TheSamba.com :: View topic - Air flow meter (AFM) plug

Mon Nov 16, 2009 9:50 pm

Hard to say. The lifter is collapsed. Need to pull the rocker on that side and hold your finger at the top of the push rod while turning it to see if it is a bad cam lobe or just the lifer is leaking down. It the pushrod moves up and down then the lobe is good, there is just air in the lifter or a bad lifer or fill it with oil and bleed it again.

Mon Nov 16, 2009 10:08 pm

The air intake on both sides are going in/out at the same time. Shouldn't the valves open and close in order? Is it normal for two valves on one side of the engine to open and close at the same time?

Mon Nov 16, 2009 11:23 pm

Two opposing intakes will run on the same lobe on the cam, thus they can not open and close at the same time. I can not think of any circumstance that would make them do so, as it's hard to imagine that the cam could have been ground that whacky. An intake valve on one cylinder and an exhaust on another could open and close at pretty much the same time. I would hope that this is what you are seeing.

The two lifters on #1 sound like they aren't doing anything at all. Maybe there is dirt under the valve disc (the valve in the lifter itself) preventing the lifter from pumping up. They might have been reassembled wrong as well. :cry:

Tue Nov 17, 2009 12:17 am

We adjusted one of the rockers and now all of the valves are opening and closing. What we witnessed was the intake and exhaust valve opening and closing at the same time. Whew!

Another question - where exactly is the TDC mark on the pulley? We have two marks on ours. One is a slash (see below - Photo A). The other has three tick marks (see below - Photo B). Which one is correct? When Photo A is in line with the "0" on the timing scale, the rotor is pointing at the TDC mark, but when Photo B is in line with the "0" on the timing scale, the rotor is 90 degrees off of TDC (see Photo C). In Photo C the exhaust valve on cylinder #1 is closed (spring not compressed).

Photo A - slash, TDC?

Photo B - tick marks, TDC?

Photo C - When the middle tick mark on Photo B is at "O" on timing scale, rotor is 90 degrees off

Does any of this appear abnormal? If we are off by 90 degrees, can we just rotate the distributor accordingly? Do you still think something is wrong with the lifters in #1? They are brand new and never disassembled.

Tue Nov 17, 2009 12:25 am

we have a 1977 bay. On ours the mark is on the backside of the pulley. I painted it white to make it easy to see.

It MIGHT be here or somewhere like that.

Tue Nov 17, 2009 5:09 am

Find the notch on the fan pulley and line that up with the "O" on the timing scale and you will have found TDC.

From ratwell.... http://www.ratwell.com/technical/FindTimingMark.html

The notch on the distributor means little to nothing after all of these years and various distributors. If you need to see something there, use a magic marker to mark whatever number you want to see.

I would suggest that after you find the pulley notch for TDC and put a thin white line on it "l", you make a mark 180º from that "ll" to denote Bottom Dead Center for when you need to adjust the lifters on cyliners 2/4.

Sort of like this....

Tue Nov 17, 2009 8:41 am

Quote: I would suggest that after you find the pulley notch for TDC and put a thin white line on it "l", you make a mark 180º from that "ll" to denote Bottom Dead Center for when you need to adjust the lifters on cyliners 2/4.

In what sitution would we need to adjust the lifters? Did you mean adjust the valves?

I'm more concerned about the intake and exhaust valves opening and closing at the same time. If that is normal, I think we're okay mechanically, other than setting the timing which appears to be straightforward once I find the correct timing mark on the pulley. If our previous engine had a stuck valve, would that cause one of the rockers to bend at all? How often do the rockers need to be replaced/repaired?

Thanks!

Tue Nov 17, 2009 8:53 am

Adjusting the valves or lifters is essentially the same thing for you.

Solid lifters get adjusted about every 3,000 or so. Hydraulic lifters get adjusted about every 10-12,000 miles.

In doing valve or lifter adjustments you are essentially looking for things that are all of a sudden "different" and can alert you to a dropping valve seat or a tightening valve that may be an indication of an overheating problem.

Do both lines please. A model airplane paint brush and some white or silver paint works well on a nice black fan hub and will allow you to see the timing light.

Tue Nov 17, 2009 10:09 am

Thanks, that makes sense. I'm going to take a closer look at the timing this morning and will add the marks.

Tue Nov 17, 2009 12:02 pm

Found the TDC mark on my pulley! Ok, so with TDC on the pulley lined up with the "0" on the timing scale, my rotor is pointing towards cylinder 4 (90 degrees clockwise from the tick mark on the distributor). It looks almost exactly like Photo C above. What do I adjust to get the timing back on?

Tue Nov 17, 2009 1:03 pm

ziggybean wrote: Found the TDC mark on my pulley! Ok, so with TDC on the pulley lined up with the "0" on the timing scale, my rotor is pointing towards cylinder 4 (90 degrees clockwise from the tick mark on the distributor). It looks almost exactly like Photo C above. What do I adjust to get the timing back on?

If you are at the "0" mark you either have to be at TDC for #1 or #3. You can't be at #4. Go to Ratwell (or do a search) and find out how to verify when you are at TDC for #1.

Tue Nov 17, 2009 1:24 pm

I verified the timing mark with Ratwell's instructions. When the timing mark is at TDC (0 on timing scale), the rotor is pointing at #2 or #4. If it's at #2, I can rotate the pully 360 degrees so that it aligns again at 0 on the timing scale and it's at #4. I'm guessing that the distributor is in incorrectly?

Tue Nov 17, 2009 1:29 pm

Quote: I'm guessing that the distributor is in incorrectly?

go 1/2 turn (180 degrees) of the pulley and verify there is not another mark please. report back.

Tue Nov 17, 2009 1:47 pm

When you are at TDC on the timing scale, remove both valve covers. You will crawl under there and look at the valves for cylinder #3, while your lovely assistant moves the engine 2" on each side of TDC using a wrench on the alternator pulley.

If you are indeed at TDC for #1 cylinder, the valves from #3 will be tapping back and forth similar to my fingers after I have had 3 cups of coffee.

If you are at TDC for #3, the valves for #1 will be doing that as the engine moves back and forth before and after TDC about 2".

If you are indeed at TDC for #1, move the ignition wires on the distributor cap so that it is about to fire at that location, less the 7.5º of initial timing. Put a mark at the location on the cap with a sharpie to let you know just where #1 is to be located. Move all of the wires around the cap maintaining the correct firing order, 1-4-3-2.

Time with a real timing light to the specifciation.

Tue Nov 17, 2009 1:50 pm

There is nothing 180 degrees off of TDC other than the slash in Photo A above. That isn't even exactly 180 degrees off either. The only other mark on the pulley is the one in Photo B but I read on another forum (I believe it was Ratwell) that that was probably put in place by the PO

This is the mark I'm using as TDC because it's 42mm from the bolt on the side of the pulley.

Tue Nov 17, 2009 1:55 pm

Quote: When you are at TDC ont he timing scale, remove both vavle covers. You will crawl under there and look at the valves for cylinder #3, while your lovely assistant moves the engien 2" on each side of TDC using a wrench on the alternator pulley.

If you are indeed at TDC for #1 cylinder, the valves from #3 will be tapping back and forth similar to my fingers after I have had 3 cups of coffee.

If you are at TDC for #3, the valves for #1 will be doing that as the engine moves back and forth about 2".

That is a really good explanation - thank you! Unfortunately, my lovely assistant will not be home until this evening so it will need to wait.

This morning when I thought I had TDC, I rotated the wires with #1 towards the rotor, and moved the others accordingly but the bus backfired. I was mildly excited because the only noise I've heard from this bus so far is the sound of it cranking - the backfiring (while not an ideal noise) was kind of a welcome change. I immediately stopped trying to start it though in fear that I might mess something up in the engine.

Tue Nov 17, 2009 2:01 pm

Let me correct the spelling errors as we wait for the lovely assistant's return.

Tue Nov 17, 2009 4:45 pm

fyi -I am guessing you just took the shot where ever the pulley was.

If indeed the dist rotor is on solid and the key not broken, and this is a dual vacuum advance distributor and not an 009, then your options to fix it correctly have some risk to them. If the dist is an 009 I think that #1 is in a different location than a stock dist but someone who has an 009 correct me on this. If this is a stock dist and it points to #2, you might be better to just rotate the wires than pull the dist drive gear. If the washer under the drive gear drops then it is a bad news event and a moment of how well do you fish.

Tue Nov 17, 2009 8:19 pm

How do I tell what type of distributor I have? We haven't replaced it and it looks kind of old so I'm assuming it's stock.

Tue Nov 17, 2009 8:55 pm

ziggybean wrote: How do I tell what type of distributor I have? We haven't replaced it and it looks kind of old so I'm assuming it's stock.

Look for the numbers on the side and then go to Oldvolkshome.com to see what it originally fit and what the spec are supposed to be.