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| One Cylinder Low Compression...Your Diagnosis? https://slantsix.org/forum/viewtopic.php?t=3474 |
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| Author: | Mitch [ Sun Apr 14, 2002 3:39 pm ] |
| Post subject: | One Cylinder Low Compression...Your Diagnosis? |
I'd like to tap the knowledge on this board. My 1980 Aspen 1bbl slant has low compression in #5. 100-110 compared to about 140 in the other cylinders. The engine shakes some at idle and intermittantly 'puts' through the exhaust Pulling #5 spark plug wire produces only a moderate rpm drop at idle. The engine burns no oil and did not seem to loose much if any power on the highway. The engine pulls about 19 in of vacuum at idle. All the plugs show normal. What happened? I recently went through a bad tank of gas. The engine moderately pinged on the highway. My guess is i have a bad exhaust valve. How common is exhaust valve recession on these engines? What would be your course of action? I think I will pull the valve cover to check the valve adjustment. Thanks Mitch m5black@aol.com |
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| Author: | wolverine [ Sun Apr 14, 2002 6:49 pm ] |
| Post subject: | Re: One Cylinder Low Compression...Your Diagnosis? |
Quote:
: I'd like to tap the knowledge on this board. My : 1980 Aspen 1bbl slant has low compression in : #5. 100-110 compared to about 140 in the : other cylinders. The engine shakes some at : idle and intermittantly 'puts' through the : exhaust Pulling #5 spark plug wire produces : only a moderate rpm drop at idle. The engine : burns no oil and did not seem to loose much : if any power on the highway. The engine : pulls about 19 in of vacuum at idle. All the : plugs show normal. What happened? : : I recently went through a bad tank of gas. The : engine moderately pinged on the highway. My : guess is i have a bad exhaust valve. How : common is exhaust valve recession on these : engines? What would be your course of : action? I think I will pull the valve cover : to check the valve adjustment. : : Thanks : : Mitch go to slantsix.com and read my post "problems-help" by wolverine. i had some similar symptoms and might help you out problems-help dodgecrazy@aol.com |
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| Author: | Doctor Dodge (Doug Dutra) [ Sun Apr 14, 2002 10:17 pm ] |
| Post subject: | Re: One Cylinder Low Compression...Your Diagnosis? |
Quote:
: I'd like to tap the knowledge on this board. My : 1980 Aspen 1bbl slant has low compression in : #5. 100-110 compared to about 140 in the : other cylinders. The engine shakes some at : idle and intermittantly 'puts' through the : exhaust Pulling #5 spark plug wire produces : only a moderate rpm drop at idle. The engine : burns no oil and did not seem to loose much : if any power on the highway. The engine : pulls about 19 in of vacuum at idle. All the : plugs show normal. What happened? : : I recently went through a bad tank of gas. The : engine moderately pinged on the highway. My : guess is i have a bad exhaust valve. How : common is exhaust valve recession on these : engines? What would be your course of : action? I think I will pull the valve cover : to check the valve adjustment. In 1980 the SL6 got hydraulic lifters so peek into the oil fill hole to see if there are adjusters screws, if not, it's a hydraulic lifter engine and pulling the valve cover won't be worth the gasket needed to put it back on. (If it is a mechanical lifter engine, the by all means, readjust the valves, that will most likly help) As for seat recession, it is a problem, especially with the early engines. Even the late engines with the factory induction hardened seats can still eat through the thin layer of harness and recess the seat. DD |
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| Author: | Mitch [ Mon Apr 15, 2002 10:37 am ] |
| Post subject: | Re: One Cylinder Low Compression...Your Diagnosis? |
Thanks. While you had a 'similar' problem, mine is a bit different. I thought I might have had crossfire, so I checked my cap and rotor and changes my wires. Still the same. The key is low compression in the #5 cylinder. I am going to go through the valve adjustment tomorrow. Maybe I'll find something. Mitch Quote:
: : go to slantsix.com and read my post : "problems-help" by wolverine. i : had some similar symptoms and might help you : out m5black@aol.com |
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| Author: | Mitch [ Mon Apr 15, 2002 10:44 am ] |
| Post subject: | Re: One Cylinder Low Compression...Your Diagnosis? |
Thanks. I have a solid cam. I will check the valve adjustment. That should give me more clues. I adjusted the valves twice: once at 30K and last at about 50K. I now have 110K. The second adjustment showed almost no change. Of course, I might have a bad valve with no seat recession. Too bad. The car otherwise runs great. I'll share my findings. Mitch Quote:
: : In 1980 the SL6 got hydraulic lifters so peek : into the oil fill hole to see if there are : adjusters screws, if not, it's a hydraulic : lifter engine and pulling the valve cover : won't be worth the gasket needed to put it : back on. : (If it is a mechanical lifter engine, the by : all means, readjust the valves, that will : most likly help) : As for seat recession, it is a problem, : especially with the early engines. Even the : late engines with the factory induction : hardened seats can still eat through the : thin layer of harness and recess the seat. : DD m5black@aol.com |
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