The intake is also cooled by the incoming mixture. The sodium fill transfers heat from the head to valve guide. Beryllium seats have higher thermal conductivity. Coatings can reduce heat transfer to the valve.
Aggressive camshafts put more of a load on the head. In addition to more spring pressure on the seat, the landing is often more abrupt. When it lands there is are still multiple cycles of tension because of oscillations in the valve springs. Those oscillations are why I am enamored with conical (conical, not beehive) valve springs, although I don't have any empirical data that they make a difference and are generally not available for sport-compact applications. CompCams has them for SB Chevy applications, GSC has them from 2JZ-GTE engines. All performance VTEC applications are fairly aggressive, although aftermarket cams, especially VTEC-killers, more so. On NA engines especially, intake closing can be quick; it is a trade-off between compression and airflow.
Against that Honda designed this to meet street use with relatively high OEM redlines, so this failure is relatively rare. I had it happen to me on a small-block Chevy; the valve head destroyed the piston sending the rod through the side of the block. The car spun in the brown oil/water mix that spewed out of the block. Everything had shrapnel damage. The intake, exhaust, oil pan, and water pump were salvaged.
If I have read this thread correctly, the broken rocker was on the cylinder that dropped a valve. If so, I'm guessing one of the intakes became jammed shut causing the cam the break the rocker.