"When is it a good time to adjust the valve/lifters? I have about 78,000 miles and am just starting to hear a faint clicking sound from the engine. Is this a sign for adjustment?"
Both engines that were installed in Fieros (2.5l 4 cyl. and the 2.8l V6) had hydraulic valve lifters. These are now almost universal in modern cars and there are a couple of things that owners must be aware of in connection with them.
Hydarulic valve lifters require very clean oil to function properly due to the very small internal clearances inside them.
Any oil contamination can either cause the lifter to stick or can cause the clearance to wear causing lost motion in the valve train and a small amount of noise.
I suspect that is your problem judging from the mileage and minor character of the noise.
Cars with the bucket and shim valve lash system do not have hydraulic lifters and they do need periodic adjustment to account for valve seat and shim wear. These adjustments are usually very infrequent and definitely require special tools which the home mechanic cannot usually justify buying since they are so infrequently needed.
Incidentally, most 4 stroke motorcycles use the same system and it works extremely well in high speed engines.
Your 78,000 miles is not an unreasonable life for hydraulic lifters - especially in an engine which has likely been revved-up a few times. I think that you should replace the set - or just live with the noise. As long as it isn't too instrusive no harm will occur for a substantial period of time if you just leave them alone.
I once knew a taxi driver who swore that any V8 engine would go 3-400,000 miles if you changed the oil regularly and put a new set of lifters in every 70-80,000 miles. He had been doing that for 30 years and it seemed to work well.
From: Dr. Peter Frise
The best thing to do is to either ignore the problem until it gets worse (like clicking hard all the time), or replace all of the lifters. The second option is much better and it isn't really a difficult or expensive job.
None of the parts are heavy or likely to be rusted and all of the work is done from above with no need to lift the car so you should be able to go at it in a day easily.
Valve lifters cost around $4-8 each and you need 8 of them [on a 4-cylinder] (1 for each valve for each cylinder) and a couple of gaskets - specifically the vavle cover gasket (sometimes called a rocker cover gasket) and the lifter gallery gasket. I would guess the parts will run you much less than $100.
There is no point at all in trying to figure out which one(s) are bad - just do them all - you'll never manage to pick out all of the bad ones anyway.
The lifters live in a row just below the intake manifold on the rear side of the engine (you probably need an intake manifold gasket as well since I am sure you'll need to take of the intake as well).
Here are the (approximate) steps to replacing the lifters:
|do them one at a time|
|they may be a bit sticky and take a bit of persuasion (many people
use a little wire hook);|
CAUTION - do not scratch anything in there - it is all precision machined surfaces.
It might clack for a few minutes until the lifters are completely filled and pumped up and then it should quiet down.
You should change the oil BEFORE going anywhere with the car - all sorts of shit can drop in when you are working on an engine like this.
From: Dr. Peter Frise
Sigh, I really hate to take issue with Brother Peter on filling lifters prior to assembly, but how do you do that, and, is it necessary?
First, let say that there are so many variables when it comes to the lifter issue and different ways to accomplish the same thing. One thing I learned over the years (and it didn't take long) is it's a waste of time rebuild or disassemble lifters. If they need to be dissassembled to clean; well, they're shot, toss 'em, they're cheap. A rule of thumb I use is if the engine's dirty inside, put in new lifters. If things are relatively clean inside and the bottoms are flat, I'll reuse them, all things being equal.
As to filling the lifter with oil, how do you do this? You can't just squirt it in the side hole. To me, as long as there is enough oil in the lifter, to prevent galling on start-up, thats enough as I'll explain. Skipping the theory of operation, the object is to compress the piston to the middle of its bore. This allows for wear compensation and fairly fast filling of an empty lifter for the life of the engine. In reality, the lifter piston can be placed anywhere in the bore and will work just fine. With the piston near the top, it takes longer to fill when bled down and will "tap" until it is full. With the piston at the bottom, you run the risk of the valve hanging open; thats why the center is the happy medium.
One of the problems I have with full lifters is that generally they won't compress easily (or at all) during the valve adjustment and that makes it hard to tell if its working properly, or is stuck. I feel more comfortible with a lifter that I can compress by pushing the rocker down just as I take out the slack in the valve train (zero lash). The lifter will fill and be tight when oil pressure comes up and automatically fills the lifter. It may clatter for a little while, but should be quiet within a few minuites. There is sufficient lift in the cam to open a valve enough to operate with a partially collapsed lifter.
If the lifter is full, there will be no compression you can feel when zero lash occurs and when you dial in the preload, the lifter will bleed-off (hopefully) and be quiet on start-up, properly set. If the lifter doesn't bleed-down, the valve will hang open, but as the engine cranks and begins to run, the lifter will self adjust. All this assumes a good lifter. This is why that if there is ANY doubt about the lifters "goodness", new ones should be installed. Then there's the rule that you shouldn't put new lifters on an old cam, because if the lifters are worn, its a good bet that the cam's worn also. This is true, but you can mix new and old if time and money are a factor. Just don't expect it to last.
I tighten 1 turn after zero lash. This is somewhat universal on GM's with adjustible lifters.
From: Tin Man