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Cam Gear Drive Onto Inlet Cam

Noddy

By Noddy,
in Engines & Forced Induction

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Noddy Proficient

Noddy

Posted
Posted (edited)

The big man up stairs on occasions (in my opinion any way) must sometimes need a laugh and makes dumb stuff go wrong. For example, some 18 months ago the Cambelt tensioner stud in my R33 GTST just snapped in one clean faccet. Result was it ate some valves. A random act of GOD? I rebuilt the motor and the car from the ground up.

Just this week while running in the newly finnished machine, checking and fixing the little things, BEHOLD!!! another random act of GODLENESS. Checking to see if an oil leek from the oil cooler sandwich plate was fixed i started the motor cold, let it idle for 2-3 min to get some temp into it. I gave it 3 quick mild blips on the throttle bodie to about 2-3000 rpm. Comming down from the third blip there was a fast tapping sound. It got louder and the motor just turnd off. It did not jar, just stoped as if the key was turned off. From he start of the noise to engine stoped was abou 3-5 sec. Then I said some,. no, a word very loudly, sounded like truck.

Testing showed,

0 compression in every cylinder.

Cams turn fine (not broken cam).

Pittions all go up and down (not a rod prob)

All timing marks line up fine(not a timing belt slip)

As I took it appart I took photos so I could try to trace the cause. When I got down to head bolts I found that the Inlet cam was 1/4 of a turn out of place. The retainer bolt was still at the correct tension and onct the cam gear was removed, the drive/shear dowle was sheared it 2. This has bent/broken every inlet valve and guide. How does that type of thing happen???

I have been left asking myself if I didnt put it together properly?

Is there only the 1 small dowle pin and the bolt holding and driving the cam?

How does the bolt & spring go together in the nose of the gear? did I get that wrong?

Anyone with answers or suggestions?

(pics to come)

Edited by Noddy
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Godzilla32 Veteran

Godzilla32

Posted
Posted

Not that it will help much now but for future reference you should always replace the tensioner stud and idler bolt when doing a timing belt. Not to mention the tensioner and idler themselves. Apparently vy common to find either a collapsed tensioner/idler or sheared off bolt/stud.

Good luck with fixing it up. Check and double check everything :mellow:

Noddy Proficient

Noddy

Posted
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Posted (edited)

I had the washer under the bolt and needed to hold the cam with a shifter to undo the bolt. Tension checked out before un doing. The tensioner stud I put down to experience ages ago, but this drive pin...

Pics are comming, just havn't been home yet. working too much.

As for these things happening in 3's, Im hopeing this is the third thing.

1, Tensioner stud

2, Machineist/engine builder stuffup. #1 bigend not sized properly and cheep bearings.

3, cam drive pin

lets hope.

Edited by Noddy

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