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Compression test results

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Old Oct 18, 2016 | 05:55 PM
  #1  
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From: SALEM, NH
Car: '88 Formula
Engine: LC9
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Axle/Gears: 3.89 9"
Compression test results

What do you guys think of these two cyls:

#7


#1


-- Joe
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Old Oct 18, 2016 | 06:18 PM
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Re: Compression test results

Low , here's a Friend's 1969 Rambler 390 at 75K miles , all cyls were within a few PSI of this .
Attached Thumbnails Compression test results-rambler-6.jpg  
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Old Oct 18, 2016 | 06:38 PM
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Axle/Gears: 3.89 9"
Re: Compression test results

It's a 9:1 blower motor. I meant more of the needle movement rather than the final pressure.

-- Joe
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Old Oct 19, 2016 | 06:44 AM
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Re: Compression test results

Originally Posted by anesthes
It's a 9:1 blower motor. I meant more of the needle movement rather than the final pressure.

-- Joe
Ah , it's built for boost , got it .

As to the movement , it looked normal to me . I know that any time Ive ever done compression tests the needle usually bumps up once or twice to a final pressure like yours did , in fact I can't ever recall seeing one do one big push up to it's top pressure with no further increases , if that's what your asking .
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Old Oct 19, 2016 | 08:51 AM
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Re: Compression test results

Seems like it cranks slow? But seems normal to me
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Old Oct 20, 2016 | 05:53 AM
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From: SALEM, NH
Car: '88 Formula
Engine: LC9
Transmission: 4L60E
Axle/Gears: 3.89 9"
Re: Compression test results

Originally Posted by Orr89RocZ
Seems like it cranks slow? But seems normal to me
The #7 cylinder has a final psi reading of almost 10 lower than all the others. This cylinder was also glowing the header primary at idle. Trying to determine if it is bad injector, or valve issue.

As far as the engine rotating slowly, I've never been able to figure that one out. It's got 150psi compression which isn't high at all, and my bearing clearances are loose. Yet it is hard to turn over by hand or starter.

-- Joe
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Old Oct 20, 2016 | 01:22 PM
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Re: Compression test results

.
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Old Oct 20, 2016 | 04:37 PM
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From: SALEM, NH
Car: '88 Formula
Engine: LC9
Transmission: 4L60E
Axle/Gears: 3.89 9"
Re: Compression test results

Forgot to post the plugs. #7 and #8 look sooty (well moreso than the rest). The ground electrode anyhow, where it's clean on the others.

Overall the motor seems rich, although the wideband indicated like 15:1.. My plug gap was .045 though, which might be too wide for these chambers. I dunno.
Attached Thumbnails Compression test results-img_20161018_173140.jpg   Compression test results-img_20161018_173150.jpg  
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