Valve Adjustment: TDC or not TDC?
 

I have a few questions for my adjustment RE-DO:

1) When the ignition rotor points to the notch, the pulley is not EXACTLY at TDC (and vice versa). Should I adjust Valve #1 when the pulley is at TDC or when the rotor is at the notch?
(I though that they BOTH were supposed to be at their marks at the SAME time).

2) When I turn the engine about 120 degrees then 240 degrees from TDC, I do see the pulley notches to tell me when to stop and adjust the corresponding valve. But when I get back to around TDC, there are TWO notches (I think the notch to the left is TDC). Which one do I use for Valve #4?

3) With either position for Valve #4 in question #2, the cam lobe is not in the correct position for the GO NO-GO method. It seems that the cam lobe is half-way between an open and closed position. Am I doing something wrong?

Thanks,

Brian

Brian,
When you adjust valves, the protocol is to start with number 1 at TDC COMPRESSION stroke.
It isn't super critical whether you are on Z1 perfectly or not.
But remember, Z1 can mean Compression or Crossover.
So you must first be sure you are at Compression for number 1.
Checking the rotor position is good. The rotor must be pointing at the notch for number 1 on the distributor.
To avoid mistakes check the rockers. BOTH rockers will have some kind of gap.
If one or both do not have a gap it is likely you are not at Z1 compression.
Keep this in mind as well. AT Z1 TDC, compression, the intake valve will have closed completely at 110 degrees before TDC and will continue to be closed for the next 470 degrees of crankshaft rotation.
The exhaust valve has been closed completely for 340 degrees before TDC and will remain closed until 114 degrees ATDC.
So, from over 100 degrees before top dead center to over 100 degrees after top dead center BOTH valves are COMPLETELY closed.
You can measure the gap between the swivel foot and valve accurately anywhere between 100 degrees before and 100 degrees after Z1 TDC Compression stroke.
At Z1 compression BOTH valves are closed and will have some kind of gap.
At the other Z1 (crossover) BOTH valves are slightly open and will be tight.
Z1 crossover is useful for timing the cams with a dial indicator.
It can not be used to set the gap at the swivel foot and valve.
Look at the rocker where it rides against the cam lobe, At Z1 compression neither the intake or exhaust lobe will be close.
At Z1 crossover both the exhaust lobe and the intake lobe will near the rocker.
The exhaust will be closing and the intake will be opening. Both will be open slightly.
Firing order is 1-6-2-4-3-5
Turning the crank clockwise 120 degrees from number 1 Z1 TDC to the next mark and you are ready to adjust 6.
120 degrees more and you are at number 2.
Then 120 degrees later you are at Z1 number 4 compression.
Number 3 comes up 120 degrees later, then number 5 is last 120 degrees later.
1-6-2-4-3-5.

Very well said Doug.

Thanks for the ignition troubleshooting BTW, she runs like a cat with spicy mustard in it's...

Donnie,

"she runs like a cat with spicy mustard in it's..."

Now that was well said.

gotta keep it clean!

I stole that from someone here on the board, could not remember who wrote it though...

I have trouble seeing the Z1 mark and it never looks like it is quite in the right place.

I use a screwdriver to feel the #1 piston coming up, and watch the rotor coming around to firing position. If the piston is at the top of its travel and the rotor is in firing position, that is TDC, is it not?

From #1 rotate the crank to bring the rotor to the next firing position, and adjust the next cylinder in the sequence.

I guess I'm the only one doing it this way.

Connect a remote starter switch to the solenoid, then bump the engine around until a rocker arm is on the heel of a cam lobe (the low point), then adjust that rocker. It doesn't matter if the piston is at TDC as long as the valve is completely closed. Repeat for the next rocker.

Or follow the distributor rotor and do it the traditional way. Same difference.

Sherwood

Sherwood,
You are exactly right.
For folks that are doing a valve adjusment for the first time, it works to go through the entire proper method.
Veterans will just jack up the left side and do whatever valves are on the heel of the cam, then rotate the engine until the remaining rockers are on the heel of the cam. Put the left side back together, then do the right side.
It's all about being familiar with the whole process.
Kind of like medical types, See, Do, Teach.

My $02 - I can be totally wrong here.

I think you trust the pully marks first, then the rotor and dist mark as a secondary reference. In other words, stop on the pully marks not the rotor reference mark. The rotor does not exactly line up with the dist mark at TDC, just roughly pointing at/toward it. The TDC C#1 mark is the second of the two that are close together. The other two are the TDC marks for the other cylinders.

Rusnak,

Thanks for your clarification. That's how I adjusted the valves the first time.

According to the above, it shouldn't matter too much (apparently there is some leeway so that I don't have to be exactly at the Z1 line).

I'm trying again tomorrow, possibly the old-fashioned way this time if I could reach in there.

Brian

+2 on what Sherwood said...Oh, and that's spelled "pulley"

Here is a method worth understanding. This works for any car, any number of cylinders or any configuration. This also works if you have no pulley marks or even no pulley or distributor! Also you can find TDC accurately, adjust your valves and set your distributor with no marks what so ever!
First, write down the firing order, but split it in half with the first half on top and the second on the bottom. Like this;
162
435

Now, with all the valve covers off rotate the engine and watch for the valves to overlap. When the intake and exhaust valves for a particular cylinder are at the perfect crossover point, (when they are both open the same amount,) then the cylinder that is OPPOSITE on the firing order is at TDC. In other words, number 4 is at crossover then number 1 is at TDC, number 2 at crossover then number 5 at TDC, etc.
Sounds a bit confusing, but it is really simple and works just as well on a V-8 or an in-line 4. Like I say, worth understanding for those times when you can't find timing marks or need to verify TDC. This principal has save my A$$ many, many times in the last 30 years of working as a mechanic.

Matt

Nine9six, I swear I'm an edumacated speller, I just can't type. I talk real good too. Hoping I don't end up in Irak.

I know you was an edumacated speller, cuz you spelt it rite, twice. I was jes messin with ya. We both keep talkin like this, you, me an John is all gonna wind up in Irak!:D

hahahahahaha!!!

I didn't see Brian's question 3 answered. Some pulley's do have two marks at TDC for 1/4. Use the one on the left. The one on the right is an advanced timing mark.

For someone who has never done this before but mechanically inclined, how long does the valve adj process take the first time? How long for for an experienced wrench?

Thanks!

Mark,
The time involved can vary depending upon how much equipment is removed to gain access to the valves.
Earlier cars without catalytic converters passing in front of the drivers side can be done in a couple hours. Especially if a lift is available.
Working on the ground with a car that hasn't been apart for several years can take up to 6 hours, plus more parts, exhaust gaskets, nuts and bolts, etc.
Careful inspection for head stud problems, leaking valve covers, resurfacing of valve covers, fixing leaky rocker shafts adds time.
Plus an oil change is usually part of the deal.
Of course once the car is in the air, a smart mechanic checks everything he can access. Brakes, wheel bearings, CV joints and boots, tires, hoses, loose wires, heating hoses, brake lines, throttle linkage, steering linkage, he might even do a little cleaning.
All part of why the good shops cost more.
I'd figure at least 4 hours for your first time.
It could run more depending on your car and available tools.
And how close is the parts house for that one last item.
For certain it will take an hour or 2 less the second time you crawl under.
I always put a quart of oil in the drivers seat to remind me to fill or top off the oil.
It's amazing what I forget once I'm interrupted with a call or "honey do".
I use a small 3'x4' piece of carpet to lay on. Lots of light and lots of rags. Big pan to catch the oil, even if I do the left side-right side method.
Nothing like fixing that little annoying tick, tick, tick.
Have fun,

Mark,

You are talking about the '87 911 right? A lot of people say to remove the catalytic converter to get access to the left exhaust valves. I choose to leave it on because it's not a problem and adds time to the job. You will have to remove the heater blower tube and remove some brackets for the spark plug wires so you can remove the ignition rotor, and the inner cap so you can see the notch in the distributor.

You should have 11 quarts of oil and new filter, the gasket kit, 4 feeler gauges, the valve adjust holder tool, a good work light. I start the night before by cleaning the entire underside and engine compartment with a pressure washer and Purple Power degreaser from Napa Auto. I let the engine dry off while I drain the oil. The next morning, with cold valves, I take off the valve covers and start with the procedure for finding TDC for cyl #1.

Some to the time consuming things: (1)Forget about using a mirror to find the gap to feed the feeler gauge into. Just loosen the lock nut, back out the adjuster screw enough so you can insert the feeler gauge by feel, then tighten it down. This tip alone is worth maybe a few hours for the first timer. Pull open the rocker by hand if it doesn't open. (2) You have to find the correct gap by fingertip feel, and develop a touch for the correct amount of drag against the feeler. (3)Have a new belt or a belt from a 911SC handy, if your pulley is worn, then you will have a hard time turning over the engine with the fan belt. (4)Once you take the feeler out, it is almost impossible to put it back in. Check and recheck it before taking the feeler out. (5)Have a pack of spare feeler blades handy. It is easy to break or bend them. (6)If the car is fighting you, slow way down and go grab a beer and watch some TV. Start again after collecting your thoughts.

Good luck!

Mark,
rusnak offered very good advice, however the "Back side method" as found in the Tech Info Center offers a quicker, accurate way to check and adjust your valves.
Notice rusnak recommended having several .1mm feeler blades on hand, since they are difficult to work with.
The backside method uses a common feeler obtained from any feeler gauge set. A .0025" Go and a .003" No Go.
The idea is first check the gap at the rocker arm and heel of the cam with a .003" No Go feeler.
No need to back off any screws, just attempt to slip the .003" No Go feeler into the gap. There's plenty of room and the radius of the cam and rocker arm simply lead the feeler into the proper position.
If the .003" feeler does not slip in and the .0025" Go feeler does slip in, that valve is set correctly with no need to make any adjustment.
The idea here is to check each valve before you make any adjustment.
Saves lots of time.
No need to have a special tool and extra blades.
If the .003" No Go feeler won't go the setting is not loose.
No more guess work over how did it "feel".
If the .0025" feeler slips in, the setting is not too tight.
The number 3 and 6 intakes up in the corners are easier to get to, since you slip the feeler into the rocker/cam gap.
Easy to get to and you can slip the feeler in as many times as you like with out readjusting.
Simpler and easy to check your accuracy before you button the motor up.
Read the article and feel free to ask questions.