Broke timing chain - How screwed am I?

D

Dr. Jeckel

New Member
Joined
Jul 29, 2003
Well I just got through spending the better part of three days changing my timing chain, water pump, adding an external oil cooler and swapping out valve springs on the car. Not to mention cleaning all the gunk off everything.
Good news was that the old cam gear was in perfect order.
Bad news is that after getting everything on and back together, I go to fire it up and it just cranks over. I thought the cam sensor was outta wack so I take the top off and start moving the balancer and the reluctor didn't move. I thought that can't be good so I pull it out and look inside the front cover and my brand new timing chain is broke. I thought I was about to have a breakdown.
What could have caused it to break? The heads and cam are stock and I put on comp valve springs. The timing chain and gears were replacement "cloyes" pieces from O'Reillys. It was REAL tight when I put it on, it took a little bit of effore to get it all on there.
My question is has anyone else had problems with these replacement chains and did I bend any valves when I was cranking it over? When I cranked the engine over it didn't sound like I hit any valves, my friend bent some on his Ls1 during a cam swap so I know what it sounds like.
Should I get another set from O'Reillys and see if it fits looser or get a replacement peice from Aggressive or some vendor?
I would like and need to get this done as soon as possible, but don't want one to break again or while I'm doing 100mph. Please, any help or advice is GREATLY appreciated.
Thanks, James.
 
James,

I agree with Neal. For the timing chain to break there must be some mechanical interference in the engine itself. Something along the line of piston to valve contact. Timing chains don't just break for no reason.

Neal
 
That's what it sounds like, improper installation. Guaranteed you bent some valves in the process too.

I remember when my 66 Chevelle broke a crank key while under a nitrous run at about 100 mph. Bent just about every valve. Amazing what a 30 cent part failure can do.
 
Well the thing is that I took the old gears and chain off and put the new ones right back on the same way. The only difference was that I had to tighten the bolts on the cam gear to get it to slide on, it was extremely tight. I don't see how there could have been interference in the engine since I installed it the EXACT same way as I took it off. I have been reading and from what I can tell I may not have bent valves. Is there anyone who knows definitely if I did or not? I guess the only to be sure is to do a compression test once all is back together.
 
Need more info. Explain the EXCACT procedure you used to install the new timing set. I don't want to tell you how to do it. I want you to tell us how you did it. That will explain everything. Just want to add that Neal is correct. There is no way it broke by itself, It must have mechanical interference to break and yes it was piston and valve contact. Tell us how you did it so we can show you were you went wrong. Sorry to say the heads are coming off.


Neal
 
Like I said. I took the timing cover and everything off. There was my perfect, but a little loose, timing chain and nice looking cam gear. So I unbolt the two bolts on the cam gear. I slide it, the timing chain and crank gear off. I did not move the cam or crank. I slid the new crank gear on, then with the timing chain on the cam gear I lined up the teeth&chain so that the bolt holes on the new cam gear line up with the holes on the cam. Therefore everything is still exactly setup as it was. The only difference is that the cam gear wouldn't slide onto the cam. So I started to bolts into the cam by hand and then tightened them down until it squeezed the cam gear onto the cam. The I installed the dampner, evcerything else and reinstalled the cam sensor as per the marks when I took it off. That is what I mean by I put it back on exactly as it came off. So how could a valve have hit a piston if the cam/crank relationship was exactly the same as before.
Can I check to see if i bent a valve by taking off the rocker arms so all valves are closed, then crank over the engine and look at my readings?
That should tell me if I have a bent valve if a cylinder is greatly less than another, correct?
Thanks for the help, James.
 
BINGO!! WE HAVE A WINNER!!

You did not install the gears in the same position even if you think you did. That is why it ws so tight and the bolts were so hard to get in.

You need to line up the dots. PERIOD!!!!

There is no way to install the set with out knowing EXCATLY where the crank and cam are in relation to each other. You must have the crank gear with the dot at 12 o'clock and the cam gear with the dot at 6 o'clock. You cannot do it the way you did as there in no correlation between the crank and cam that way. You installed it inccorectly sorry to say and you have had MASIVE piston to valve contact. Just think how much force it took to break the chain. That force was bewteen your valve and your pistons . The heads need to be taken off as I will give an almost 100% guarantee that you have hurt valves. I am sorry to be the bearer of such bad news but these are the facts. The chain was installed incorrectly . Now is your chance to send the heads out and since you will be buying valves you might as well have some work done to the heads such as port and polish and larger valves. This was an expensive way to learn how to install a timing set.

Neal
 
When I installed my cam in my LS1 I did it the exact same way as this. I took the timing chain and cam gear off, I marked where they were of course, then put them back on after putting in the cam, lining them up with the marks.
If I took the old chain/gears off and the cam didn't move and the crank didn't move. And I put the new peices back on without moving anything. I matched the cam gear back to the holes on the cam. I didn't rotate the cam to match up, I simply took one set off and put another set back on in its place. The holes only would have lined up if I had it correct. I'm sorry, but I don't understand how my cam/crank relationship would be off since I didn't move either one. I matched up the cam gear holes before putting the chain onto the crank.
Could the tightness of the chain when I put it on have caused any problems?
 
Believe me. It was not installed properly and either is the cam in your LS-1. VERY INACCURATE way to isntall a timing set. You have a loose chain and that right there gives a few degrees of offset, then you force it on more degrees. It was OFF ENOUGH AND THE VALVES TOOK A VERY HARD HIT!!!!. I am not trying to be a jerk but WHO SHOWED YOU HOW TO DO IT THAT WAY? they should be shot. There are only 2 ways to install a timing set and yours is not one of them, That is the most backwards thing I have ever heard of. Once again not trying to be a jerk but it was installed incorrecty PERIOD and so is the one in your other engine. Yes the other might run and run well but its not installed correctly. Get a KNOWLEDGEABLE real TECH to help you. Not just a friend that thinks he knows. I wish you were local I would help you out. I am a profesional engine builder by trade so i have the background to understand way things have gone wrong. I am very sorry to hear about your mishap but its hurt.

Neal
 
No one showed me. Just thought if nothing changed in the relationship then it should be ok. I can see what you're saying with the sloppy chain and it being off by a little bit. I guess these engines don't have as much play in the clearence as what some has said.
This sucks cause its my daily driver and I don't have any money to throw around cause I'm planning a wedding. My fiance is going to Love this one...."Honey, it looks like the honeymoon will be spent in the garage".
Is there a way to check how many I bent with a compression tester like I said before? I want to be absolutely 100% sure what I'm up against. That way I can decide a course of action.
Thanks again for setting me straight and the help. I will never again install a cam or timing chain without doing it BY THE BOOK.

Its funny how life lessons cost more as you get older.

I tell you what. You pay for shipping and you can have it. This thing is going to get me divorced before I'm married :D
 
Don't give up. I have been there before. The only real way to know how many you hurt is to get the heads off and check them all. You could properly install a new timing set and do compression tests to try and see which cylinders have trouble. If you want some technical advice now that we know what has happened feel free to email me and I will help you all I can. I was young too and learned a few things the hard way. I will walk you through all the steps to properly diagnose your problems and give you the correct way to resolve them. Congrats on getting married. I was your age when I did it myself. let me help . We will get you going again.

Neal
 
Don't give up!

Sorry to read such a thread, especially about your errors. But look at it this way, If done by yourself, you're only the broken valve and some gaskets away from getting your ride rolling. Probably the most expensive part is the valve and valve work from a machine shop. The rest would be just your labor of love to put her back together. Hope everything works out good and right for you.:cool:
 
bent valves

Musclecar Neal has given you some good advice. I would like to add to it. You can check for bent valves without removing the heads or installing a new timing set. Remove both valve covers. Remove both rocker arm shafts. This will take all of the tension off of the valves and (should) allow them to close. Beg , buy, or rent a compression gauge or (better) a leakdown gauge. Check each cylinder and see what you come up with. Unfortunately, I don't expect you to be happy with your findings. Good Luck!:eek:
 
Dr. Jeckel said:I don't see how there could have been interference in the engine since I installed it the EXACT same way as I took it off. I have been reading and from what I can tell I may not have bent valves. Is there anyone who knows definitely if I did or not?[/b]
Click to expand...
My latest experience with my timing chain proved that these are most definitely interference engines. :eek:

Thankfully, when it finally shredded, the car was just at an idle but it did bend three valves. Only one was bent enough to see it & the other two were revealed during a pressure check of the heads at the machine shop.

Also, don't be surprised to find out that 99.998% of the people you ask about purchasing/renting a leakdown tester haven't the slightest clue what you're talking about. I got the same blank stare at every auto store I asked at...even the one that actually carried a tester (hanging on the wall). :rolleyes:

Just save the money and effort and yank the heads. I'm sure you hurt some valves.
 
i just installed my new timing chain and gears a couple weeks ago...granted i haven't fired up the motor yet but i installed the gears "dot to dot" as they say...12 o clock on the crank gear and 6 oclock on the cam gear...the chain shouldn't have to be FORCED on...mine slid right on with very little force...it's tight but not ready to bust out tight...also make sure the engine is at TDC #1 when you install the timing chain and gears...you will know you are at TDC if either A. the crank gear dot is facing directly 12 oclock...or B. if you used the balancer timing mark and set it to 0 exactly BEFORE you pulled it off...then you are on TDC #1

also torque the cam bolts and tensioner to specs...use some loctite so the bolts never wedge out ever while the motor is running...
 
Just follow the stuff on gnttype.org and you will be fine. stick to one persons info and you will be fine. too many cooks ruin the soup. and rookie info will kill you everytime.
 
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