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454 valve train noise $$?

L

lenoah

New member
Getting ready to head for Catalina and port engine starts making a LOUD tapping noise. Mechanic comes down, compression checks good, 200 hrs on the engine. Pull the valve cover and rockers and on valve looks like it has receeded into the keeper. Keeper is still there but the top of the valve stem is almost flush with the keeper unlike the others where the valve stem sticks up an 1/8" or so.

Summer was late here so mechanic is booked and can't come back for a few days. So we're trying to find out if any one has seen this before. If we can get a spring compresser on there what are the chances that the keepers are distorted vs valve stem damage. Keepers are relatively easy. Valve problem means the head has to come off.

Or could it be the washer (not the right terminology) that sits on top of the valve spring?

ANyone seen this? Ideas?
 
I am not aware of the year of engine you may have so I will base this comment on what I had with my own. Two years ago on the travelift during spring launch, we atarted the engines ready to go into our slip when the loud noise, irregular idle and 800 max rpm at full throttle developed.

Our problem dictated a complete valve job. Sounds like you are describing possible damage to the valve stem retainer groove on the valve stem causing the retainers to slip or recess into the valve spring cap? If this is the case I see no other way around it other than to remove the head and replace the valve.

You probably can't see much beyond the cap due to the valve spring and sheild assembly. Nothing else supports the valve upward lift and the noise is due to the large gap between the rocker arm and the valve stem end
 
I think you will find those keepers are pretty tough and not likely to distort. Same for their mating surface on the stem.

I'd suggest taking a couple more measurements so you can figure out exactly what has changed. I'd be more inclined to think the rocker and valve stem tip have eroded each.
 
Thanks for the ideas guys. Yep, we understand that the gap is causing the noise. That is how we tracked it down. We'll check the rocker and valve stem tip for abnormal wear.
Obviously we wouold like to find that it is something that doesn'trequire pulling the head. This is a OEM replacement engine that was located in a warehouse. Probably mid-90's vintage.
We were encouraged that compression was good.
 
Yep, what Mark said. One valve stem and corresponding rocker are eroded. What causes that? Now we're wondering if we should open up the other side to check those valves too.
 
My best guess? Water getting into the exhaust port, rusting the valve to the head, which caused excessive load on the valve train. Those 454s are famous for sucking in water.

Jeff
 
lenoah said:
Yep, what Mark said. One valve stem and corresponding rocker are eroded. What causes that? Now we're wondering if we should open up the other side to check those valves too.
Click to expand...

Eroded? or worn? If worn, that can be caused by a loosened valve adjustment nut (best case) to a worn cam lobe (worst case). Once the valve tip starts to go, it may be thru the hardened area and further wear is fast. I think that head is coming off for a new valve.
 
Like Dave said, once thru the hardened surfaces, the gap gets big really fast if you keep running the engine.

I'd measure the cam before taking the heads off for a visit to the machine shop.

Another item to add to DD's possible causes (best case end) is the "collapsed" lifter.
 
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