Compression test help

cmrokilr

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Just did a compression test on my Cobra cylinders 5-7 were all kinda on the lower side with cylinder #6 being 135 psi.. the original plugs were all gapped around .042 I put NGK TR6’s back in gapped at .035

Should I be concerned with the compression test results? Car is 100% stock with 11k
 

fivelitrecobra

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Usually 10% difference is acceptable between cylinders. 5, 6, & 7 are a little on the low side. I'm assuming your car is probably a 2003? Some 03's had issue's with the drivers side head and the lack of coolant flow to it, it would get hot and cook the valve seals over time. Cylinders 7 and 8 were usually the most common for this. I'm betting this is what is going on with your car. Any smoke on start-up?
 

P49Y-CY

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based on those numbers i don't think you need to be concerned at all. i would say just drive and enjoy!

three years ago i did a test on my upper-pulley terminator with well over 100k on it at the time. these were the results:

#1 - 170 psi (highest reading)
#2 - 150 (-12%)
#3 - 162 (-5%)
#4 - 157 (-8%)
#5 - 147 (-14%)
#6 - 141 (-17%)
#7 - 150 (-12%)
#8 - 165 (-3%)

but the car still runs and drives just fine, and i enjoy it everyday. yours is 100% stock with 11k? i'd say you're golden
 

cmrokilr

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Usually 10% difference is acceptable between cylinders. 5, 6, & 7 are a little on the low side. I'm assuming your car is probably a 2003? Some 03's had issue's with the drivers side head and the lack of coolant flow to it, it would get hot and cook the valve seals over time. Cylinders 7 and 8 were usually the most common for this. I'm betting this is what is going on with your car. Any smoke on start-up?
Correct it’s an early 03 but no smoke at start up. Doesn’t seem to have the head tick either
 

cmrokilr

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based on those numbers i don't think you need to be concerned at all. i would say just drive and enjoy!

three years ago i did a test on my upper-pulley terminator with well over 100k on it at the time. these were the results:

#1 - 170 psi (highest reading)
#2 - 150 (-12%)
#3 - 162 (-5%)
#4 - 157 (-8%)
#5 - 147 (-14%)
#6 - 141 (-17%)
#7 - 150 (-12%)
#8 - 165 (-3%)

but the car still runs and drives just fine, and i enjoy it everyday. yours is 100% stock with 11k? i'd say you're golden
I was thinking that too. It doesn’t appear to have loss of power or any codes. Appreciate the input
 

hotcobra03

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Was this done on a warm engine?

I've tested mine many times,

I've also had head issues.

1st head cylinder 6 dropped [email protected] ford replaced head.
2nd 120 k cylinder 6 again. Dropped Valve.fixed head .
3rd cylinder 7 cracked @200k
Replaced head with new design
@422k now.

Passenger head is original.

Maybe it's gauge difference.

I'm seeing 180lbs on cylinder 1-5.

6,7,8 195lbs

I did test 1 cylinder #5. With cold engine and the other 7 plugs in.
Seen 160lbs .

My car is dated 08/02 on door

According to cobra Bob facts and questions..
Car had 1st run plugs but different catch number on pcm.
Had green coolant .
 

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