Required_Field

I found this YouTube video illustrating the valve drop method of finding top dead center. While it's helpful, I think he found TDC on the exhaust stroke. I don't have a YT account, so can't comment on it or ask questions, but someone who does might want to.


He starts by finding valve overlap on #1, which is near TDC on the exhaust stroke. He marks the damper, then rotates the engine, stopping before he reaches that mark, and measures valve drop before and after that mark. That's why I think he's getting TDC on the wrong stroke.

I would think you could start at overlap, but then continue FORWARD (clockwise from the front) till the intake valve closes (bottom of intake stroke), drop the exhaust valve, continue forward slowly till you measure contact. Mark the damper, Reset the exhaust valve, continue forward a ways (if you go as far as the exhaust valve opening, that's too far), drop the valve again, rotate backwards slowly till you measure contact, mark the damper and find the midpoint between the two marks. Reset the exhaust valve and rotate the engine to the midpoint. That should be TDC on the compression stroke, which is what we are looking for.

Or have I missed something? Sometimes things are too simple to see them straight ...

AlpineRAM

TDC is TDC- if you want to mark it on the flywheel or the harmonic balancer you can look for the TDC after the compression stroke or after the exhaust stroke- it really does not matter.

For adjusting the valves or the injection timing you will then need to find the correct TDC, meaning the one where the camshaft is in the correct position for what you want to do. (So basically every other TDC is the "right one") - this is because the camshaft rotates at exactly half the speed of the crankshaft.

Required_Field

Yes, I suppose it is relative to one's purpose, but I thought that one only needs the accuracy of the valve drop method for timing. Assuming the timing pin is not working or one does not want to use it for some reason.

AlpineRAM

Well, you use the valve drop on the TDC of the exhaust stroke and marks it on the harmonic damper.
Then, after rotating the crank another 360 degrees he's ready for timing it.

(Or you could also do valve drop on #6, then you are at compression TDC for #1 )

For timing I use my own marks obtained either by valve drop or made during a rebuild instead of the pin.
I found the pin to sometimes be some crankshaft degrees off, nothing to worry about when doing valve lash, but IMO not acceptable for timing.
I use the engine barring tool and normally mark the flywheel or flex plate in the lowest position for the autos- just remove the small dustshield and align the mark on the starter gear with the notch you filed into the AT bellhousing.

Required_Field

There it is! The thing too simple for me to see -- just rotate it another 360*, which he actually does in the video ... yep.

I just came in from doing this, I used the compression stroke, dropping #1 exhaust, and making marks on the bottom of the damper. I'd be interested in an analysis of the uncertainty in this method. Just guessing my uncertainty is at least a degree, more likely 2-3 degrees, just like the timing pin.

My truck has the factory damper, which I believe is 8.25 inches in diameter. So I calculate about .072 inches per degree along the circumference. The distance between my two marks was 2.13 +/- .05" measurement error, or about 29.5*. But given uncertainty in aligning both marks to the same referent, thickness of marks, etc., I'm not sure what to think. And I'm removing the IP, so I'd like to be more precise if possible.

It would be reassuring if the timing pin would drop in somewhere in that vicinity, but I can't get it to move in and out at all. I feel a little side-to-side play in it, nothing more. Tried tapping on it with a socket but still no play.

Since I have to figure out this T-bar puller and where I can get 8mm x 1.24 bolts, (I can get 8 x 1.25 ...???) I have some time.

gorms

I guess I'm a hack because I pin time it, but it works pretty good imo. Pull the PUMP timing plug and bar the motor slowly until you see the reference arm in the hole, closest to center as possible. Then pull the cam (engine) timing plug and feel for the notch with your finger. Should be close, slowly rotate motor until plug seats all the way into both in cam gear. If the timing plug on the pump falls right in the truck is stock timed, assuming the pump has not been altered.

If you are pulling the pump to do other work, make sure you don't rotate the motor while the pump is off to make sure it doesn't go back 180 deg out of time.

For the 8mm bolts, I am assuming you need them to pull the pump gear off. Intake horn bolts work great.

Required_Field

Thanks, gorms, I didn't think about the pump timing plug. I could work harder on the engine timing pin I guess and see if I can get it out.
The FSM said 8mm x 1.24 bolts for pulling the pump gear, and I don't know if such things exist or if that's just a typo. I tried an 8 x 1.25 in the pump gear and it seemed to thread just fine. I just need to come up with a puller now -- it looks like the puller should press against the end of the pump shaft, rather than the timing cover, while the bolts draw the gear outward on the shaft. Have to see what I've got that might work.

Required_Field

I got the timing pin working somewhat, but it is sticky enough not to be very helpful. There is pretty good agreement between my mark on the damper from the valve drop method, the pin when it works, and the pump timing tooth being centered. Guess we'll call it good. Oh, and for anyone doing it this way, you need something to catch the oil if you pull the pump plug.
I pulled the gear off the pump shaft using a couple old allen head 8mm x 1.25 Jetta TDI damper bolts, and the adapter for a slide hammer 3-jaw puller, used as a sloppy but adequate t-bar puller. I got creative with some u-joints, wobble extensions and magnet, and removed the two inside pump-to-cover nuts, loosened all the others. Ran out of daylight, but hope to extract the pump tomorrow.

rebar

Will this base work, or screw in the block, since I already have a dial indicator? Thanks!

https://www.harborfreight.com/multi-...ent-63663.html

gorms

Those blocks are hard to use for timing.
An oil drain plug threads right into the DV holder and is readily available at most parts stores (sometimes with an old one for a sample). Drill a 1/4" hole or whatever size needed to hold the indicator and drill/tap a set screw near the top to hold it.

rebar

Delivery Valve holder? Were measuring the exhaust valve deflection.

What I meant to ask was, Ive read if you unscrew the pole from the magnetic base on the one from Harbor Freight, it has a metric threaded end that is the same as the top of the pedestal where the valve cover bolts on like in the video. Or so Ive read..

gorms

Ah thought you were going towards injector pump timing....

rebar

No, Not quite yet.. I'm not convinced that my 13.5 isn't optimal for 2000 rpm cruising. ? Plus Im concerned it could slip.

A little closer to that kdp..