460 testing compression
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Elder User
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From: East Norriton,PA
460 testing compression
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i have a 77 460 that i pulled from a local u pullit for
a whopping $1 yes thats one dollar, it was a special..it
actually costed me $20 to get in and all parts were a $1
anyway, i get it home put it on a stand, and go to
check compression and it has NONE...barely 30 pounds in 2 cylinders...Now this is with the carb and plugs out and the
air pump removed etc...Where should i check next???Can this
be possible???I can hear compression, but it seems not on every
turn of the crank..I check the compression gauge on another
motor and it does work fine..
i have a 77 460 that i pulled from a local u pullit for
a whopping $1 yes thats one dollar, it was a special..it
actually costed me $20 to get in and all parts were a $1
anyway, i get it home put it on a stand, and go to
check compression and it has NONE...barely 30 pounds in 2 cylinders...Now this is with the carb and plugs out and the
air pump removed etc...Where should i check next???Can this
be possible???I can hear compression, but it seems not on every
turn of the crank..I check the compression gauge on another
motor and it does work fine..
Senior User
Joined: Aug 2001
Posts: 213
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From: Six Shooter Junction
460 testing compression
[font size="1" color="#FF0000"]LAST EDITED ON 14-Sep-01 AT 01:57 PM (EST)[/font][p]Well there buddy, you get what you pay for. Tear it down and check the internals. if you have one cylinder leaking into another, and no spark plugs in it, most of the compression excapes. The air is going to take the path of least resistance weather it be through a crack or bad seals. If its easier for the air to go through seals or a crack than to register on the gauge its gunna do it. All meaning it needs a rebuild if every thing else is ok.
Hope this helps
Chase
1979 F-250 4x4
71 460 Holley650, MSD OFFROAD
C6-B&M Transpack
Dana HD44Front/60Rear 3.73 Limited Slip
35 inch Goodyear Implement Tires
4 inch Skyjacker System
Will get souped up soon
Hope this helps
Chase
1979 F-250 4x4
71 460 Holley650, MSD OFFROAD
C6-B&M Transpack
Dana HD44Front/60Rear 3.73 Limited Slip
35 inch Goodyear Implement Tires
4 inch Skyjacker System
Will get souped up soon
Postmaster
Joined: Mar 2001
Posts: 4,968
Likes: 3
From: So Cal
460 testing compression
Yeah, most of those jumk yards know what they got and they almost never give anything away. Most likely that engine was a totally worn out war horse in need of a complete rebuild. Although I suspect that he wouldn't give it away for $1 if it had a rebuildable core. The other possibility is that someone left the engine open and over the years water got in and rusted things so maybe the valves are stuck/busted, timing chain busted, piston rings dissolved into rust.
But from the sounds of it, at best, you have a block that requires a full rebuild. At worst, you may just have a pile of parts that might be usable in some other engine.
Sorry, hope we are wrong.
Jim Henderson
But from the sounds of it, at best, you have a block that requires a full rebuild. At worst, you may just have a pile of parts that might be usable in some other engine.
Sorry, hope we are wrong.
Jim Henderson
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Elder User
Joined: May 2001
Posts: 646
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From: East Norriton,PA
460 testing compression
the motor only had 77,000 miles, and the yard i pulled it
from won't test motors from 91 on back(its not worth there time)
as they say. Well i guess its time to tear it apart..
from won't test motors from 91 on back(its not worth there time)
as they say. Well i guess its time to tear it apart..
Posting Guru
Joined: Aug 2000
Posts: 2,416
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From: PacNW
460 testing compression
group
i have a 77 460 that i pulled from a local u pullit for
a whopping $1 yes thats one dollar, it was a special..it
actually costed me $20 to get in and all parts were a $1
anyway, i get it home put it on a stand, and go to
check compression and it has NONE...barely 30 pounds in 2 cylinders...Now this is with the carb and plugs out and the
air pump removed etc...Where should i check next???Can this
be possible???I can hear compression, but it seems not on every
turn of the crank..I check the compression gauge on another
motor and it does work fine..
i have a 77 460 that i pulled from a local u pullit for
a whopping $1 yes thats one dollar, it was a special..it
actually costed me $20 to get in and all parts were a $1
anyway, i get it home put it on a stand, and go to
check compression and it has NONE...barely 30 pounds in 2 cylinders...Now this is with the carb and plugs out and the
air pump removed etc...Where should i check next???Can this
be possible???I can hear compression, but it seems not on every
turn of the crank..I check the compression gauge on another
motor and it does work fine..
I've seen a lot of "All you can carry in 1 trip for $5.00" and similar junkyard sales so I know what you mean.
Senior User
Joined: Mar 2000
Posts: 360
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460 testing compression
Pull one or both valve covers off. It may be obvious, like bent push rods, valves stuck, etc. Maybe no cam rotation, like broken chain as mentioned. A cylinder with both valves closed still can show very low compression, not always zero, air slips by. May even wheeze for a moment after you turn off the starter. Not necessarily toast yet.
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Elder User
Joined: May 2001
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From: East Norriton,PA
460 testing compression
I'm turning the motor over by socket and ratchet..could this
be a problem???
be a problem???
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Freshman User
Joined: Sep 2001
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From: Central Ohio
460 testing compression
Normally you test compression using the starter, perhaps it's not as bad as you first thought :-)
Do you know anyone with the gear and experience to do a leakdown test on it ?
Brian
Do you know anyone with the gear and experience to do a leakdown test on it ?
Brian
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Posting Guru
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From: PacNW
460 testing compression
I'm turning the motor over by socket and ratchet..could this be a problem???
Senior User
Joined: Mar 2000
Posts: 360
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460 testing compression
I didn't catch that it wasn't in the truck yet. I know I sure couldn't spin a 460 fast enough with a rachet for meaningful compression numbers! As others said, at starter speed with a charged up battery for at least 5 power strokes or so for the cylinder under test to get relevant numbers.
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Elder User
Joined: May 2001
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From: East Norriton,PA
460 testing compression
thanks guys
yes it does make pressure and push my finger off the holes...
so the hand cranking is the problem..Could i mount a starter
and turn it over on the engine stand???
yes it does make pressure and push my finger off the holes...
so the hand cranking is the problem..Could i mount a starter
and turn it over on the engine stand???
Senior User
Joined: Jun 2001
Posts: 480
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From: Alabama
460 testing compression
What are you wanting to do with the motor? Just drop it straight in a car or truck? You only have what $1 in it now right? If you have it on the stand, I would at least go through and put new seals, and gaskets on it. That would give you an opportunity to look inside the engine. If it needs a full rebuild you are still way ahead on the money end of things. Heck I paid 300 for a 460/c-6 out of a lincoln that was running, with the full intention of rebuilding it with forged pistons, solid cam, etc..
Basically don't worry about the compression test too much unless you are going to just drop it in something.
chris
79 F-150 Ranger Lariat, 2wd, RC, LB, 460 (intake, headers, cam), C-6(shift kit).
79 mustang (work in progress...its just slow progress)
98 Chevy 4x4 (work truck)
95 Lexus SC300 (wife's baby)
Basically don't worry about the compression test too much unless you are going to just drop it in something.
chris
79 F-150 Ranger Lariat, 2wd, RC, LB, 460 (intake, headers, cam), C-6(shift kit).
79 mustang (work in progress...its just slow progress)
98 Chevy 4x4 (work truck)
95 Lexus SC300 (wife's baby)
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