TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC 6 Cylinder Engine Repair and Modifications
  New Posts New Posts RSS Feed - Compression test results
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

Compression test results

 Post Reply Post Reply Page  123 5>
Author
Message
FSJunkie View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/09/2011
Location: Flagstaff, AZ
Status: Offline
Points: 4741
Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Topic: Compression test results
    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?

1955 Packard
1966 Marlin
1972 Wagoneer
1973 Ambassador
1977 Hornet
1982 Concord D/L
1984 Eagle Limited
Back to Top
pedal2themetal45 View Drop Down
AMC Apprentice
AMC Apprentice
Avatar

Joined: Mar/01/2014
Location: Boise
Status: Offline
Points: 27
Post Options Post Options   Thanks (0) Thanks(0)   Quote pedal2themetal45 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2014 at 8:15pm
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
Back to Top
tyrodtom View Drop Down
AMC Addicted
AMC Addicted


Joined: Sep/14/2007
Location: Virginia
Status: Offline
Points: 6199
Post Options Post Options   Thanks (0) Thanks(0)   Quote tyrodtom Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2014 at 9:10pm
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.
66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
Back to Top
purple72Gremlin View Drop Down
AMC Addicted
AMC Addicted
Avatar
Charter Member

Joined: Jul/01/2007
Location: Illinois
Status: Offline
Points: 16591
Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2014 at 9:33pm
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
Back to Top
carnuck View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Mar/31/2010
Location: Seattle
Status: Offline
Points: 3942
Post Options Post Options   Thanks (0) Thanks(0)   Quote carnuck Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2014 at 10:17pm
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.
Back to Top
bikerfox View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: Aug/02/2009
Location: USA
Status: Offline
Points: 4419
Post Options Post Options   Thanks (0) Thanks(0)   Quote bikerfox Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2014 at 10:48pm
Originally posted by carnuck carnuck wrote:

I do the water trickle to get a truer reading.



What is the "water trickle" treatment?
1969 Rebel SST (1970-1987)
1968 AMX (2005-2011)
1969 SC/Rambler (2011-2019)
1970 Javelin (2019 to ?)"Jane"
Back to Top
carnuck View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Mar/31/2010
Location: Seattle
Status: Offline
Points: 3942
Post Options Post Options   Thanks (0) Thanks(0)   Quote carnuck Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2014 at 11:16pm
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.
Back to Top
FSJunkie View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/09/2011
Location: Flagstaff, AZ
Status: Offline
Points: 4741
Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2014 at 11:36pm
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
1955 Packard
1966 Marlin
1972 Wagoneer
1973 Ambassador
1977 Hornet
1982 Concord D/L
1984 Eagle Limited
Back to Top
tomj View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/27/2010
Location: earth
Status: Offline
Points: 7522
Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Mar/15/2014 at 12:53am
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!


1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5
http://www.ramblerLore.com

Back to Top
uncljohn View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/03/2013
Location: Peoria AZ
Status: Offline
Points: 5394
Post Options Post Options   Thanks (0) Thanks(0)   Quote uncljohn Quote  Post ReplyReply Direct Link To This Post Posted: Mar/16/2014 at 8:19pm
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.


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
Back to Top
 Post Reply Post Reply Page  123 5>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.203 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or