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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
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89 2.3 Turbo, 82 T-Top Notch 5.0, 86 LX T-Top 5.0 roller and 86 GT Black in and out with Gt 40X Heads, Smoothed Engine Bay, Battery in Trunk, SLP's, Bolt-on's
Vehicle: 1990 5.0 LX 7 UP and 2009 Premium Convertible
Location: Knoxville, TN and Biloxi, MS
Posts: 35
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.
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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1994 cobra - too many mods to list.
266 rwhp 316 rwtq at 82'F with just setting up the A/F on a pretty basic setup, AFR 165s w/stock cam through a tko 600. Newest addition - car blew the timing chain cover gasket so put in a b303, tune next friday.
Old Car Sold February 08 -
1994 Mustang Gt 5spd -
322rwhp,346rwtq
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.
Quote:
Originally Posted by 94ford5liter
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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Compression Question
