[neo297]

I have experienced some highs and lows over the last couple of months. I blew the head gasket and had a bad exhaust valve. With the help of gigem75-Thank you so much!!- I was able to get the head to a local machine shop and had the valves redone and the head cleaned up. The only issue was the need to shave the skirts of the new shims as the shop shaved the valve stems pretty good, but all clearances were in spec.when finished. We tripple checked everthing and followed the awsome thread on head gasket change for dumies it was easy. We got to drive the car for a day then bang it died I could have died I was so pissed. Found out the timing chain masterlink broke/came off. I found all the pieces took the chain out and on inspection I saw what looked like a crack on the large intermediate shaft sprocket. When hand turning the motor the large sproket turns on the shaft. SOO now the head comes backoff I have a 2 bent valves out of 8 all other cylinders still hold water, no holes in the piston, moving good valves into the 2 bent ones seals well and there is no binding or play in the guides. I read a thread from earlier this year on broken intermidate shaft sprocket and saw a pic which showed a keyway. I thought maybe mine had broken.I removed the radiator, alternator, a/c(all under hood components as it looses freon anyway). I pulled the oil pan upper(as long as I had new motor mounts i took off the passenger side motor mount to access the one upper pan bolt that was a b***h to get to) and lower and removed the front cover to get to the sprockets. This was all done with the motor in car. I have some pics of the sprockets so y'all can see what I'm talking about. My question is, besides what the hell is wrong with me that I still want to and am enjoying doing all this work for a car that is only going to need more as time goes on, can I have the sprocket welded where it is cracked and how other than pressing does it work without a key? Where can I get a replacement shaft with sprockets if welding not an option? Pics are coming.

 

[neo297]

Here are pics. One thing if some were thinking I know my masterlink was on corectly in the right direction and clip seated properly I think it was removed previously and the clip may have been weak after finding all the parts the clip would not stay in the grooves it would pop off.

 

[neo297]

more pics of the sprockets

I hope you can see the cracks well notice no keyway

 

[Little Italian]

Never seen that happen before. Never heard of it either. How hard were your driving when it came apart? Got a spare bottom end? Having good chains and links is a major important thing. Needs to always be done right. Fix it right and never have a problem with it again.

 

[neo297]

Not fast or hard had just redone the head so we had started it let it warm up retorqued head then took it out for a ride just around the neighborhood it had stopped smoking was idling and running smooth. Never took it over 3000 rpm not over 35 mph. It was after I put on a new upper chain and retimed everything i went to turn the motor over by hand and only after getting the new chain on with tension on the sprockets I realized the large sprocket was turning but shaft and small sprockets were not, initialy without the cam chain hooked up the two sprockets would turn together so i thought it was ok. Then on further inspection saw the crack and pulled everything apart to fully evaluate. I now have no fear or apprehesion about doing the head work but the intermediate shaft problem has me worried as to how to fix or where to obtain a replacement. Getting everything off with motor in car was time consuming but not difficult.

 

[Andrew]

The big gear is I believe pressed onto the idler shaft with a key. It's not something you ever do at home, but occasionally these pieces do break. I think Gordon Raymond had a thread on this failure on the Engine forum some time ago.
That's a bad failure. Hard to know what happened unless the pulley just broke/separated from age, which there's not much you can do about. I have never had a timing chain link come undone, including on chains with no clip; typically the tension keeps it all together. Again, that's just my experience.
The grinding down of valves shims you mention suggests either the wrong shims, wrong or shaved valves, poor valve job in the past, poor assembly, or something.
Andrew

 

[neo297]

The big gear is I believe pressed onto the idler shaft with a key. It's not something you ever do at home, but occasionally these pieces do break. I think Gordon Raymond had a thread on this failure on the Engine forum some time ago.
That's a bad failure. Hard to know what happened unless the pulley just broke/separated from age, which there's not much you can do about. I have never had a timing chain link come undone, including on chains with no clip; typically the tension keeps it all together. Again, that's just my experience.
The grinding down of valves shims you mention suggests either the wrong shims, wrong or shaved valves, poor valve job in the past, poor assembly, or something.
Andrew

Looking into the large gear i see no groove for a key, at time of initial head repair I released and tightened the chain tensioner after putting the timing chain back on and checked there was no slop. I checked and rechecked the master link clip prior to buttoning everything up but the master link was broken when I fished it out, one pin was broken about one third up from the plate maybe the link broke rather than the clip coming off i would think the clip would be the culprit before a link failure. I agree with your assesment of a problem at time of valve job as all the valves were adjusted perfectly except for the one exhaust valve but the shop went ahead and cleaned up all the valve faces and seats and in doing so they shaved the top of the stems so all clearances were off after i rechecked them before putting it back on the car. I had to order new shims and then found they were resting on the keepers so needed to trim the skirts to make sure they rode on the actual valve strems. I searched and saw the old thread and it was mentioned that when the chain wraps around the lower intermediate sprocket it could lock it up and break the key/sprocket thats why i was inspecting closely and saw the crack and then pulled it all apart. I do not see any sign of a groove for a key in the shaft or in the lumen of the large sprocket but it does have three distinct cracks, I pulled the sprocket off of the shaft myself to inspect. Just was looking for confirmation that it should have a key or if simply pressed on could i have it welded and repressed on.

 

[vf31rhill]

If you want to stop throwing money at that engine, I have a complete never been into engine with 91,000 out of a 1988 Veloce. I drove it for 2 years before the car went down. Only known problem with this engine is leaking rear main seal, but now is the time to replace both crank seals and the oil pan gaskets anyway.

$700 for the engine and I can pallet ship to TX by UPS freight for $200. If the shipping is more than $200 I will eat the difference. This just food for thought.

Robert Hill in Memphis TN

 

[Little Italian]

I may have a extra timing gear out in my spares stash. I can check tomorrow. I also have a short block that I pulled out of my Spider last fall. I bent a valve on track day at the National Convention last year. Pulled the head for refubrishing. Set the short block aside. I have several engines so I know I'll never use it. Can make a good deal. PM me if interested. That would set you up with two engines potentially. A good thing if your going to be an Alfisti.

Oh... is there any damage to the hole in the front cover or the hole in the block where the gear fits. It's a big deal to align bore these.

 

[gigem75]

Sorry to hear about this, I know how much work you put into it. Definitly get a new/used intermediate gear. Also check the small bolt that we talked about that sets the cam timing gear on the cam. It can be put back together in the car but it's going to be hard to get everything as clean as it needs to be for a good reassembly, if it was me I'd go ahead and pull the motor. The ends of the shaft that turn in the front cover and block look pretty scored in the photo, they should be shiney, almost like oil starvation? A thousand bucks or close to it will buy you a lot of parts to do the job right and I wouldn't consider it throwing money at your motor.

 

[Elio Comello]

Roberts option is a good one IMHO. It is the one I would choose.

Elio

 

[Gordon Raymond]

I have seen this before. Many years ago, a friend did a DIY valve job on his Giulietta 1300 101 Normale. On reassembly, the upper chain was only 1/2 way on the intermediate sprocket. While warming up the engine, not driving, it went BANG! and stopped. He had me tear it down, and the remains were identical to yours.
I did another valve job, replaced the intermediate sprocket assembly, the upper and lower chain, (the lower had been stretched) the tensioner assembly, (marred teeth) and both cam sprockets. Reassembled, it ran quietly and smoothly.
I have seen other broken intermediate sprockets, usually in race engines. I have never broken one myself, but as these are cast, and can contain flaws, they can break.
Pictured is one that now lives inside a 1600 GTA engine, and is as light as I dared make it.

 

[144]

Don't try and repair the broken parts. Replace them.

 

[gigem75]

ah come on, you can get a couple more grams off that gear

going on the number one rule that it's usually the simple stuff I'm going with what Raymond said. A simple mistake we've all made at one time or the other.

 

[neo297]

Thank you all for your responses. Robert I will send you a PM after discussing it with my wife tonite. I was afraid of fixing it Versus replacing but had not seen enough posts to feel comfortable that simple replacement was an option.Little Italian I'll Pm you as well as I 'm finding out that you can not have too many spares. Thanks all
Paul

 

[Alfajay]

I have seen this before. Many years ago, a friend did a DIY valve job on his Giulietta 1300 101 Normale. On reassembly, the upper chain was only 1/2 way on the intermediate sprocket. While warming up the engine, not driving, it went BANG! and stopped. He had me tear it down, and the remains were identical to yours.

Gordon's wisdom doesn't need my humble confirmation, but I'll offer it anyways: Yes, that explanation seems plausible. In other words, the cracks in the intermediate sprocket assembly occurred as a result of the slipped chain and crunched valves. The failure of the sprocket wasn't the cause of the failure.

When you have a failure shortly after performing major work, the cause is far more likely to be the result of that work, than from some part just randomly failing. I strongly doubt that the intermediate sprocket assembly was already cracked, and just decided to let go immediately after the valve job.

But, regardless of the cause, the repair procedure is the same. As gigem75 suggests, "if it was me I'd go ahead and pull the motor". This will allow you to closely inspect the sprocket's bearing at the front of the block. I found that it is easier to do a quality reassembly job when the engine is on a stand and I am standing upright, rather than lying under the car with gasket sealant dripping on my face.

 

[neo297]

Gordon's wisdom doesn't need my humble confirmation, but I'll offer it anyways: Yes, that explanation seems plausible. In other words, the cracks in the intermediate sprocket assembly occurred as a result of the slipped chain and crunched valves. The failure of the sprocket wasn't the cause of the failure.

When you have a failure shortly after performing major work, the cause is far more likely to be the result of that work, than from some part just randomly failing. I strongly doubt that the intermediate sprocket assembly was already cracked, and just decided to let go immediately after the valve job.

But, regardless of the cause, the repair procedure is the same. As gigem75 suggests, "if it was me I'd go ahead and pull the motor". This will allow you to closely inspect the sprocket's bearing at the front of the block. I found that it is easier to do a quality reassembly job when the engine is on a stand and I am standing upright, rather than lying under the car with gasket sealant dripping on my face.

To clarify I do not think the gear let go first I definitely feel it was due to the masterlink failing and the chain coming off. I know the chain was on and tensioned I double and tripple checked the clip on the master link and to see the plates were in correctly. I had followed the head gasket replacement thread that had had the masterlink installed incorrectly so I was sure to check it. I did find that after collecting all the pieces that trying to get the clip on the link it would not stay in the groove it would pop off with minimal wiggling. Now I've been beating myself up over an $8.00 part that has now cost me so much more or I screwed up royaly but do not know exactly how so unsure how to avoid in the future other than just taking it slow and steady. But I have learned a lot about my motor in the process of taking it apart and now am that much more comfortable working on it. What do y'all think about the gear itself should it have a keyway groove or is it just pressed on?

 

[Gordon Raymond]

This makes analysis even easier. The master link is likely the weakest link on the upper chain, If the chain was 1/2 on the intermediate sprocket, and bound on a running engine, it would need to stretch. That will come from two places, the sprocket, and the link. The sprocket cracks, and the link then pulls apart. Boom!
I don't believe the link failure caused the sprocket failure. It is more probable the chain, not square with the intermediate sprocket, caused both failures. I have done some failure analysis on blown race engines (a l o n g time ago) for a major engine manufacturer. Components designed to last hundreds of thousands of miles, usually do so. Alfa Regina chains are right up there with the very best. Component failure is less common than human failure in almost every case. This is NOT a criticism. This is normal human failure. If in doubt, read the whole thread "fess up your mess up". I cannot be critical of errors in assembly that can happen to anyone. I ALWAYS sympathize with those that have suffered catastrophic engine failure. Posting your photo documented discussion will be a help to all Alfa BB readers.

 

[neo297]

This makes analysis even easier. The master link is likely the weakest link on the upper chain, If the chain was 1/2 on the intermediate sprocket, and bound on a running engine, it would need to stretch. That will come from two places, the sprocket, and the link. The sprocket cracks, and the link then pulls apart. Boom!
I don't believe the link failure caused the sprocket failure. It is more probable the chain, not square with the intermediate sprocket, caused both failures. I have done some failure analysis on blown race engines (a l o n g time ago) for a major engine manufacturer. Components designed to last hundreds of thousands of miles, usually do so. Alfa Regina chains are right up there with the very best. Component failure is less common than human failure in almost every case. This is NOT a criticism. This is normal human failure. If in doubt, read the whole thread "fess up your mess up". I cannot be critical of errors in assembly that can happen to anyone. I ALWAYS sympathize with those that have suffered catastrophic engine failure. Posting your photo documented discussion will be a help to all Alfa BB readers.

I want to thank all for their input! I do not take it as a personal attack. I wanted to hear from those more experienced than I as to what may have happened so I don't do it again this is the first car engine I have been into. I have had too many to count motorcycle engines apart and back together so I felt comfortable overall tackling what I did and followed the thread on my lap top out in my "garage". I am gratefull that this board has been here to help and those like gigem75 who is close enough and kind enough to offer personal assistance have. We all put ourselves outhere when things go wrong and it is frustrating that it ran for an hour or so, and well prior to going bang, that it teased me with what could have been. I'm going to go with roberts engine and keep mine for other spares. It should be easy to get out now that every thingelse is off of it!! I will keep you posted. I hope that others may review what happened and avoid similar issues with their projects. Thanks again.

 

[crashmctavish]

Those sprockets are not cast they are forgings. Do not weld them.