So I was getting ready last night to go out for my VERY FIRST cruise in the Olds. The engine was idling while I was getting everything ready. All of a sudden I noticed it didn't feel right and then started hearing a really loud metalic ping sound coming from the intake area. It got MUCH louder when I removed the air cleaner so the noise is coming out of the carb.

I have yet to do a compression test or pull off the valve covers as today is my aniversary so I just have to put it off!!! LOL...... Could this type of noise be caused by broken valve springs or sticking vavles??? It sounds to me like the valve is being slammed shut by the piston.

 

There coud be many things but after sitting it could be a collapsed lifter or stuck valve. The best thing to do is pull the valve covers and look for anything broken, bent pushrod, or a loose rocker. If nothing is seen run engine and listen and look. Hopefullyfind something. As for the noise coming out of the carb that could mean an intake valve is stuck open but hopefully the noise just seems louder with the air breather off. Let us know what you find, with that engine!

 

Considering you said you had it running for a while and then you heard the noise after it had idled for a time in your Driveway, a stuck Valve would usually only happen if you had revved the motor and one might get stuck.

I would suggest that this would be an opportune time for a Valve Spring to break as you said, after all it was only Idling.

Get out your Mag Lite and look closely at the angle of your Springs before you go to far with this project as it could save time in the process of elimination of your troubles.

 

If you don't have a mechanic stethoscope, use a long screwdriver and put your ear up to it while moving around the engine. That may help to pinpoint where the problem is.

 

Happy anniversary.
The car is jealous, and it is lacking your attention.
Now we know why men give cars women's names.

Do not speculate, get the valve covers off, and get a compression gauge on it PRONTO!
Hoping it is not too bad a fix.
We will wait for your response.
Jim

 

LOL yeah thats what my friends said. Maybe its the "Christine" curse!!!! LOL

So with a sore back and all today I decided to at least pull off the valve covers. It would have been bothering me all day unless I did. I am very glad I did because I found a broken rocker arm on the passanger side head.

I would prefer to replace all the rockers now. Any recommendations for replacement rockers???? Just stock replcements nothing fancy.

 

Question is why did it break? Maybe coincidental maybe still some sort of problem. Check things out.

 

Was it the stamped steel rocker or the aluminum bridge that broke?

 

It was the stamped steel rocker itself. It broke right under the pivot. From what I have been reading its not totally uncommon for the factory rockers to crack or break.

 

Hi Craig
Can you see if the crack is old, somthing that had been forming gradually over time from stress or a fresh crack like it gave all at once? I've seen a couple broken bridges but the only damaged stamped steel piece I've seen was on a boat that had been over-revved and the pushrod went through the cup on the stamped steel piece. I'm not an expert by any means, but I agree with Oldsmaniac. Please take the time to make sure nothing else is wrong that may have contributed to the failure. John

 

Everything seems to be fine with the valve & spring. I will be pulling the intake to replace it so I will inspect the lifters at that time.

Here are some pics of what I found.

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Here is the exhaust rocker from the same cylinder.

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Here are some close ups. I am pretty sure it was failure due to age. You can see quite a bit of cracking around where the bolt goes through. It looks like the main break actually started at one of these cracks.

DSCN1666.jpg

DSCN1670.jpg

 

that's a strange waer patteren where the rocker rides on the valve.

 

Wow! That was quite a break! I guess I'll look a little more closely at old rockers I consider re-using. John

 

I have a feeling someone installed a bunch of mix matched used rockers at some point. There is a huge difference in appearance even between the two rockers on the same cylinder. The exhaust is extremely shiny while the broken intake rocker is very dull & pitted. I have dark bridges & shiny aluminium bridges. Seems like too much of a mismash to have all been installed new at the same time.

 

Make SURE that the pushrod is not blocked, and moving oil through it. A dark bridge may mean it has been running uber hot, just a matter of time.
Run a piece of wire through it, blow it out with compressed air/ carb cleaner, and make it come out clean.
Check valve stem tip, and LIGHTLY polish tip if you can. Try not to remove much material, that will affect stem tip height. If valve tip is ground up, I would recommend a new valve.....eventually.
I am glad it did not twist, and try to compress the retainer without the valve...THAT would be a headache, and a heartache.
Jim

 

You really got some unusual Stress cracks, ya better take them all down and see what the rest of them look like. Of course a guy such as yourself will do that anyway. Best of luck and hope you get the problem straightened out real soon....

 

looks like an oiling issue with those shiny scratches

 

I will be inspecting all the lifters & pushrods shortly and repalcing anything that even hints at failure.

These are the rockers I think I will be going with. http://www.summitracing.com/parts/CCA-1242-16/ One thing I have noticed is most sites say these rockers are ok for 1967+ 425 engines but not before. I wasn't aware there was a difference in the valvetrain in 425's. I knew there was a difference 425-455 but not between 425's??

 

valvetrain angle was different 39 degrees and 45 degrees but i dont think those rockers were different because you can swap those heads just by drilling out the pushrod opening. also i dont think 425's were made after 67