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Compression test results |
Post Reply | Page 123 5> |
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FSJunkie
AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4741 |
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Posted: Mar/14/2014 at 8:06pm |
I wasn't able to do a compression test when I bought it, so I had to wait until now, several months later.
The technical service manual states 140 PSI compression pressure. No mention of minimum or maximum, just 140 PSI. 8.0 compression 1977 232 with the throttle and choke blocked fully open and all spark plugs removed: 1: 145 2: 145 3: 140 4: 115 (130 with oil) 5: 145 6: 145 Looks pretty good to me except that one cylinder. That's not super low compression, but I'm still concerned about it. This engine has also developed some noisy valves lately. Not very noisy, just a light ticking. Sometimes it's only one, sometimes it's two, and sometimes it's perfectly quiet. The warmer the engine is and the lower RPM, the more it tends to tick. It was perfectly silent when I bought it. I also noticed back then that this engine was pretty dirty and sludged up inside from having the wrong thermostat, no PCV filter, and probably lack of oil changes. I'm thinking my nice clean high detergent oil is flushing the crud through the lifters and plugging them randomly. Think that's what's causing it? The loudest of the tickers seems to be coming from near cylinder #4, so perhaps that lifter is plugged and causing the low compression numbers as well. Thoughts? |
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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pedal2themetal45
AMC Apprentice Joined: Mar/01/2014 Location: Boise Status: Offline Points: 27 |
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Hi, sounds like a good place to start... Might pull the rocker and see if maybe you bent a push rod easy place to start.. it wouldn't take much to make it tick..
As for the numbers 140 is most likely mim.. since some are 145 .. As long as they are with in 10 to 20 Lbs of each other it should be good..
good luck
Edited by pedal2themetal45 - Mar/14/2014 at 8:18pm |
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tyrodtom
AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6199 |
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The 3 and 4 cylinders on a AMC are usually the cylinders that tend to run rich. The cylinders walls get washed down with the rich gas mixture, and has faster ring wear. And that's what your numbers show.
Did you warm the engine up, before pulling the plugs ? A warm engine has higher numbers, usually. |
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16591 |
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and higher readings than what its called for sometimes means carbon build up. but possibly when it was rebuilt, the head may have been milled quite a bit
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carnuck
AMC Addicted Joined: Mar/31/2010 Location: Seattle Status: Offline Points: 3942 |
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The PCV is directed towards the center two cyls and may be gumming up the intake valves. I do the water trickle to get a truer reading.
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4419 |
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What is the "water trickle" treatment? |
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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carnuck
AMC Addicted Joined: Mar/31/2010 Location: Seattle Status: Offline Points: 3942 |
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While the motor is running at operating temp, slowly trickle water down the carb as you rev it (not redlining!) AKA decarburizing. Not enough water to stall or you could bend con rods.
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Got an Eagle?
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FSJunkie
AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4741 |
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I suppose the real question here is whether or not the ticking and low compression numbers are related.
Edited by FSJunkie - Mar/14/2014 at 11:40pm |
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7522 |
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how many miles on it
sounds like #4 is leaky. head rebuilds are nto that invasive. if qquirting oil in #4 didnt bring up the compression likely its a leaky valve. the good news is that head rebuilds are isolates events, and wont mess anything else up. a leak down tester (two gauges on a manifold) can disern bad valves vs. rings to a good aproximation. my experience is this, maybe parallells yours. when i started driving Ramblers, AMC was still in business. then they became "used cars". then "old cars". then.. antique cars. in some fashion, i the back of my head, i thought of them as "just old, used cars". the reality was, it was ike driing a Whiting, Diamond Reo, etc; i thought it was "NORMAL", to me, (bu i wrote good code in FORTRAN4 and 8x300 assembly language) but to the kids at the parts store, it mgiht as well have been some 1946 Roswell flying saucer. WTF is a "trunnion"!? "points"? what;s a generator? a "V" belt?! is that some sort of horse harness? my approach is to find another head. have that rebuilt. then swap. minimizes downtime, and cost is only sligtly higher. you also get two systems to compare. my father was into Model T's and Model A's. the leather cone clutch is as freaky and old to you and me, as a points ignition is to a 21 year old. its US that's the problem, not the kids! |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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uncljohn
AMC Addicted Joined: Jan/03/2013 Location: Peoria AZ Status: Offline Points: 5394 |
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A 77 232? 37 years old? Untold number of miles on it? Unknown maintenance over that time and one cylinder is a bit low and it comes up with oil?
It is a bit worn. O.K., It did not tick but now it does after how many miles? O.K., What at weight oil are you using? That will have some bearing on lifter noise. A 10 w 30 or 40 is fine. A 5 W anything is not. Probably things are getting cleaned out, I dunno. If it is a lifter they are not that hard to change on an in line 6 with out major disassemble. I have had a lifter tick on mine now for 14 years, if it gets any worse I might worry about it. Is it time to be concerned? I can not answer that. It does not sound it to me. If you want to freshen it up, pull the head and see what wear there is. I have never had any luck with a ridge reamer so if that is bad, you want to bore it to next over size with pistons and rings and then go from there. Or? Drive it a while, put heavier oil in it and call it good to go. OR? I have a 76 on an engine stand with about 75,000 miles on it. It could be available. I plane on using the other one with about 10,000 miles on it. |
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70 390 5spd Donohue
74 Hornet In restoration 76 Hornet, 5.7L Mercury Marine Power 80 Fuel Injected I6 Spirit 74 232 I-6, 4bbl, 270HL Isky Cam |
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