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Old 05-14-2014, 09:46 AM
Rovch Rovch is offline
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Unhappy Now what? (CAM broke off)

Just wanted to share my find last night.

Two weeks ago I've replaced an old KA24DE in my S14 with an OEM Rebuilt one. 500 miles into a break-in, it refused to start so I did a compression test (after making sure that I had A/F/S). The results were painful to see 0 0 0 60.

I'll let the pictures tell the rest of the story:






And as if the car thought that breaking the CAM was not enough to ruin my night (what's missing is somewhere in my engine):



Just sold my SR swap right in time as well
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Old 05-14-2014, 09:56 AM
Def Def is online now
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There's your problem!


That sucks.. I always thought the KA timing chain setup looked like it was putting a lot of stress on the cam.
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Old 05-14-2014, 10:00 AM
Matt93SE Matt93SE is offline
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Too much timing chain tension maybe?

Wonder if it bent any/all of the valves? (have to put a new cam in and check it..)

Who did the rebuild?

I think I still have a set of OE S14 cams in the garage if you need them, but they might be a touch rusty from the Houston humidity.
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Old 05-14-2014, 01:13 PM
Rovch Rovch is offline
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Quote:
Originally Posted by Matt93SE View Post


Too much timing chain tension maybe?

Wonder if it bent any/all of the valves? (have to put a new cam in and check it..)

Who did the rebuild?

I think I still have a set of OE S14 cams in the garage if you need them, but they might be a touch rusty from the Houston humidity.
As in upper chain tensioner is too tight?

About to go pick up another CAM from a friend. But thank you for the offer.

A friend of mine rebuilt this motor. I know it's got new rings, gaskets, and bearings. Do not know what else was done during the rebuild.

What I am going to do is pull the oil pan and front timing cover to clean everything out. Then install another CAM and hope for the best. Unfortunately I don't believe that a camshaft would just break. It's got to be either warped camshaft, warped head, or some kind of oil/heat issue. Or maybe something else I didn't think of.
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Old 05-14-2014, 01:26 PM
Def Def is online now
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Was the bolt under torqued? On SR's it's like 100 ft-lb I think.
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Old 05-14-2014, 01:55 PM
Matt93SE Matt93SE is offline
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Given the location of the break, it makes me wonder a couple things.. 1. was the cam bolt OVER torqued, causing cracking in the end of the cam.
2. the cap at the end of the head could be off/wrong/backwards, which caused some strange loading and possibly binding on the cam. however, the wear on the inside of the cap doesn't look abnormal so I tend to think this isn't the issue...

just random thoughts from a guy that's built 3 engines in the last 20 years. it's worth what you paid for it.
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Old 05-14-2014, 06:31 PM
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Looks under torqued due to the failure happening around the root of the keyway. If I was looking at it in person I could maybe tell which part failed first due to the presence of fatigue beech-marks. The back end of it failed due to torsion tho, so definitely while it was spinning.
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Old 05-15-2014, 10:02 AM
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I know on the SRs it is pretty common to break the camshafts by over torquing the caps. They are surprisingly low torque specs 6.7 to 8.7 ft-lbs. Also the order you torque them is important.
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Old 05-18-2014, 04:20 PM
G-E G-E is offline
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To me it looks like it failed at the dowel, and then radiated back towards the oil hole... if that's the case, it's likely because the chain was going one way, and the cam tried to go the other way

Pull the head, tell us what you find, carnage is always awesome to look at :P
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Old 05-18-2014, 07:14 PM
Rovch Rovch is offline
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Slapped another intake CAM on and got very sad compression results: 0 80 80 15

Also discovered that my upper bolt on upper chain tensioner was broken off inside the head. Thankfully, I extracted the remains without too much trouble.

Talked to the engine builder - he will be taking partial responsibility for it. He's going to pull the engine out and do the work as long as I can figure out head situation. Tomorrow I am going to pull the head of my spare KA (unknown head condition) and hopefully have enough valves to make one good head out of the two.

Will update with pictures once I tear into the motor.
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