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This Has Never Happened Before!

stuartlaw_78
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stuartlaw_78 Community Regular

stuartlaw_78

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Posted

Hi all..

Just rebuild my engine and have been running it for a week and today it died!!

It seems that the crank angle sensor completely seized up and snapped the end of the exhuast cam off!!

Has anybody ever had this happen??

Also, the 4 bolts that hold the exhuast cam gear on were scrapping against the crank angle sensor and there are metle shavings everywhere!!

Anybody shed some light on this????

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stuartlaw_78 Community Regular

stuartlaw_78

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I actually installed it and did it to the book...

Why is it touching the bolts???

I left the timing belt cover off, I think the sensor bolts onto this after the cover is put on so in theory, if I don't put the cover on, then, the sensor would bolt up that much closer to the cam gear, therefore, touching the bolts??

Does that sound possible???

SteveL Mentor

SteveL

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Posted
It seems that the crank angle sensor completely seized up and snapped the end of the exhuast cam off!!

This is very unlikely.....almost certainly the camshaft was cracked, possibly at installation. Under load with the engine running the crack progressed until the camshaft failed completely. The metal shavings, etc are probably from when the cam pulley bolts contacted the back of the CAS or the CAS mount at failure - the engine would have continued to turn for a short time after the ex cam failed.

I've seen a few failures of cams in RB engines as a result of incorrect installation - when doing up the cam cap bolts it's quite easy to put a bending load on the camshaft, and cast iron doesn't take kindly to that.

Anyway, that's my theory, I could tell for certain by examining the camshaft.

One other thing - you need to hope that valves didn't contact pistons.

stuartlaw_78 Community Regular

stuartlaw_78

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Thanks for all your comments mate, I will take them on board....

The actualy cam is in one piece, it's just the very tip of it that the crank angle sensor slips onto that snapped off.. that piece is still in the shaft of the sensor when I took it off....

Does that clarify things anymore...

SteveL Mentor

SteveL

Posted
Posted
The actualy cam is in one piece, it's just the very tip of it that the crank angle sensor slips onto that snapped off.. that piece is still in the shaft of the sensor when I took it off.... 

Take some pictures if you can, I'm intrigued by how much of the cam has broken off.

stuartlaw_78 Community Regular

stuartlaw_78

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Yeah, I will try and take some pics of it.... keep an eye on this thread.. I'll post them here tomorrow..

I will be sure to put spacers in when I put it back together.. an expensive lesson!!

If I were to put aftermarket cams in, what would you all recommend and can I run cams with more lift and longer duration with the standard ecu??

I'm guessing that I can but I just won't get the power gains until I get the ecu changed....

stuartlaw_78 Community Regular

stuartlaw_78

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Posted

Thanks all..

damn, I did so well with the rebuild too... Did it all and I stuff up something like this... feel like a damn idoit!! Ahh well, you live and learn I guess.....

If anybody has an exhuast cam for the rb25det, let me know..

I have been told that the rb20det is exactly the sam cam so I can use that if I have to......

blind_elk Grand Master

blind_elk

Posted
Posted

The half-moon is only an aid to getting the angular relationship between the cam and CAS correct. The CAS keeps turning because of intermeshing of the teeth set on the CAS and the cam.

Without the half-moon, you need to visualise where they would line up. If you get it wrong, the engine won't run (but no damage is caused).

stuartlaw_78 Community Regular

stuartlaw_78

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I would love to be able ti use the cam still but it didn't just snap off the half moon part of it, it snapped the whole spline off of the cam down to the end!!!

The whole piece was jammed into the CAS!! Nothing left for the CAS to grab onto caus it got snapped off down to the base!!

I just brought another cam and fitted it last night... Runs like a dream and yes, I've now put some washers in place of the timing belt cover so the CAS doesn't touch the cam geard bolts....

A valuable lesson learnt but if this is the only mistake I've made with the rebuild, then I'm as happy as a pig in....... ;-)

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