SII timing chain broke......

[6 BANGER]

I was justgetting my car back on the roadd and ready to tune and on simple acceleration my timing chain broke destroying the front cover, bending valves and marring the tops of the pistons. After a slow and meticulous disassembly we could not find any real reason for it to fail. Has anyone else had this happen to them, is there anything inparticular I should look for?? Any help would be appreciated.

 

[Squid4life]

What kind of timing chain were you running? How many miles? No other issues with cam or crank rotation? Man, that sucks, sorry to hear about it. What heads are you running, and how much spring pressure? Could that have played a part in it?

 

[mygn276]

Never had problems with the timing chain breaking, just had the keyway give out as there is not much holding the bottom sprocket in place. It bent valves and dinged the cam lobe. I was lucky i was only driving 20 MPH at the time it let go. My bigest fear is it breaking on a full blast down the track as that would make for a verybad day.

 

[LOT]

crank keyway

Never had problems with the timing chain breaking, just had the keyway give out as there is not much holding the bottom sprocket in place. It bent valves and dinged the cam lobe. I was lucky i was only driving 20 MPH at the time it let go. My bigest fear is it breaking on a full blast down the track as that would make for a verybad day.

Locator only--230 ft. lbs. of torque on the big bolt is what keeps it from moving.

 

[Squid4life]

Locator only--230 ft. lbs. of torque on the big bolt is what keeps it from moving.

Are you saying the crankshaft bolt holds the crank timing gear on and in place? Maybe I am missing something here but don't think that's the case. The crank gear is press/slip fit. The bolt holds the balancer/pulley on. If the bolt held the crank gear on it would tighten over the seal/front cover/oil slinger (if used), correct? Did I misread your post?

 

[BlownV6]

Are you saying the crankshaft bolt holds the crank timing gear on and in place? Maybe I am missing something here but don't think that's the case. The crank gear is press/slip fit. The bolt holds the balancer/pulley on. If the bolt held the crank gear on it would tighten over the seal/front cover/oil slinger (if used), correct? Did I misread your post?

240 ft# clamps that gear between the balancer hub and the crankshaft bearing buildup. If that bolt isnt tight then the clamping load on the gear is reduced and will lead to a keyway failure. Mike

 

[Squid4life]

240 ft# clamps that gear between the balancer hub and the crankshaft bearing buildup. If that bolt isnt tight then the clamping load on the gear is reduced and will lead to a keyway failure. Mike

Aha, clear as mud! Thanks Mike for clearing that up. I was trying to picture it in my head but it wasn't making sense. Been a little while since I have the motor apart to see that. My photographic memory is out of film. :biggrin:


EDIT: Jeez, talk about a "duh" moment... :redface:

 

[oldtimer]

QUOTE
I was justgetting my car back on the road and ready to tune and on simple acceleration my timing chain broke destroying the front cover, bending valves and marring the tops of the pistons. After a slow and meticulous disassembly we could not find any real reason for it to fail. Has anyone else had this happen to them, is there anything inparticular I should look for?? Any help would be appreciated.


Hey Mike,

Might be a good time to solicit another Danny Bee belt drive order. We talked in Reynolds about this and you (once again ) said that we need a minimum order of 10 sets. I want (need) one, Willard Brown wants one, I have a friend that wants another and maybe two sets. This is a start at least.

What ya think ?

George, in Alberta .... bbbrr it's cold up here right now

 

[BlownV6]

QUOTE
I was justgetting my car back on the road and ready to tune and on simple acceleration my timing chain broke destroying the front cover, bending valves and marring the tops of the pistons. After a slow and meticulous disassembly we could not find any real reason for it to fail. Has anyone else had this happen to them, is there anything inparticular I should look for?? Any help would be appreciated.


Hey Mike,

Might be a good time to solicit another Danny Bee belt drive order. We talked in Reynolds about this and you (once again ) said that we need a minimum order of 10 sets. I want (need) one, Willard Brown wants one, I have a friend that wants another and maybe two sets. This is a start at least.

What ya think ?

George, in Alberta .... bbbrr it's cold up here right now

I will start a thread tomorrow on this and see just how many are intrested. Mike

 

[Squid4life]

Dare I ask how much those Danny Bee's are for these motors? I guess "If you have to ask...".

EDIT: Nevermind, saw your new thread.

 

[Eticket]

have you checked the oil pump setup to make sure something didn't stop the gears? I could be wrong, but I think a local friend did this when something stopped up his duttweiler pump setup.

 

[6 BANGER]

Thnx for all the help.

I will check into the oiling system. Also could Squid4life elaborate more about the belt drive setup to a fellow swabby. IC2(SW) Nazaryk off the USS Spruance DD-963.

 

[gnxtc2]

Backside of front cover

Front cover

Belt drive

Belt drive

There is more needed to install a belt drive on the V6.

You are going to need:
- Remote water pump
- Remote oil pump (belt driven)
- Mandrel set up for individual belt drives (oil, alt and p/s if you have)
- Distributor set up (Jesel belt drive or dizzy modified by Mike Booher)

IMHO - the reason chains break is due to spring pressures and the sequence of the open/closing of the valves.

Billy T.
gnxtc2@aol.com

 

[Squid4life]

There is more needed to install a belt drive on the V6.

You are going to need:
- Remote water pump
- Remote oil pump (belt driven)
- Mandrel set up for individual belt drives (oil, alt and p/s if you have)
- Distributor set up (Jesel belt drive or dizzy modified by Mike Booher)

IMHO - the reason chains break is due to spring pressures and the sequence of the open/closing of the valves.

Billy, thanks for the pics and explanation. Wow, that thing is more like porn or jewelry than engine parts... :biggrin: Very nice. I, uh, think I will stick with a gear drive unless I win the lottery. A little much for my street car.

 

[Squid4life]

I will check into the oiling system. Also could Squid4life elaborate more about the belt drive setup to a fellow swabby. IC2(SW) Nazaryk off the USS Spruance DD-963.

You don't want elaboration about it from me, I would steer you wrong! I need it drawn out in crayon for me. New to the stage motors myself, just got a crate of parts a month or so ago, now collecting the rest.

I will shoot you a PM. Curious to see how long you been here, etc. I assume you are on wet side 32nd as well.

 

[Nick Micale]

I was justgetting my car back on the roadd and ready to tune and on simple acceleration my timing chain broke destroying the front cover, bending valves and marring the tops of the pistons. After a slow and meticulous disassembly we could not find any real reason for it to fail. Has anyone else had this happen to them, is there anything inparticular I should look for?? Any help would be appreciated.

I have broken 5 timing chains in the past 4 years and still have no good explanation?

Only destroyed one front cover and always had to replace valves. This is with a 9-10 sec. build with over 100 runs per year. Last 2 chains broke within 50 runs. Other local race Buicks are having the same problem.

Gear drive is out of the question in my case, and belt drives in other local race cars, not Buicks, require frequent replacement.

Currently I replace the chain often until we find a satisfactory solution among what we are testing.

 

[Squid4life]

What about cryo treating them? Think that could prove beneficial? I have heard a lot of good things about cryo treating parts, mainly from a machinist/ farmer back home who does it on the parts they machine (when requested) as well as some farm implement part. Makes them last a whole lot longer. Was looking into taking a load of parts home for it if the time is right next time I go back.

 

[oldtimer]

Dare I ask how much those Danny Bee's are for these motors? I guess "If you have to ask...".

EDIT: Nevermind, saw your new thread.

For those of you who have broken a timing chain, you'll know that the cost of a Danny Bee belt drive set up is a "bargain" compared to the carnage costs caused by a broken chain. Always remember, it's not a matter of "if" your timing chain will break, it's only a matter of "when". Mine broke on start up and a friend's broke driving down the road at 50 mph.

Hopefully, yours won't break at the big end of the track.

George

 

[Nick Micale]

[.........Hopefully, yours won't break at the big end of the track.

George[/B]

A couple of mine broke at the big end, and one in the burnout box, carnage is the same.

Until we have this chain breakage under control, my solution is to replace the chain every 40 runs.

For me, spending about $60 on a new chain, and 1/2 day labor, is simpler than the other options.

The "new" German made chain we are now testing has links visibly larger than existing chains, supposedly better material and heat treated for more strength.

I will be 2-3 months before field and lab testing will be completed.

 

[oldtimer]

Nick, I think we all recognize the harmonics on our v6's is an issue. Running metal to metal retains the harmonics. I have two gear set ups but I want to dampen the harmonics. With the spring pressures that we run and our camshaft configuration, the harmonics will still be there but they can be dampened with the belt drive.
I realize that there are chains out there and gear drives that are doing OK but I think the extra insurance of the belt drive will help. The majority of the much faster cars than ours depend on belt drives. Ther must be a good reason they are.

I'm certainly not an expert but I am a casualty of the chain breakage problem. You just don't know when that chain is going to break, that's the issue in my mind. I'm certainly open for more experienced advice though.

respectfully,

George