Compression on Half the engine - Mustang Evolution

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Old 05-26-2013, 09:12 PM   #1
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Compression on Half the engine

Hey guys,
So this evening I decided to check compression and because I'm working in a tight garage I gave up early so I will probably redo the entire process.

That being said I got rough compression figures on the 2nd cylinder bank (5-8)
5) 90-100 psi
6) 90-100 psi
7) 100-110 psi (this spark plug had a slightly different color to it)
8) 90-100 psi


I just wanted to get your opinions on it I had thought compression was supposed to be higher in general, the only worrying thing is if 7 was as high as I think it might have been (115psi) but luckily the other three pistons seemed pretty similar. When I redid my E7TEs about 1.5-2k miles ago (due to overheat 3 days after I bought it) I redid my spark plugs and cleaned the cylinder tops.

I checked by using the starter to turn the engine over fyi (disconnected the ignition coil)
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Old 05-27-2013, 03:49 PM   #2
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Really? No one has any knowledge of 302 compression ??
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Old 06-01-2013, 07:05 PM   #3
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They are good and they deal with older engines like that all the time.
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Old 06-01-2013, 09:54 PM   #4
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depends on how much dynamic compression the camshaft has. 110 does seem low, was the engine cold? , not calling anyone ameture here or anything but that is a mistake alot of guys make, the engine must be warm when checking compression, throttle wide open as well.

the concern is also more on how many turns it takes to get to the max reading than what the max reading is.. usually.1-2 is very good 2-3 is good anything more is starting to show signs of wear.
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Old 06-01-2013, 10:00 PM   #5
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Agreed it needs to be 180 degrees or warmer and those numbers are very low but all uniform so I'm guessing you didn't get the car warm before testing or one would be way off if there was something wrong.

Procedure for pushrod:

-Get engine temp to operating temp
-Remove all plugs (wear good gloves, the headers/engine will be yoga balls hot)
-Disconnect coil wire
-Install gauge on 1st cylinder
-Crank engine for about 10 seconds
-Check gauge
-Move gauge to 2nd cylinder
-Repeat

General rule is less than 10% variance between highest and lowest reading.
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Old 06-02-2013, 12:48 AM   #6
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Thanks so much, engine was cold.
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