Question Regarding Timing (Cam Sprocket Location)

[IanDMacDonald]

So, Steve pointed-out that there is an index on the cam sprocket that must be pointing up when the dots on the cam bosses align with the cam cap indexes. Of course, I did not make sure of this. So, could this have bent valves, or is it just simply out of time, and I rotate the sprockets to correct?

[bikerphil]

It won't cause any damage running it like that, the timing will just be off a small amount, a couple degrees.

[IanDMacDonald]

So, I simply remove the cam caps (following the manual), and rotate the sprockets 180°?

[DiverRay]

IF you need to rotate one cam that much, pull the cam out, put the gear on properly, and re-install the cam/s with the engine on the proper mark. I'm at work, just leaving, so I don't have a manual handy to tell you the marks. I DO KNOW you do NOT want to rotate EITHER CAM in the head WITHOUT the crank rotating as well. IF the head is off, only rotate with ONE cam installed.
IF you are pulling the sprocket ONLY, then yes, loosen up the caps, pull the two 10mm bolts, spin the sprocket 180, re-install the bolts and bolt down the cam. Just make SURE nothing moved so everything stays lined up.

[IanDMacDonald]

Ray- Thinking about this, is there enough slack in the chain after removing the bridge and tensioner, and swap the sprockets 180° without loosening/removing cam caps? Otherwise, I'll just redo head installation ftom cam installation forward.

[crazy steve]

Yes, it's possible to rotate the cam sprockets without loosening the cam caps. But you'll need to take both sprockets off the cams, and MAKE SURE the chain is properly engaged at the crankshaft while reassembling. This definitely involves some fiddling around with all the loose parts, take your time....

[IanDMacDonald]

Right. NOT moving the cams is the objective. I find it odd that neither service manual mentions those marks. Do you know where you came across the fact that they're supposed to be on the same "side" as the dots?

[crazy steve]

I noticed the marks when I pulled the cams on one of my motors. Carefully looking at the pics in the service manual shows which way they go.

That's not the only thing not in the manual....

[IanDMacDonald]

Right. I'll take care of that in the morning tomorrow.

QUESTION: Can I wait till after removing both sets of cam sprocket bolts before removing the ACCT, or do I need to remove one set, rotate to "C", then rotate again and remove the other set?

I'd rather not move the crank without tension on the cam chain. If I remove tension AFTER I'm all done moving the crank, I figure it's less likely that the chain comes off the crank sprocket.

[TopCatGr58]

Hey Ian,

Leave the ACCT in place until you get both sets of sprocket bolts loose/off. When you pull the sprockets and allow slack in the chain, the ACCT will probably ratchet inwards trying to take up any slack, and then the chain will be TOO TIGHT/SHORT to be able put the repositioned sprockets and chain back onto the camshafts. Remember, rotate the cams so that the alignment dots are down UNDER for the 1st set of cam sprocket bolts, that way when you rotate to gain access the other bolts, you can then have the cams alignment dots pointing UP to help ensure that you maintain the cam timing when you reposition the chain/sprockets and put them back onto the cams. At this position, the crank pointer should be at the "T" mark for the cam dots. The "C" mark is/was only for doing the CCT adjustment.

USE a bungy cord or such to keep tension on the cam chain while you work on the sprockets, and while you're putting the sprockets and then chain back onto them. MAINTAIN this tension to keep the chain on the crank sprocket, and THEN reinstall the ACCT tensioner(should have recompressed the plunger) and then once it's installed, allowing the chain slack will then allow the ACCT to take up what slack there is at the "T" position. THEN as you slowly HAND turn the crank and cams around a couple of rotations, as the crank reaches the "C" mark the ACCT should be able to take up the maximum slack that occurs. Then reposition to the "T" mark and ensure that the cam alignment dots are still on point!

T.C.

[IanDMacDonald]

Update

So, I found a free hour before dinner to pull the sprockets. Someway, somehow, not only did I have them upside-down, but backwards as-well. So, I pulled the cams again, and turned the sprockets around, and made sure the marks on the sprockets matched the holes on the cam bosses. I pinched the chain between the galley and sprocket, so I had to remove the exhaust cam again to free the chain. Lesson learned. Dots line-up after many revolutions by hand. Checked valve clearances, and they're all the same as they were after I re-shimmed the valves a few weeks ago. So, no bent valves. A great relief confirmed by a compression check, although the #1 cylinder does not show much more than 100 psi. Worries me just a bit. Bent valves was my major concern.

So, looking those sprockets over, I obviously would not question Steve on his write-up of the sprockets (as those marks have to be of some significance, why else have the marks), but the question begs to be asked: what is the significance of those sprocket marks? I see no difference in the sprocket, whether it's upside down, or those marks matching the dots on the cam bosses. The teeth are all the same, spaced equally apart. Anybody have any insight to those marks?

[3Phase]

Ian,

From what I've been able to tell, it doesn't matter but I could have been totally wrong when I degree'd the cams.

The factory manual shows how to install the sprockets.


CCT Conversion (page 4)


Even if it's purely cosmetic do you want to be like that guy that puts washers on backward or upside down, then has to mumble defensively about his workmanship when someone notices? Don't be that guy, put the wash... sprockets on the way they're shown in the factory service manual.

.

[BillyRok]

I've installed an ACCT on three motors while shimming valves, two had about 30k on them and one about 17k, and all three had the sprockets 180 degrees off from the picture Scott posted -- the bolt hole with the index mark was down when the dot on the cam boss was up and lined up with the arrow on the bearing cap. There's no way to know whether somebody in the past had all three apart and reinstalled the sprockets upside down or whether the factory did it. If all 6 sprockets had been randomly reinstalled by somebody who didn't realize there was a "right and wrong" way to do it, that's 6 events with a 50/50 chance each meaning odds are only 1 in 64 that I would have found what I did...kinda like flipping a coin and getting heads 6 straight times I guess. Is it possible to hold the two sprockets in your hand one on top of the other and see a difference in how the teeth line up that way compared to rotating one of them a half turn? Maybe somebody with spare parts laying around could check?

Seems it can be a bit tricky to get the cams bolted back down without them wanting to rotate slightly as valves on #3 or 4 are open a little when the dots are lined up with the marks and the crank on "T". Last time I did it I had to get the sprockets back into position on the shoulders of the cam, no bolts in the holes yet, and then put an open end wrench on the hex casting of the cam near #2 (is that why it's there?) and turn it slightly to get the dots lined up. If I'm lucky the bolt holes in the sprocket and cam now line up. If not, then I have to jump the chain a tooth on the sprocket(s) and spin them to get things lined up before putting in the bolts and then installing the ACCT. Finally the fun part, nervously and slowly turning the crank to make sure everything is good. Still wish my motion pro tool wasn't garbage!

[mack]

Cams

NEVER, NEVER rotate the cams once the sprockets are in place without installing the CCT first!!!!!!!!!!!!!!!!

[IanDMacDonald]

Seems it can be a bit tricky to get the cams bolted back down without them wanting to rotate slightly as valves on #3 or 4 are open a little when the dots are lined up with the marks and the crank on "T". Last time I did it I had to get the sprockets back into position on the shoulders of the cam, no bolts in the holes yet, and then put an open end wrench on the hex casting of the cam near #2 (is that why it's there?) and turn it slightly to get the dots lined up. If I'm lucky the bolt holes in the sprocket and cam now line up. If not, then I have to jump the chain a tooth on the sprocket(s) and spin them to get things lined up before putting in the bolts and then installing the ACCT. Finally the fun part, nervously and slowly turning the crank to make sure everything is good. Still wish my motion pro tool wasn't garbage!

You don't/can't bolt the cams down with the dots straight-up, due to what you said: it forces the valves open. So, you follow the manual and get them close, then bolt them down. You then use a 22mm wrench and rotate each cam independent of each other to line the dots up. At that point, you pull the slack out of the chain off the crank sprocket, and bolt the cam sprockets in one at a time, starting with the intake. I then install the ACCT/Cam. bridge, and rotate the crank 180°, and then install the second set of nuts. Torque to 184 in. lbs.