Cylinder Compression Test and Borescope at 110k

[MRX330]

Already been done son by Mitch at CP-E I will add....great guy! Very knowledgeable...owns a FiST himself and still rolling a C39 turbo from DHM for many many moons he told me and no issues.

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See post #11

 

[STationwagon]

I just got finished with a compression test at 126,000... found almost identical results:

Cylinder #1 - 180 psi
Cylinder #2 - 180 psi
Cylinder #3 - 179 psi
Cylinder #4 - 179 psi

What is “factory new” compression test look like? Hard to believe these high(er) mileage examples are testing so well.

 

[PrinceEdward IV]

I just got finished with a compression test at 126,000... found almost identical results:

Cylinder #1 - 180 psi
Cylinder #2 - 180 psi
Cylinder #3 - 179 psi
Cylinder #4 - 179 psi

What is “factory new” compression test look like? Hard to believe these high(er) mileage examples are testing so well.

i know its been 2 years since anyone replied to you

but i just did a compression test at 45k miles on my 2017 st

1 175
2 180
3 170
4 170


i feel like i didnt screw the compression tester nozzle into the spark plug holes as tight as i could have, but im making basically the same compression as you guys, so id say youre probably as close to factory as it gets.

the "official" compression in psi according to Ford is "160- 170" so anything above 160 is perfect, as long as all four are within 15-20psi of each other

 

[Mega ST]

Did a compression test today due to loss of MPH on my dragy runs. I usually trap 110-112 but lately was only seeing 108 and now like 106ish. Same area for testing and the weather has been much cooler than my other runs which should give me even more power. I did an accidental 2-1 shift and saw 7800-8000rpm even though I pushed the clutch back in immediately. Thought maybe some valve piston contact could be affecting compression and thus power. Numbers were

#1: 176
#2 185
#3 180
#4 175

I don’t think that small diff should affect power. Try some new plugs next. These have probably 20k on them, but no misfires. Anyway some compression data for anyone else doing a test. Motor has 106k on it.