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PostPosted: Sat Dec 10, 2011 11:04 am 
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EFI Slant 6
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Joined: Wed May 28, 2003 9:08 am
Posts: 373
Location: Chelsea, MI
Car Model: 71 Dodge D100 64 Plymouth Valiant Wagon
So after finally getting a bolt I though I could turn my engine by hand or use and air wrench to get a compression reading. No luck.

The engine has been sitting a number of years. Half a not-too-dirty quart of oil low. I was concerned that putting oil in would give an inaccurate reading.

Tips?

Your expertise is always appreciated,

Joe

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Joe Hoppe

71 D100 225 Super Six 727 AT on 2008 Crown Vic CopCar frame

64 Valiant Wagon 225 904 AT 3:23 8.75"


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PostPosted: Sat Dec 10, 2011 8:03 pm 
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Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6291
Location: So California
Car Model: 64 Plymouth Valiant
Bolt on the starter and hook up a battery with jumper cables.

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64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

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PostPosted: Sat Dec 10, 2011 8:20 pm 
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Joined: Mon Mar 31, 2003 1:04 pm
Posts: 7457
Location: Oregon
Car Model: 2023 Eichman Digger?
It's on an engine stand?

CJ

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PostPosted: Sat Dec 10, 2011 8:50 pm 
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6 Pack Dart
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Joined: Sat Nov 02, 2002 5:44 pm
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Location: Eugene, Oregon
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No way you could spin motor over to get compression test by hand or air impact wrench. you need to have it spinning at starter speed!

Richard

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PostPosted: Sat Dec 10, 2011 8:50 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13278
Location: Fircrest, WA
Car Model: 76 D100
Use a thread in compression tester and crank it over by hand so the motor goes through three compression stroke on the cylinder you are checking. Try and rotate the motor so the compression stroke is completed in one continuous crank to avoid too much bleed down.

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PostPosted: Sat Dec 10, 2011 8:52 pm 
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Board Sponsor & Contributor

Joined: Thu Oct 31, 2002 5:39 pm
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Location: North America
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You have to be able to crank the engine to do a compression test, which means you need a flywheel and bellhousing. If the engine (and only the engine) is bolted to a stand, there's no way to do the test. And you can't really do a good compression test on an engine on a stand, because the engine's not warmed or warmable up to operating temperature. Easier to pull the head and do a visual inspection.

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PostPosted: Sat Dec 10, 2011 10:20 pm 
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EFI Slant 6
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Joined: Wed May 28, 2003 9:08 am
Posts: 373
Location: Chelsea, MI
Car Model: 71 Dodge D100 64 Plymouth Valiant Wagon
Dan---

A link to what I should be looking for? Way to measure ring gap or something like that?

Joe

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Joe Hoppe

71 D100 225 Super Six 727 AT on 2008 Crown Vic CopCar frame

64 Valiant Wagon 225 904 AT 3:23 8.75"


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PostPosted: Sat Dec 10, 2011 10:34 pm 
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Site Admin
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Joined: Mon Mar 31, 2003 1:04 pm
Posts: 7457
Location: Oregon
Car Model: 2023 Eichman Digger?
What tools do you have at your disposal?
If it's out of the car on a stand, tear it down and use micrometers to determine what condition all parts are in.
If it's been sitting that long, it needs new seals anyway. Time to go through it with your machinist and buy a complete engine gasket kit. You can wait to buy that until you find out if you need to kit the engine. If you buy a master engine rebuild kit, the gaskets come with it.
If you don't have the tools to go through the engine and make your own measurements, take it to a local machine shop and have it checked out.

The rule on ring gap is "3 to 4 per inch of bore." Stock bore is 3.4 so 10 to 14 thousandths.


CJ

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PostPosted: Sat Dec 10, 2011 10:55 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13278
Location: Fircrest, WA
Car Model: 76 D100
Hmmm. Maybe that is why the last slant I did a compression check on while it was on an engine stand had low compression! :lol:

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PostPosted: Sun Dec 11, 2011 4:20 am 
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SL6 Racer & Moderator
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Joined: Sat Oct 19, 2002 12:06 pm
Posts: 8978
Location: Silver Springs, Fl.
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You can do a leak down test on the engine stand. This will give an indication of the condition of the engine.

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