Why do I always get the weirdos?

I pulled the cam gear back off today and swapped to the 5* key, installed the opposite way from the previous attempt with the 2* key. But no matter which key or what way I install it I keep getting 2 to 2 1/2* at the crank, lining up the cam mark with the mark on the front cam tower. It never changes and I'm sure I'm VERY close to the same alignment on the cam marks. If I was 1* off I could understand it but it NEVER CHANGES!!!!

I just pulled the thrust washer with the cam alignment mark on it thinking that I might have messed up the keyway in the washer but it looks perfect.

So WTF??!!

Any input will be more than I have at this point.

Dan

How are you checking it? If not using a dial indicator, valve lift method it's not uncommon to check the timing three times and get three different results.

Which way did you put the offset key in? To 'advance' the cam the key should be offset to the left as viewed looking down at it when it's on the cam.

I'm aligning the cam marks. I've rolled the engine over and realigned the marks several times and I get the same results. I want to retard the cam for performance (hopefully) so I put the key in to the right, which I thought was correct to retard it and you've backed up my understanding of it.

The only thing I can think of is that not having the oil pressure on the tensioner might have an effect but that doesn't really make sense because the chain from the crank to the cam is on the non-tensioner side of the engine and shouldn't change with the position of the tensioner (that section of the chain is tight).

So it sounds like I have the key in the right place but I still get the same, unchanging result. Maybe I should fire up the dial indicator just to double check.

Dan

Do NOT turn the engine ccw! I'm sure you know that already but...

Why would you want to retard the cam timing? That already takes place with TC enlongation.

Just roll a new IWIS chain in and be done with it. That puts everything, including IP timing, back (close) to where it should be.

It's a performance trick. You trade some bottom end response (I have plenty of that) for increased top end power, which is where I need it. I HAD the factory stuff right up to snuff - now I'm trying adjustments to see if I can get more out of it. I'll advance the IP timing 'till it knocks and back that off a tad and I have Greazzer's performance fuel pressure spring. Things to try.

I did the FSM method and came up with 10* BTDC. Going online to look to see if that's a good thing or not.

Dan

My thinking is, by retarding the cam you'll move the torque peak into the rpm area where this engine has a hard time breathing.

It will be interesting to see what happens...

Even more weird. According to the FSM I'm pretty much right on the stock timing - even though I started out there and it has a 5* (10 at the crank) key in it.

I'm SO confused!!!!!

Dan

Okey-Dokey. More research shows that I'm currently at 10* BEFORE TDC and specs are 9* AFTER TDC, so my offset key did, indeed, move the cam. I'm thinking this is too much so I'll go back to the 2* key.

BTW - as an experiment, instead of adjusting the valve lash to zero I just slipped a 0.004" feeler gage in there, taking the lash to zero - no adjustment required. Tomorrow, just to verify, I'll try the zero lash adjustment but I'll bet it'll come out the same. Just a lot simpler and you don't have to mess with the valve lash. (Probably ought to run the valves again anyway - lots of high speed operation since the last time).

Dan

Round 3 (or 4 or....)

First of all, using a feeler instead of adjusting the valve lash gives the same results, +/- a tiny bit (within the ability to read the equipment). Lots easier to slide a feeler in there.

Second, I pulled the 5* key (10* at the crank and substituted the 2* key. Now I'm reading 13* BTDC instead of 10* BTDC. I wonder if my dampner is off a ton? I guess I should pull the glow plug and feel TDC - even if that method isn't perfect it should tell me if it's in the ballpark.

The other thing that's weird - the cam mark alignment method keeps turning up 2 to 3* regardless of the key that's in there. This makes NO sense at all.

Any ideas, insights? All input is welcome.

Dan

I'd suspect chain and sprocket wear. I would roll in a new chain, replace the tensioner spring and rail, cam sprocket and call it done.

Then, play with cam timing offset making passes each time and see what works best.

btw, You will need to pull the injector, GP and precombustion chamber to get to the top of the piston.

Your crank dampener isn't loose is it? If it's ever been off chances are it may need new dowels. Pretty common on the OM617.

Not sure on the dampner. I had a heck of a time reinstalling it and I thought I had it properly on the dowels. I can't move it by hand.

Today's plan is to reinstall the straight key and measure using the dial indicator method. If I'm 18ish degrees off I will have learned something and I'll move the chain a tooth. If it's about right then I'll see if I can determine if the TDC mark is correct, probably by pulling the GP, injector, and pre-chamber (haven't pulled one of those yet).

I'll see what I learn.......

Dan