 Compression numbers, how bummed out should I be?, Update: All's well after valve adjustment |
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| PDXMike |
 Jan 7 2012, 06:54 PM
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#1
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Slowly Learning  Group: Members Posts: 111 Joined: 20-December 10 From: Portland, OR Member No.: 12,501 Region Association: Pacific Northwest  |
I did a compression test and here are the results:
1 = 90psi 2 = 130psi 3 = 122psi 4 = 125psi I did cylinder #1 twice, just to be sure. It was consistent at 90. I wasn't experiencing any problems, I was just curious about the condition of the engine as I don't know any history on the car. #1 obviously is not up to snuff, but how bad is it? Don't venture far from home bad? or Rebuilding might give me some more horsepower bad? Thanks, Mike |
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| JamesM |
Jan 7 2012, 06:56 PM
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#2
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Senior Member Group: Members Posts: 1,900 Joined: 6-April 06 From: Kearns, UT Member No.: 5,834 Region Association: Intermountain Region |
When was the last time you adjusted the valves?
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| mrholland2 |
Jan 7 2012, 07:05 PM
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#3
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Senior Member Group: Members Posts: 750 Joined: 7-September 11 From: Santa Maria,CA Member No.: 13,531 Region Association: Central California |
QUOTE(JamesM @ Jan 7 2012, 04:56 PM)  When was the last time you adjusted the valves? (IMG:style_emoticons/default/agree.gif) I'm not "Mr. Mechanic", but that would seem to be a logical starting point. (And relatively inexpensive) |
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| aircooledtechguy |
Jan 7 2012, 07:56 PM
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#4
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The Aircooledtech Guy Group: Members Posts: 1,966 Joined: 8-November 08 From: Anacortes, WA Member No.: 9,730 Region Association: Pacific Northwest |
QUOTE(JamesM @ Jan 7 2012, 04:56 PM) When was the last time you adjusted the valves? (IMG:style_emoticons/default/agree.gif) That should be the first thing you do and then re-test. This page features a beetle engine, but the procedure is EXACTLY the same: http://www.aircooledtech.com/valve_adjust/ A couple other things to keep in mind about compression testing: 1. The motor should be warm for accurate readings (they will be lower cold) 2. You should have the throttle wide open when cranking (you will have low numbers if closed). |
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| euro911 |
Jan 7 2012, 08:16 PM
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#5
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,849 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California 
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My wife's 71 1.7L idled poorly (hunting - Hi/Low pulsing) when we first acquired it. I installed new vacuum lines, new points & condenser, plugs and cleaned the trigger points, but that still didn't help with the erratic idle.
When I did a compression check, #1 & #2 were OK at 125, but #3 was 110 and #4 was only 85. I found 3 & 4 were adjusted too tight (couldn't even get the feeler gauge in). After adjusting, 3 & 4's readings came up to 120 and the car no longer hunted for a stable idle speed. |
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| PDXMike |
Jan 7 2012, 08:25 PM
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#6
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Slowly Learning Group: Members Posts: 111 Joined: 20-December 10 From: Portland, OR Member No.: 12,501 Region Association: Pacific Northwest |
It hasn't been that many miles since I last adjusted the valves, but that was my first time so I wouldn't be surprised if I left one too tight.
I'll adjust the vales and re-check. Thanks for the help! |
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| DBCooper |
Jan 7 2012, 08:55 PM
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#7
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14's in the 13's with ATTITUDE Group: Members Posts: 3,079 Joined: 25-August 04 From: Dazed and Confused Member No.: 2,618 Region Association: Northern California |
After adjusting the valves if it's still low find where the loss is, from rings or valves. You can pressurize the cylinder (have an air compressor?) and listen in the intake and exhaust to see which is leaking. Or have someone do it for you. Valves are easier to fix than rings, but knowing which will make other larger decisions easier.
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| charliew |
Jan 8 2012, 08:07 PM
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#8
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Advanced Member Group: Members Posts: 2,363 Joined: 31-July 07 From: Crawford, TX. Member No.: 7,958 |
For a ring leak listen to the breather cap or oil filler cap with the air pressure test. Alsp putting light motor oil in the plug hole will reduce the ring leak. Never try to set a valve on the tight side. Gas motors usually run their smoothest with slightly loose valve settings.
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| PDXMike |
Jan 29 2012, 06:52 PM
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#9
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Slowly Learning Group: Members Posts: 111 Joined: 20-December 10 From: Portland, OR Member No.: 12,501 Region Association: Pacific Northwest |
Cylinder 1 intake was too tight. I adjusted everything and now I am between 120-130psi across the board. The idle even smoothed up a bit.
I'll keep an eye on it, but I assume it was too tight because I adjusted it incorrectly on my previous try. That was the first valve I adjusted on my first attempt, so a mistake seems very likely. |
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| euro911 |
Jan 29 2012, 08:05 PM
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#10
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,849 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California
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Glad to hear you found and fixed the problem (IMG:style_emoticons/default/beer.gif)
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