: Timing chain on rear bank has may have too much play...



jimsbox
10-27-10, 01:37 PM
I replaced my head gaskets and studded this engine and I noticed that the rear head timing chain goes a little limp I'd say maybe once per revolution by hand. It seems to be about 3/8 to 1/2 inch between the exhaust and intake sprockets and if run it with the starter it is apparent for a few revs then the oil pumps up the tensioner and it stops until you stop cranking it. It then soon bleeds off the pressure and goes back to having "loose spot". It is not loose enough to jump a tooth and the ratchet is working on the tensioner, I even tried a new tensioner and it pretty much does the same thing. It appears it is not quite enough play to extend the tensioner shaft to the next tooth so the valve springs force the exhaust cam to relax back in this one spot. The rest of the time it seems to be normal (meaning any rotational position but that one). Also, the tensioner is only extended and latched to the first or second tooth, you cannot collapse it all the way without un latching the ratchet so the tensioner is not collapsing. I need to get this engine together so please help.

Submariner409
10-27-10, 01:54 PM
You should be OK - I just stuck a long screwdriver down in the chaincase of my 2002 (oil fill hole, exhaust cam "tight" run) and it's a tad floppy. (Just did it again - car has been sitting since yesterday PM - "floppy" is a poor term - "slightly movable" might be better.)

Check against this diagram - the chains do have some normal slack. Oil pressure drops at engine:OFF and they will slack off..............

jimsbox
10-27-10, 02:23 PM
Thanks Sub,

My slack is actually in the short run between the exhaust and intake cams and there is not a similar loss of tension on the front head. I think you are right though, the tensioner is only out one or two notches so still nearly compressed, it cannot be compressed all the way without releasing the ratchet and it pumps up so I don't think the chain is stretched, or the tensioner is bad, but rather just not quite loose enough to go to the next tooth on the tensioner which will probably decrease the amplitude of the soft spot. I will wait til I give you and others a chance to reply or chime in and then reassemble and see how it goes. Also, the tensioner does spring out and reduce slack when pull the pin locking the ratchet.

Thanks again, you help as always is very much appreciated.

Jim

Submariner409
10-27-10, 02:33 PM
Apparently you still have the front cover off. The engine takes 17 revolutions (from initial timing setup) before the marks all align again: what's the short run chain status with all 6 marks aligned ?

Hint: Before you button up the timing cover, use a judicious amount of GM EOS (Engine Oil Supplement) or equivalent to pre-lube the chains and sprockets.

jimsbox
10-27-10, 02:43 PM
Sub,

I also noticed my manual says to torque the balancer bolt to 37 ft/lbs then 150 degrees but everything I read here says 120 degrees. When I get past about 120 to 130 it gets extrordinarily hard to turn, had to use a 650 ft/lb impact wrench to get it to 150 degrees. Could you check you manual and see if the torque was upped to 150 degrees or if it is a misprint in the '00 manual? I had the the pulley and front cover back on when I discovered the soft spot on the chain. I will check it at TDC and see if that is the soft spot and get back to you in a few. Also, do you think reusing the balancer bolt more than once is wise?

Submariner409
10-27-10, 02:53 PM
2002 manual and ALLDATA: 37 ft/lb + 120 degrees.

If the balancer bolt looks healthy, no reason not to use it if time is of the essence. For the ultimate in peace of mind I would, personally, get a new one. (BUT, some of those balancer bolts I have used on Olds 455's were pretty gnarly...........)

jimsbox
10-27-10, 03:08 PM
OK,
I just hand turned the crank to TDC and the loose spot in the short run is there and it is about 1/2 inch. You cannot force it to skip a tooth even with that amount of slop. I also noticed for the first time some slack, maybe 1/16th and certainly no more thanj 1/8th inch on the long run between the intake sprocket and the primary sprocket down below, measured about mid point of the run. I was able to put a wrench on the intake sprocket and turned it slightly moving the slack from the long run to the short run and that is when I have about 1/2 inch of slop. Please note the tensioner is on the Exhaust to primary run of the chain and the intake to primary run is the fixed guide. I did slop a lot of white assembly grease on the chains and hand turned them at least a full revolution when I first reinstalled the heads and sprockets so I think the guides and sprockets are well lubed. I did not lube the pressure feet (plastic shoe) on the tensioners, do you think I should remove them and do that?

Looks like 37 ft/lbs plus 120 degrees it is.

Thanks

Submariner409
10-27-10, 03:18 PM
You're good to go - button it up.

jimsbox
10-27-10, 04:08 PM
Thanks Sub,

For the benefit of others that will surely pass this way, I am going to offer a few suggestions I found helpful dealing with the timing system:

1)Remove the balancer and the timing cover.

2) Put the engine at TDC by reinstalling the balancer bolt and turning it clockwise as you look at the balancer until the primary spockets marks are both pointing to each other and the pins on the camshaft sprockets are both vertical to the head on each head. This may take several revolutions. It is really quite easy to do with a 3/8" ratchet with a 6 point 19mm socket if you pull the plugs first.

3)Remove one of the center camshaft bearing caps on each of the camshafts and put a long piece of paper about 3/4" wide between the camshaft and the bearing cap and resecure. Make sure it hangs out so you don't forget to remove them. This will lock the heads from moving from their TDC positions making reassembly much easier.

4)Before removing the sprockets or guides, use fingernail polish to mark the sprockets (exhaust and intake on both sides) and the chain so you KNOW you have not reinstalled incorrectly. Then use a tie wrap to secure the chain to the right bank intake sprocket (the exhaust has no holes because of the camshaft sensor ramps on the sprocket) and the left bank (looking from the flywheel end od the engine) exhaust sprocket. You have to remove one of the sprockets anyway on each head from the chain to get the head off. Then using long tie wraps secure the chain between the lower sprocket and the cam sprockets just above the lower sprocket so the chain cannot lose mesh with the sprocket. This will assure the timing is maintained when reassemble if you lock the flywheel at TDC.

5)Remove the chain guides per the manual after you removed the sprockets. Don't forget to retract and lock the tensioners (only the upper two, the lower primary chain should not have been disturbed)before reassembling.

6)When reassemble make sure the nailpolish marks line up. Put the sprocket on the chain then install it onto the camshaft.

jimsbox
10-27-10, 04:17 PM
Sub,
At TDC before I moved the slop from the long run I still had about 1/4 to 3/8" of play in the short run. I figure I am just dealing with the spring tension on the camshafts and that is removed by the hydraulic pressure created on the tensioners during cranking and running. If you agree then I will indeed button her up. I tried cranking it and the tensioners all move in and out under spring pressure as I would expect (no oil pressure of course because the balancer was off.) Let me know if you disagree with my suggestions on previous post so I can modify them if there are better ways to do it.

Thanks

Submariner409
10-27-10, 05:40 PM
Look straight at my chain diagram and visualize this:

The engine is running - the crank sprocket is turning the intermediate sprocket, thus loading the "straight side" of the chain - the "idle side" of the first chain will be slightly slack, and the tensioner will extend to keep the slack from flapping around.

This load is transferred equally to the bank cam drive chains in exactly the same scenario: the "straight side" - the tension side - of the chain pulls on the closest cam which takes out slop in the long run; the first cam pulled takes out the slop in the short run (at which point both cams are in time) and the slop is transferred to the slack side of the chain and the tensioner keeps that tight also.

Our cam drives are pretty quiet - early Ferraris and some other OHC chain drives had a spring-loaded cam drive tensioner and the "whizzzzzzzz" was most musical...............newer OHV guys try to duplicate the noise with Milodon or Cloyes gear drives.

stoveguyy
10-27-10, 08:03 PM
i asked this before but never got an answer. if timing mark on crank is at 12 oclock, the #1 cyl is at TDC, all timing marks should be straight up from heads. so turn crank 720 deg and all cam marks should be back at starting position. i think the point about 17 turns is not right. isn't it 7 turns?

jimsbox
10-27-10, 08:27 PM
As I understand it, you should go through all 4 strokes (intake, compression, power, then exhaust) in 2 full rotations of the crankshaft so 720 deg is correct. I believe that the value of 7 revolutions is what it takes to get the same links of the timing chain to realign if you had marked them first. I am not sure about 7 or 17 but it seemed to me that 7 is probably correct

Submariner409
10-27-10, 09:13 PM
Deleted..............too late to start counting teeth.

The 720 is correct - it's a 4 cycle engine - but somehow the oddball intermediate sprocket throws off the chain relationship.

Ranger
10-27-10, 10:03 PM
I seem to recall the old Guru mention 7 turns if memory serves me correctly.

stoveguyy
10-28-10, 01:44 PM
i wanted to pull a valve cover to check my timing marks after i did the heads. the cam sprockets will always be aligned or in sync. if the exhaust sprocket mark is at 12, the intake will also be at 12. i thought of cutting a little window into cover so i could see marks.

tateos
10-29-10, 07:48 PM
No offense, but how is this easier than the diagram in post #2? I have done a HG job, and I found the engine very easy to time and nearly impossible to screw up - the only thing I would say is use a square on the heads to make sure the marks are at 12:00 in relation to the head surface, and also, re-check the timing AFTER releasing the tensioners



Thanks Sub,

For the benefit of others that will surely pass this way, I am going to offer a few suggestions I found helpful dealing with the timing system:

1)Remove the balancer and the timing cover.

2) Put the engine at TDC by reinstalling the balancer bolt and turning it clockwise as you look at the balancer until the primary spockets marks are both pointing to each other and the pins on the camshaft sprockets are both vertical to the head on each head. This may take several revolutions. It is really quite easy to do with a 3/8" ratchet with a 6 point 19mm socket if you pull the plugs first.

3)Remove one of the center camshaft bearing caps on each of the camshafts and put a long piece of paper about 3/4" wide between the camshaft and the bearing cap and resecure. Make sure it hangs out so you don't forget to remove them. This will lock the heads from moving from their TDC positions making reassembly much easier.

4)Before removing the sprockets or guides, use fingernail polish to mark the sprockets (exhaust and intake on both sides) and the chain so you KNOW you have not reinstalled incorrectly. Then use a tie wrap to secure the chain to the right bank intake sprocket (the exhaust has no holes because of the camshaft sensor ramps on the sprocket) and the left bank (looking from the flywheel end od the engine) exhaust sprocket. You have to remove one of the sprockets anyway on each head from the chain to get the head off. Then using long tie wraps secure the chain between the lower sprocket and the cam sprockets just above the lower sprocket so the chain cannot lose mesh with the sprocket. This will assure the timing is maintained when reassemble if you lock the flywheel at TDC.

5)Remove the chain guides per the manual after you removed the sprockets. Don't forget to retract and lock the tensioners (only the upper two, the lower primary chain should not have been disturbed)before reassembling.

6)When reassemble make sure the nailpolish marks line up. Put the sprocket on the chain then install it onto the camshaft.

jimsbox
10-29-10, 08:27 PM
No offense taken, but if you miss one tooth because you are trying to hold tension on a springy camshaft while you put the chain on with your other hand while making sure you don't put some slack in between the wrong pulleys bad things can happen. This was not for an ego trip, I just spent a lot of time to make sure I didn't screw up something that I have never done before and it has been many years since I was this deep into a car engine. The way I did it makes it virtually impossible to mistime the engine but as I said, I still turn it through a couple of revolutions to be sure. I am sure you or other experienced mechanics could do any of the steps involved in a head gasket job much more efficiently than I can. I understand that as I am not a particularly experienced mechanic. I am assuming some folks that attempt this may have the same insecurities and inexperience I had and I was offering my insights but you know what they say...there's a thousand ways to skin a cat. By the way, thanks for your how-to posts, am using them as well as a few others as I go through this job.

Is Fountain Hills as hot in the summer as Phoenix? My dad lives in Tucson and it gets pretty toasty there but nothing like Phoenix in the summer time!

jimsbox
10-31-10, 02:58 AM
Tateos,


Did you have to do anything to make sure the steering wheel did not move when you disconnected the steering knuckle? It seems that I read somewhere there is an internal spring in the steering column that would be damaged or dislodged if the column is allowed to move with the steering box disconnected. Is there anything to that that you are aware of?