Cracked rocker arms

476 Views 9 Replies 5 Participants Last post by Lou O., 4 d ago

Elizstoy

Discussion Starter · 8 d ago

Ok I was sitting at a stop light and my 07 Solstice GXP died and wouldn't restart I got a P0017 and a P0336 codes pending. So I changed the crankshaft position sensor no help both VVT'S still no help won't start. Someone said timing chain when I pulled off the valve cover timing chain was ok no slack then I saw these all 8 on the driver's side (intake correct?) We're broken. Now what would cause this to happen all the lash adjuster's can come out none stuck. So off to AutoZone bought the Melling MR-1340 $9.99 each now I saw on Amazon these by EPChunMi both rockers and lifters both $84.99 has anyone used these. When I saw the rockers the way they snapped at the light I heard no bang, crack nothing car just died. Any advise is great fully accepted on why this would of happened and also what else I should be looking for. Thanks in advance

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JohnWR

· #2 · 8 d ago

I would be concerned about the engine jumping time and causing contact between the intake valves and the pistons.

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agent008

· #3 · 8 d ago

Whoa that is a failure mode I've never seen before. I can't say what might have caused but agree with John that you should remove the head and look for signs of valve to piston contact, and check for bent valves, etc.

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Elizstoy

Discussion Starter · #4 · 6 d ago

Thank you for your advise I will that again thank you for your time and advise

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Lou O.

· #5 · 6 d ago

Those finger roller followers and stationary hydraulic lash adjusters should never go bad/fail. There is not that much stress on them from the valve spring or action of the VVT. I've never seen this failure on durability engines ran at GM in the past. Almost makes me wonder if it might be a manufacturing spill. Something created a nasty stress riser or its a material issue. Of course being this old, gm will not care to even look at the parts. Eaton made these back in the day, as I recall. They were not made inhouse by gm. Sorry this happened to you, and you may never know why. I do know they are not unique to exh or intake, they are all the same part number. Why only intakes failed....good question. How many miles on your car and do you use good quality full synthetic oil?? You should be able to cycle the motor over by hand with the valve cover off to witness valve train action and any type of anomaly with the valves/springs.

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Elizstoy

Discussion Starter · #6 · 6 d ago

Lou O. said:
Those finger roller followers and stationary hydraulic lash adjusters should never go bad/fail. There is not that much stress on them from the valve spring or action of the VVT. I've never seen this failure on durability engines ran at GM in the past. Almost makes me wonder if it might be a manufacturing spill. Something created a nasty stress riser or its a material issue. Of course being this old, gm will not care to even look at the parts. Eaton made these back in the day, as I recall. They were not made inhouse by gm. Sorry this happened to you, and you may never know why. I do know they are not unique to exh or intake, they are all the same part number. Why only intakes failed....good question. How many miles on your car and do you use good quality full synthetic oil?? You should be able to cycle the motor over by hand with the valve cover off to witness valve train action and any type of anomaly with the valves/springs.

Thanks for the reply I have had the car for 3 years always did my oil change changed my plugs about every 4 months and it just passed smog here in Cali in February. Thank you for the advice well taken

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Lou O.

· #7 · 6 d ago

@Elizstoy How did the cam lobes look? Is this a high mileage motor?

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OnaWingandaPrayer

· #8 · 5 d ago

If it did not jump time on the chain , I would suspect a problem with the cam/phaser changing the cam timing to far . It's really hard to think all 8 intakes failed from manufacture problem ( problem with the rockers) . Impossible odds for them all to fail unless there is a mechanical fail .

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Lou O.

· #9 · 5 d ago (Edited)

OnaWingandaPrayer said:
If it did not jump time on the chain , I would suspect a problem with the cam/phaser changing the cam timing to far . It's really hard to think all 8 intakes failed from manufacture problem ( problem with the rockers) . Impossible odds for them all to fail unless there is a mechanical fail .

I agree, but there is an internal mechanical stop in the cam phaser to prevent this from happening. If the phaser solenoid went into some sort of dithering mode?...but the OP said he was at idle. If the SHLA seat is too shallow it would permit this failure mode. If this occurs due to incorrect machining (it happens) the 'lash' in the lifter will bottom out making a 'solid lifter' and thus create a hard stop at max cam lift. Not a good scenario. I personally reworked 1200 engines at Flint Engine South, the 4.2 L inline six due to this exact issue. A set up person could not do basic math during a tool change and went shallow on the SHLA seat. Cold Motoring Test caught the condition.....

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Lou O.

· #10 · 4 d ago

Oh...if its a shallow SHLA issue the only way to correct the problem is remove the head and machine the base / pocket that the SHLA sits in. Not an easy job. I personally would get another head, used, if this really the issue. You can measure the depth of the SHLA yourself with a caliper that has a depth gauge built in. Use the exhaust side as your guide for a baseline. Measure from the bottom of the bore to the top chamfer of the bore. GM did not machine the face of the SHLA pocket, which makes it harder to measure; it's an as cast surface.

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