no compression

hey guys! my 1982 Z28E is yet again doing my nut in. there was a slight popping from the exhaust so i was told to adjust the valves as one or two of the nuts might of losened and causing it to open/close too soon/late. so with my chiltons manual i followed the instructions. losen off the nuts till play is felt at the push rod and tighten till lash is emilinated at the push rod then tighten one full additional turn. (i assume one 360 degree turn) in the order the book tells me too.
and now? no compression! i redone it several times and still nothing. i should of just left it alone! its been 12 weeks now sitting on my drive and no one knows whats up with it. the engine spins, sparks and plenty of fuel, it just ain't firing due to no compression. any help would greatly appriehated, especacially as i'm the UK with loads and loads of cars to thrash off the lights!! :grinyes:

Turn the motor so both lifters on the same cylinder are down. Then tighten till zero lash, then go a 1/4 turn past that.

i thought it was a half turn?

EDIT: no sorry, that was something else, youre right 1/4 turn...

are you sure you turned the engine over 360 in the right direction??? if you turned it backwards it would be off i believe. id have to sit and figure out exactly how that would cause your problem though.

Adjusting Valves and Zero Lash



Zero lash is when you go from having slack between the lifter, pushrod and rocker arm, to the exact point of no slack. The lifter needs to be on the base of the lobe when setting valve lash. When a cylinder is at TDC, both lifters should be at the bottom of their travel (base of the cam lobe).

Gauging zero lash by hand is not an exact science. When setting the valve lash with the engine not running, you can get close enough by doing the "spin the pushrod" method. Loosen the rocker arm until you can feel slack in the pushrod to rocker arm. Spin the pushrod with your fingers while tighening the rocker arm back down. When you BEGIN to feel drag while spinning the pushrod, you are at zero lash. Once zero lash is reached, stop and add your preload. DO NOT go back and try to feel the adjustment. The lifter will immediately begin to bleed down a little. Tension on the pushrod will relax and this will make it seem like your adjustment did not work. If you want to recheck zero lash, you must loosen the rocker arm nut and tighten it down again while spinning the pushrod as before. At that point you want to set the preload and LEAVE IT ALONE.
The hydraulic lifter has an internal plunger that has a specific amount of travel. On stock engines, the purpose of preload is to compress the plunger so the pushrod will be centered within that travel. With stock lifters, turning the rocker nut another 1/2 to 3/4 turn, will normally put you in the ballpark for quiet operation without being too tight. Specific lifters like the Comp Cams "Comp R's", have less internal travel. 1/4 turn preload is more than plenty, with 1/8 or just barely any preload being better for high revving engines. Comp actually recommends .002-.004 preload on a warm engine.

Consequences of improper adjustment:
Too tight - the valves will not completely close and you will lose compression. The engine will run rough, if it will run at all.
Too loose - the rocker arms will make noise from the slack and pushrods could be dislodged. Possible damage could occur from either extreme.



Engine Running Method

Some like to adjust the rockers while the car is idling. If you wish to do this, loosen one rocker at a time until you can hear it click. Tighten the nut, but don't exert downward pressure on the rocker arm with your socket. At the point when audible clicking is gone, tighten the nut another 1/4 turn for your preload (Comp R lifters, less as noted above).



Engine Not Running Methods
There are several methods for setting the lash with the engine not running and are listed below.




Method 1

If you have never had the crank hub off (or know for sure that it's orientation is correct), you can use the arrow that is on the balancer to tell you where you are. You don't have to spin the crank every 90º with this method.
When the arrow is at 12 o'clock you will be at either #1 or #6 TDC. You might have trouble identifying whether #1 or #6 is at TDC when the crank arrow is at 12 o'clock. Probably the easiest way is to look over the other valves. Compare them to the charts below, showing which can be adjusted. Any valve that can be adjusted should be UP. Valves that are not to be adjusted will be in varying degrees of being open or DOWN. I used to say to look at the valves on the #1 and #6 cylinders, but sometimes it can be difficult to tell by those cylinders only. After looking at the charts below and your valves, you should have it figured out rather quickly.

When at #1 TDC you can adjust the following valves:

Intake: 1, 2, 5, 7
Exhaust: 1, 3, 4, 8

Rotate the crank one revolution until the pointer is again at 12 o'clock. This will let you adjust the remainder of the valves. If you did #1 the previous time, you should be now at #6 TDC.

When at #6 TDC you can adjust the following valves:

Intake: 3, 4, 6, 8
Exhaust: 2, 5, 6, 7



Method 2


If you want to set the lash by bringing each cylinder to TDC, watch the valves and the pointer on the balancer and follow the Firing order:

1-8-4-3
6-5-7-2
Adjust both intake and exhaust of the cylinder that is at TDC. You will have to make 2 revolutions of the crank, stopping at 1/4 (90º) turn intervals for each cylinder.



Method 3


Another cylinder by cylinder method that does not require looking at the balancer position, follows:

(A remote starter switch is quite helpful)
Turn the engine in the normal direction of rotation until the exhaust lifter for a cylinder starts to move up, then adjust the intake valve to zero lash and add your preload. Turn the engine over again until the intake opens completely and then is almost all the way back down. Now, set the exhaust valve to zero lash and add your preload. Continue the above procedure for each cylinder until all valves are adjusted to the same amount of preload. This procedure will work for any hydraulic lifter cam with adjustable rocker arms.



Poly Locks


Here is something additional for those that use "poly locks" (typically used with roller rockers).

Since the poly lock is not a prevailing torque fastener like the nut used with the stock rocker and ball arrangement, it spins freely on the rocker stud. This gives you an advantage to finding zero lash. With the allen lock backed off, spin down the nut until it just stops. This is very close, if not right on zero lash in most cases. Check your pushrod for proper movement and play with it to get a feeling just how snug or loose the nut should be to obtain zero lash. Once you do that, you can just use the nut to reach zero lash and not have to worry about messing with the troublesome pushrod. This will speed up your valve adjustment.

Another aide is to make a mark on the top of the nut so that you can easily see how far you have turned the nut. I always found it a little difficult to obtain the exact amount of rotation on the nuts under the cowl, because of there being less room to swing a ratchet or other tool handle. I used a little dab of white paint on the top and was easily able to tell when I made a half turn or whatever was needed. I could also just use a wrench to tighten the nuts, then throw the allen wrench on it and snug the set screw down (while holding the nut).

Some like to run the allen set screw down and then tighten it and the nut together. Whichever method works and stays tight for you should be fine. With all the variables in making adjustments to hydraulic lifters like the number of turns for preload, methods of finding zero lash and trying to see what you are doing under the cowl, slight errors are common. Just try to be as consistent as possible and use the method that works best for you.

and thats the short explination ;)

and thats the short explination ;)

lol, thats what i thought!!! we have to help the guy out right???

Adjusting lash while car is running...... never heard of that before. I 'm not liking it.

i do mine like the book says and like twdz28 said, just to get it running, then when it's warmed up i adjust them with it idling...like twdz29 said

yeah, adjusting while the engine is running is kinda the "do it by ear" way, you loosen a nut till it starts lightly tapping, then tighten her till it stops tapping, then a half turn more or something like that.