Compression Question
10-13-2009, 04:27 PM
#1
6th Gear Member
Thread Starter
Join Date: Jan 2007
Location: Milford, Delaware
Posts: 5,464
Compression Question
Is it possible to have low compression in a few clyinders from the top end maybe roller rockers not set properly. After my head swap I was getting alot of smoke and a few clyinders had low like 50psi compression hoping its not bottom end the bottom end looked good when I took the heads off
10-13-2009, 05:01 PM
#3
1st Gear Member
Join Date: Jan 2005
Location: Corryton, TN 37721
Posts: 127
I agree it is most likely the top part since you did the heads recently. What you can do is squirt some motor oil into the hole where the spark plug goes, and recheck compression. The few drops of oil will temporarily seal the lower part, rings and cylinder wall. If the compression goes back up, then it is likely the rings. If it remains about the same as before, then you know it is the upper half.
10-16-2009, 02:35 AM
#6
4th Gear Member
Join Date: May 2005
Location: California
Posts: 1,259
How did you go about tightening the roller rockers? If they are overly tight that can very easily cause low compression. I know there are a couple ways to do it but one way to do it that I use is to get each cylinder to Top Dead Center, then tighten the rockers to about 20 ft/lbs and repeat the process for all 8 cylinders.
10-16-2009, 08:22 AM
#8
2nd Gear Member
Join Date: Jan 2006
Location: Colorado
Posts: 384
Don't want to discount information so i'm asking questions on 94ford5liter's information:
Atleast the base of the lobe TDC alone i dont think will do it. but i'm not an expert, just have done it a couple of times. is this a way you would adjust pedistal? I really think there is more to it then this.
Not sure on the 20 ft pounds one either? I've never heard that before. I have heard half or three quarter turn past zero lash. Technically if dealing with hydraulic lifters you will never be in a perfect condition where 20 ft-lbs will put you in the same spot every time. even with Pedistal mount you would have to check the clearance first.
Atleast the base of the lobe TDC alone i dont think will do it. but i'm not an expert, just have done it a couple of times. is this a way you would adjust pedistal? I really think there is more to it then this.
Not sure on the 20 ft pounds one either? I've never heard that before. I have heard half or three quarter turn past zero lash. Technically if dealing with hydraulic lifters you will never be in a perfect condition where 20 ft-lbs will put you in the same spot every time. even with Pedistal mount you would have to check the clearance first.
How did you go about tightening the roller rockers? If they are overly tight that can very easily cause low compression. I know there are a couple ways to do it but one way to do it that I use is to get each cylinder to Top Dead Center, then tighten the rockers to about 20 ft/lbs and repeat the process for all 8 cylinders.
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