Puzzling question--Anyone know why this might happen?

[honda_vtec2]

A short while ago i was driving/cruising doing 80kph. I felt a slip in the power band and started hearing lifter clatter. I pulled over to the side of the road and checked my timing belt. It was slack, still in good condition. After getting the car towed home. I then inspected the tensioner, and the internal springs were damaged. Upon removal the tab was still in it's slot, but the larger tab on the end was bent to hell. I'm not too sure what happened here........After i timed the engine up. The crank and ip were still timed but the cam was out, which caused camshaft and lifter/bore/valve damage. This tapered end was hand sanded and cleaned with brake clean and torqued to 42/ft lbs the last time i did the job.

All timing components were changed 40k ago. Everything was torqued to spec

Question:

Anyone have any ideas what might have happened.

Note:

I've done this job 3 times with new parts since i've owned the car. Roughly putting 80k on it since. The 3rd time around, i rebuilt the crank and hopefully secured it in place, since then it hasn't shifted or loosend. OEM parts have only been used on this car regarding the tbelt components. Cam was original and lifters were INA which had 40k on them as well.

The car is fixed and being driven now, but i still have no clue what might have happened.

 

[G60ING]

one guess: The tensioner failed and then the cam and sprocket shifted when the impact occurred. I think it sounds plausible.

 

[Ski in NC]

Any unexplained event prior to failure where engine misfired when cold engine was rev'd high? Like missing a gear or just a high rev in first gear cold engine?

 

[honda_vtec2]

The day the breakdown occured it was raining, so i was driving it slower than i normally drive. The only thing i can think of was that this past winter i got stuck in back to back stop and go traffic while going to rehearsal. Both times occured in the winter, where it took me 4-6 hrs to get home. Which would normally only be a 2 hr drive at max. I know this prob wouldn't make sense. Other than than i've been driving the car this past year for fuel economy, so i haven't been pushing it past 3500 rpms in any gear. I also have been checking the timing belt components and the tensioner tabs at routine oil change intervals, every 12000km.

The tensioner was a brand new orange faced Litens. I have replaced it with the same. As i have read, they are the choice replacements.

 

[honda_vtec2]

one guess: The tensioner failed and then the cam and sprocket shifted when the impact occurred. I think it sounds plausible.

That was my guess as well. I'm thinking since the internal springs let go on the tensioner. It caused the slack in the belt, which cause the cam to shift out of time. This led to the valves hitting the lifters and the cam somehow shattered 2 lifters and got stuck. Enough pressure to force the cam sprocket to shift. I've checked my logs. That cam bolt was torqued to 42 ft/lbs.

 

[honda_vtec2]

Hey guys, forgot to ask this question, so i figured i'd ask it in this thread.

While i was changing my exhaust manifold gaskets. I forgot to put the spacer washers back on the car (8 of them). I used new copper nuts. Would this create a problem down the road, or a possible exhaust leak?. After all that work, to forget about the washers was a bit dumb on my part ;(. I really don't want to have to do some of the work again to put these in......

TIA

 

[jackgreen]

i would think the danger might be a cracked exhaust manifold.
the aluminum head and cast iron exhaust manifold expand at different rates.

 

[16vjohn]

i would think the danger might be a cracked exhaust manifold.
the aluminum head and cast iron exhaust manifold expand at different rates.

I agree with this. Fix it soon.

 

[honda_vtec2]

I replaced them, and torqued down the ex man again. I still don't understand how these washers play a role with the installation. Just so we are talking about the same parts. It's the washer where the nut goes on to secure the ex manifold.

I did drive the car a good 300km without these washers. I hope i didn't damaged anything on the car.

 

[jackgreen]

I replaced them, and torqued down the ex man again. I still don't understand how these washers play a role with the installation. Just so we are talking about the same parts. It's the washer where the nut goes on to secure the ex manifold.

I did drive the car a good 300km without these washers. I hope i didn't damaged anything on the car.

300 kilometers? car should be just fine.
i think the washers help deal with the stress of repetitive heating and cooling of the manifold and head. the cast iron manifold and aluminum head expand at different rates.