Valve timing question

[Carlspike]

I've got a 96 lumina with a 3100. It sounded like the valve timing was off so I took off the front cover and sure enough it was off. I took off the cam sprocket and found the camshaft alingment dowel had sheared off. I finally got it out and I'm putting it back together. My question is on the cam gear do you line up the hole with the timing mark on the dampener? There is a hole and another little mark, I think the other mark is just from the part being made but I want to be sure. My other question is does anybody know how much force the camshaft dowel pin holds and how much the center bolt on the camshaft sprocket holds? Thanks for the help.

[bszopi]

Not sure on the other question...

[Carlspike]

Well I got the car back together and timed it just like the picture showed. I even checked it three times to make sure it was right.... but the car still won't start. The original problem is the car stalled when I was driving and wouldn't restart. I got it towed to my house and checked a few things then decided to do a compression check. I did the front 3 cylinders and all of them read 0. I then had a friend verify that the valve train was moving. The crank sounds different than usual so I figured the valve timing was off, and when I took it apart it was off, but not much. I thought it had jumped time, but now I'm not sure if it was just slack in the chain. They were the original chain and sprockets so I replaced them anyway. As I said I got it back together today and it still won't start, it tries to fire a little more than previously but it still won't fire. The crank also sounds different than normal, it sounds like it's cranking slowly but the battery is fine. I'm going to do another compression check with a different gauge but other than that I'm lost. Anybody have an idea what direction I should take next?

[grandprixgtp_91]

you probably bent your valves, i saw this happen the other day at work on a new 3500, it sheared a pin and bent the valves.run another compression test and see if you have compression now, if not you got big problems, like i said , probably bent valves.

Jake

[Carlspike]

you probably bent your valves, i saw this happen the other day at work on a new 3500, it sheared a pin and bent the valves.run another compression test and see if you have compression now, if not you got big problems, like i said , probably bent valves.

Jake

I have taken that into consideration, but since the car was only a small amount out of time when I took it apart I'm not sure that the valves could be bent. It was only out of time about the amount of slack that was in the chain, maybe a half tooth at most. That wouldn't be enough to bend valves would it?

[grandprixgtp_91]

well that depends on how much the chain has stretched and how much the timing shifted , put the 2 together and you might have quite a bit of movement, when you ran a compression check and came up with zero compression , thats bad, thats really bad, if the valves are bent there not going to seat and causing a zero compression problem, just run another compression test, and if you have good compression then check spark, then check for fuel pressure, and then check to make sure your injectors are firing. u might have a blown fuse somewhere, or a bad cam sensor. or did you un hook your battery? maybe the cam sensor dected that the timing was off and shut the engine off, maybe unhooking the battery will reset the ecm and let it start. check those things out and go from there.

Jake

[Carlspike]

Just did a compression check and still nothing on the front 3 cylinders, so I didn't bother to go any farther. Looks like I did bend the valves afterall. It looks to me like when the alingment dowel broke the cam sprocket spun (due to the gouging marks on the mating surface) and that probably is what did it. It must have just stopped almost back in time. Tomorrow I'm gonna try blowing air in the spark plug hole and see where it comes out. Is there any other way I can check for bent valves without disassembly?

[grandprixgtp_91]

well you could pull off the front valve cover and take off one of the springs and move the valve around to see if it feels like its binding, it it does then its bent, or pull off the lower intake and look inside the ports, you should be able to see the valves and if there bent you should see it, just shine a flashlight in the sparkplug hole and if you see light through the valve seat then its bent. either way, if you got no compression you need to take the engine apart anyways.

Jake

[Carlspike]

I'm still deciding if I want to fix it or not, but if I do does anybody know where I could get a cheap used engine?

[Carlspike]

Ok. I've decided it might be worth it to do the heads and get the valves replaced. The only problem is that in the process of getting the cam dowel out the outside edge of the hole got rounded out a little bitter than the end. When I stuck the new dowel in it fit but it was kind of loose, only the back 1/2 to 1/4 of the hole seems to be holding it. So I filled the hole with JB weld and stuck the pin in there. I made the sure cam sprocket would still line up properly and I let it sit a day. The next day I put the timing back together. The book says the cam sprocket should only be 18 foot pounds, I cranked it down well past that to make sure it would stay. So my question is: How much pressure does a cam dowel hold? I cranked that bold down pretty good, but I don't want to do the heads and then have my dowel break again and ruin everything again. Any help would be great, thanks.

[ignoreance]

This Is the dowel pin on the camshaft??? If you wanted you could over size it to I think the chevy V8's bigger but it may be better to just buy a different camshaft. Is there some reason you want to hold on to the camshaft you have now ???


When you retorque a bolt you do want to torque it at a higher rate but usally not to much beyond specs usally about 3lbs the reason is the threds stretch... At some point if you have over stressed/stretched the threds to much the bolt will have a tendency to keep coming loose. Which makes for fun maintence again. Also though it doesn't say it your not going to hurt anything but putting a dot or two of Lock tight on it. You don't take it on and off so those bolts are better off locked down.

Also pending on how old your timing chain is it might be a good idea to replace that as well your in there. Check the things that need to be checked.... Just know when something goes like that you might as well check the other things around it.. what made it do that

Millage? Age of engine? How hard do you beat on it ? How hard did previous owners beat on it? How often was it run low on oil? did the timing chain stretch?

Those are questions you have to ask yourself.

If it takes a couple of extra bucks now its better than doing it twice and having it cost you time the second time cus you skimped out on it.