compression test results ?

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Joined
Nov 4, 2013
Threads
5
Messages
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Location
Yonder Mountain
Background...truck has been sitting for probably two months. Been doing some work to it; transfer case rebuild, h55 and some other stuff. Its and 87 with 188,000. Ive only put maybe 500 miles on it in the year or so that ive had it. Just messing around today did a compression test, cold since nothing is really hooked up. Here is what we got...
157
135
140
115
130
130

The range scares me. I know the PO had the head off and resurfaced due to a blown head gasket at 183,000. We have done a valve adjustment recently so they should be inline.In a perfect world we would have done this hot but given the circumstances we couldnt. i dont want to wait until everything is back in place in case I want to pull the motor. Is this a cause for concern in yall opinion? Thanks
 
It's hard to make a call when you can't do a proper test,make sure your your cranking speed stays the same when cranking and try doing a wet compression and see if it gets better and make sure all the plugs are out and throttle wide open.
 
what I'd take from those numbers is, that I need to do a good solid valve adjustment using stock specs but on a cold motor AFTER checking that the head bolts are all at factory torque spec( don't back off, just turn the head in the tighty direction with the wrench set to mid range spec and make sure it "clicks" Use a crowfoot wrench on the bolt under the rocker shaft if you don't want to yank the rocker shaft before the head bolt torque. set valve lash as tho it were initial post overhaul lash setting. remove all plugs and block the throttle wide open with the choke wide off. either charge the battery first, or have some jumper cables hooked to a running vehicle to keep the starter spinning at a consistent rate for the test(important). disconnect the coil so it doesn't get hot during the test and to minimize risk of uncontrolled spark in engine comp while testing. crank 5-6 revs per cylinder per reading. take 2-3 readings per cylinder and record results. valves get tight on the exhaust side and loose on the intake- this can have adverse affects on compression and performance as the exhaust won't close all the way and compression escapes before it can be used while a loose intake will bring in less volume overall to escape before it can be used...hth
 
oh and use highest recorded values for each cylinder to do you range...
 
just noticed you have done valve lash recently...might do another one to be sure- it's easier than replacing a head/gasket/or overhaul the engine. if still questionable, do a cycle with a few drops of oil from a turkey baster per cylinder, just make sure to add the same volume of oil per cylinder to keep your range...those numbers with decent valve lash could be worn rings(or stuck ring)
 

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