Hi,

I`have two short questions about setting the valves by using a compression gauge.
Do I turn the rocker arm nuts further down while the starter is turning oder should I do it step by step? Start - look at gauge - turn - another start - look at gauge and so on?
And can I lossen the nut(s) a little bit after I tightened it too far so that the compression has gone so that I have maximum compression or do I need to loosen the rocker arm nuts completely and start again?

Greetings from Germany!
Flo

 

The problem is that my valves on the passenger cylinder head are rattling very loud. The engine has no power when I want to drive up a hill. The acceleration is poor. I measured compression - each cylinder has about 210 psi which be good for a 100k miles engine.
What do you all think? Do the valves maybe open not far enough so that maybe not enough fuel-air-mix comes into the cylinder and thus the engine is not able to burn enough fuel-air-mix to accelerate fast?

Greetings from Germany!

Flo

 

210 PSI is good for ANY engine. Instead of the valves, I'd be looking at the rods as the source of the knocking (tapping) noise. I would also check my timing, as incorrect timing can cause that noise, which happens to be pinging/detonation in your cylinders.

BTW, the proper way to set your valves is to remove and clean the pushrods, reinstall, tighten the rockers until you can no longer move the pushrods vertically, then tighten another quarter turn. Without running the engine or using the starter.

 

Why are you trying to use a compression gauge to set valve lash?

 

Problem with setting valves with a compression gauge is that your doing it with no oil pressure. Once oil pressure kicks in, it lengthen the distance, thus making your valves stick open.

 

@Maverick H1L

As I rebuilt the 3.4, I used the method you described in your post, but I tightened them another quarter turn. So with the 3/4 turn I still have full 210 psi compression but no power. Timing is adjusted exactly on 10° before TDC. All ignition components are new except the plug wires. the secondary ignition voltage is OK on every plug wire (measured by an oscilloscope).

In my 3.4 engine new rebuilt cylinder heads are installed. I cleaned every pushrod before installation.

The more RPMs, the louder is the rattling noise.
Like I said, compression is very nice, engine has no power although it runs smooth.....When I step on the gas, there is something like a "delay" for 0.5 seconds so that the engine doesn`t act immediately when I step on the gas.

@Apeiron

I just want to use KED85's compression gauge method to ensure that I have the maximum compression on every cylinder, but though I have very good compression. So maybe the no-power-issue is something other.....

@ Dale

The problem is that I do have compression, but still rattling and a very noisy valves/pushrods and no power.....
So I don't think that any of the 12 valves sticks open.....


Greetings from Germany!
Flo

 

I can't see how a compression gauge could possibly tell you anything useful.

There are a few different methods to lash the valves while the engine is off. If your lash is messed up enough that all the rockers are clattering, you might want to pick one method and start over.

If you like, then after that you can "hot-lash" the valves while the engine is running.

 

yeah i dont understand why you would use a compression tester to set valve lash. the best way to do it is while the car is running. get them "roughly" set in while its not running then fine tune them. i made a set of junk yard valve covers with half the top cut of to help keep it semi-clean while the car was running and throwing oil every where.

 

Normally that's what I would advise, but if they're all clattering it can be difficult to listen for a change in the noise from a single rocker.

 

thats why you got to get them close to set with the car off. then tighten them an extra 1/2 turn. then start the car and tighten any that are clattering.(not to tight though!!!) then start with the first one and loosen till its clacking alot and slowly tighten till you cant hear it no more, then continue and move on to the next.

 

If you set them correctly with the engine off, then you don't need to do it again running, unless you really want to.

 

thats true, but I'm a perfectionist and like to fine tune them. Even if that means take off the intakes and all wires and fuel rail etc... and putting it back together again with the valve lash valve covers. just for 5 minutes and take it apart and do it all over again. but you can get them almost perfect with out the car running, just takes a little practice and patients.

 

OK, after some ideas I tried out that day, that didn't help, here's a little update:
I replaced the MAP sensor with another (used) one.

When I step on the gas pedal, the auto trans shifts into the 1st gear but the engine goes only to about 4500 RPMs almost without accelerating.
Like I said, timing is exactly adjusted. Vacuum lines are all new/repaired.
A new warranty-auto-trans was installed by a GM-Dealer!!! (no costs for me because warranty because they thought the car has no power because of the auto trans). TV-Cable is adjusted too.

What can this be?
I think when it's not the tranny the engine doesn't get enough gas or air to reach it's full max. RPM. I also drove withouth air filter and so on but it wasn't successful.....

Greetings from Germany!
Flo

 

I was refuring to if you set them with the engine off and to a compression gauge.

I once type the directions directly from the helms manual. It said 1.5 turns past lash, which most of us had confused at one time and though that meant spinning the pushrod. Its not, its vertical movement/slop. So if you adjusted it to 1/2 or 3/4. You could go another 1/2 turn easly.

 

@ Dale

So do you think that my valves won't stick open if I turn them 3/4+1/2 turn after zero lash? I can turn every rocker arm nut 1/2 turn further without setting every cylinder on TDC because the valves had been adjusted before, right? Remove valve covers - Turn every nut 1/2 turn further (1 1/4 turn total) - Install everything - Start - Drive - Be Happy? Like I said, the rattling is not my problem. My problem is the "slow", barely accelerating engine.

Do you think that there will be more power when I turn every rocker arm nut 1/2 turn further with the valve covers off?

Greetings from Germany!

Flo

 

You won't notice any significant difference in power with more preload, as long as you're not turning it so far that the valves hang open.

 

When the preload isn't the problem, what can it be?
I don't have a GM-OBD-Cable to connect it to my computer....
Maybe I would have to read out all the OBD-values at my next GM-Dealer....


Greetings from Germany!

Flo

 

I doubt you would notice much either. But you said it sounds like its rattling correct? If they are so loose its rattling, then you may gain something.

Did you check engine vac with compression? Maybe you have an intake leak somewhere, or some sensor is reading wrong, but not enough out to cause a SES light.

What exact setup are we working with here?

year? you said map so I assume 90-92
3.4 rebuilt
trans is rebuilt 700r4?
any other specs that may help

 

92 Firebird
rebuilt 3.4 engine (out of 4th gen 95 Firebird)
new rebuilt th700r4 tranny

The problem was also there with my old 3.1 engine
So now with my "new engine" and new tranny, there's no difference to the old drivetrain

I wasn`t able to the check engie vac with compression.

Maybe the rattling valves/pushrods are just the cause for the loss of power?
Before I installed new intake manifold gaskets on the old 3.1, everything was ok.
After adjusting valves and starting, there was a big loss of power, like now with the 3.4. But why is the tranny shifting up at about 4500 RPMs at kickdown?
Perhaps setting the rattling valves when the engine is running is the only solution???? I don't know.....

Greetings from Germany!

Flo

 

To me it sounds more like a tranny issue. But we will work on the engine.

If you go to adjust the valves while its running. Get an extra set of cheapie covers, and cut the top out and install them while running. For me anyway, when adjusting the valves oil was running off the side of the head and splashing onto the manifolds.

 

Because of the intake having to come off for adjustment, it's a pain to do running. I have always used a method similar to mentioned above. I spin the pushrods in my fingertips until they have the slighteset resistance, then tighten 1/2 to 5/8's more turns. Never failed thus far, and no noise.


Also if you have rattling of ANYTHING on the motor, you could be setting of KR (knock retard), where your engine is pulling ut timing because it has (or thinks it has) detonation, and would cause sluggish response, especially up hill.