No compression after valve adjustment

[Halstead666]

I have a 1996 5.7 alpha mercruiser things were going fine until I decided to make a valve adjustment as I thought I might gain a little more on my top end if done properly........I know now that I should have left it alone but I could not help myself as the top end has only been going to 4000 and should higher as in the 4600's or so.....Anyways I did the valve adjustment as per the mercruiser manual for my engine or at least I thought I did as I marked the valves incorrectly when making each adj on TDC #1 then #6 ie i marked the exhausts as intakes and intakes as exhausts......thus no compression. After rereading the manual I discovered my error and then made the correct adjustments as TDC# Intakes - 1,2,5,7 & Exhausts- 1,3,4,8 then @TDC#6 Intakes -3,4,6,8 & Exhausts- 2,5,6,7 all adjusted one full turn once at zero lash. Figured this would do the trick and get me back to running normal again......put compression test on #1 and got 150 and was happy but then got 0's on the others?.????? I am pulling my hair out on this one and was wondering if you guys have any suggestions for a fix?

Mark Tiernan

 

[skippy2235]

1) Take all plugs out
2) loosen all the valves so they wont get pushed down, take off rocker arms.
3) do compression check.
If compression is good, then adjust valves again, paying better attention to the book.
If compression is NOT good, find out why, reasons that come to mind:
Bent pushrods, valves, wrong adjustment procedure.

 

[Halstead666]

Hi, ThAnks for the quick reply...........When I loosen all the valves and take rocker arms off should I remove the rods before I do compression test? Also if there are no push rods or rocker arms on the valves will I be able to do this compression test as all there will be no movement in any valve. Or is thAt the point?

 

[skippy2235]

If you can remove the push rods go for it, and yes that is the point. Test that the valves are sealing.
you may not get awsome readings, but you are looking for any reading. that tells you valves are closed.
If all valves are closed, then you messed up the adjustment.
or bent a pushrod, so look for bent ones.

 

[Bondo]

Ayuh,.... Welcome Aboard,.... Just loosen the valves, turn the motor on the starter, to pump up the lifters, then readjust, Properly,.....
Yer lookin' for Zer0 Lash, forget that twistin', 'n turnin' the pushrod Bullship,....

I'm guessin' ya collapsed a lifter or three, causin' yer problem,....

Btw,... Loss of top end is usually a fuel delivery issue,....

 

[alldodge]

Could loosen the valves up and get it running, then as its running at idle adjust valves. To do this start to loosen more a bit till the engine starts missing. Then turn back slowly 1/4 turn at a time till it stops. Once stopped slowly, turn 1/4 turn more in.

Bondo has your top end answer

 

[Halstead666]

Thanks again! As a follow up I did as suggested and got readings of 150 #1 and was happy but then 60 on the rest.....then I closed everything up and great readings nothing lower than 150 on a cold engine.........then it fired up .......did the timing and things are now running great! thanks for the help I actually redid the adj 4 times before going to the forum and following your suggestion......