| Bad Valve Lifter? [message #211276] |
Sun, 16 June 2013 14:12  |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
Karma: 0
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Senior Member |
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78 403 with 61,000 miles.
I've had an engine noise developing over the last 1,000 - 1,500 miles that I think I have finally determined to be a bad valve lifter. The noise is somewhat intermittent at idle although it's most of the time now. It usually diminishes or disappears as the engine speed increases although with the engine cover off I can now here it up to 1500 rpm or so. It's more of a tap than a knock although it's become a pretty substantial "tap".
I put a timing light on it and it appears the tap sounds every time the light flashes which indicates a valve-related problem (1/2 engine speed), right? It sounds too "sharp" to me to be an exhaust leak (I have headers) and I don't hear anything through a hose near the gasket and don't feel anything.
I put a HF stethoscope on it and I hear it most in the drivers side head although I can't pin it down to a cylinder. I haven't pulled the valve cover yet or started pulling spark plug wires.
Questions:
- Is there anything else I should do to firm up my diagnosis before I dig into the engine?
- How urgent is it to fix this? Can I drive it a few hundred miles without much risk of creating a much bigger problem?
- Is this something I can do myself? I actually did this once, over 40 years ago on a 1968 El Camino 307. As I recall the results were less than stellar, as in I couldn't get the engine to start once I got it back together. In retrospect, I think I probably put the distributor back in wrong but I'm not sure I figured that out at the time.
- If I do it myself what kinds of problems am I like to encounter? It doesn't look like the distributor has to come out although I think I would probably pay more attention to how it came out this time and probably get it back right. Breaking bolts I can probably deal with. Getting the intake manifold properly seated and sealed seems less critical with the OEM manifold than with the aluminum upgrade. I would probably use Jim K's "block-off plate with gasket" to block off the cross-over while I've got it apart.
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: Bad Valve Lifter? [message #211281 is a reply to message #211276] |
Sun, 16 June 2013 15:12  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Pull the drives valve cover and see if any are slack. Try stethoscope at idle and you should find it. A tool like short section of heater hose can put pressure on the suspect rocker. If its a worn or scored rocker or bent pushrod it's an easy fix from above. Watch for bent push rod as they spin, or roll in your fingers to inspect when cool. . Lifter means pulling intake. Lifter could have dirt causing leak down or a worn foot exceeding the hydraulic tolerance--- which then puts the cam health in question. If the cam is ok use real GM lifter and assembly lube and break in protocol to mate the lifter to cam surface. Hope for a topside bolt on fix .
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Bad Valve Lifter? [message #211340 is a reply to message #211276] |
Mon, 17 June 2013 07:48 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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Before you take anything apart, try using a 3-4' section of vinyl (drip
irrigation or garden hose) tubing and with one end in or close to your ear,
move the other end along the seam where the exhaust manifold meets the cyl
head. Exhaust leaks often sound quite close to lifter noise and diminish
as rpm rises and the engine heats up.
Steve F
On Sun, Jun 16, 2013 at 12:12 PM, Darryl Meyers <hospacctg@att.net> wrote:
>
>
> 78 403 with 61,000 miles.
>
> I've had an engine noise developing over the last 1,000 - 1,500 miles that
> I think I have finally determined to be a bad valve lifter. The noise is
> somewhat intermittent at idle although it's most of the time now. It
> usually diminishes or disappears as the engine speed increases although
> with the engine cover off I can now here it up to 1500 rpm or so. It's
> more of a tap than a knock although it's become a pretty substantial "tap".
>
> I put a timing light on it and it appears the tap sounds every time the
> light flashes which indicates a valve-related problem (1/2 engine speed),
> right? It sounds too "sharp" to me to be an exhaust leak (I have headers)
> and I don't hear anything through a hose near the gasket and don't feel
> anything.
>
> I put a HF stethoscope on it and I hear it most in the drivers side head
> although I can't pin it down to a cylinder. I haven't pulled the valve
> cover yet or started pulling spark plug wires.
>
> Questions:
>
> - Is there anything else I should do to firm up my diagnosis before I dig
> into the engine?
>
> - How urgent is it to fix this? Can I drive it a few hundred miles
> without much risk of creating a much bigger problem?
>
> - Is this something I can do myself? I actually did this once, over 40
> years ago on a 1968 El Camino 307. As I recall the results were less than
> stellar, as in I couldn't get the engine to start once I got it back
> together. In retrospect, I think I probably put the distributor back in
> wrong but I'm not sure I figured that out at the time.
>
> - If I do it myself what kinds of problems am I like to encounter? It
> doesn't look like the distributor has to come out although I think I would
> probably pay more attention to how it came out this time and probably get
> it back right. Breaking bolts I can probably deal with. Getting the
> intake manifold properly seated and sealed seems less critical with the OEM
> manifold than with the aluminum upgrade. I would probably use Jim K's
> "block-off plate with gasket" to block off the cross-over while I've got it
> apart.
> --
> Darryl Meyers
>
> 1978 Eleganza II
>
> El Dorado Hills, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Take care,
Steve
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| Re: [GMCnet] Bad Valve Lifter? [message #211348 is a reply to message #211276] |
Mon, 17 June 2013 08:36 |
Ron77
Messages: 91
Registered: August 2012
Karma: 0
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Member |
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A gradual onset like you describe could also be caused by a cam lobe wearing down and reducing the lift, resulting in a gap between the cam lobe and the lifter. Checking the lift with a dial indicator would disclose this condition. If that is what it is, there would be metal in the oil, so sending a sample for analysis could be helpful.
Ron Johnson
On Jun 16, 2013, at 12:12 PM, Darryl Meyers <hospacctg@att.net> wrote:
>
>
> 78 403 with 61,000 miles.
>
> I've had an engine noise developing over the last 1,000 - 1,500 miles that I think I have finally determined to be a bad valve lifter. The noise is somewhat intermittent at idle although it's most of the time now. It usually diminishes or disappears as the engine speed increases although with the engine cover off I can now here it up to 1500 rpm or so. It's more of a tap than a knock although it's become a pretty substantial "tap".
>
> I put a timing light on it and it appears the tap sounds every time the light flashes which indicates a valve-related problem (1/2 engine speed), right? It sounds too "sharp" to me to be an exhaust leak (I have headers) and I don't hear anything through a hose near the gasket and don't feel anything.
>
> I put a HF stethoscope on it and I hear it most in the drivers side head although I can't pin it down to a cylinder. I haven't pulled the valve cover yet or started pulling spark plug wires.
>
> Questions:
>
> - Is there anything else I should do to firm up my diagnosis before I dig into the engine?
>
> - How urgent is it to fix this? Can I drive it a few hundred miles without much risk of creating a much bigger problem?
>
> - Is this something I can do myself? I actually did this once, over 40 years ago on a 1968 El Camino 307. As I recall the results were less than stellar, as in I couldn't get the engine to start once I got it back together. In retrospect, I think I probably put the distributor back in wrong but I'm not sure I figured that out at the time.
>
> - If I do it myself what kinds of problems am I like to encounter? It doesn't look like the distributor has to come out although I think I would probably pay more attention to how it came out this time and probably get it back right. Breaking bolts I can probably deal with. Getting the intake manifold properly seated and sealed seems less critical with the OEM manifold than with the aluminum upgrade. I would probably use Jim K's "block-off plate with gasket" to block off the cross-over while I've got it apart.
> --
> Darryl Meyers
>
> 1978 Eleganza II
>
> El Dorado Hills, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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