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Old 10-30-2002, 11:24 PM   #1
rallynutdon
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Default Is WRX motor an interference motor

From everything I've heard, it is. I have a chance to buy a motor from a wreck but am being told one of the cam gears was broken in the accident (the car was rolled and every body panel damaged and the radiator pushed back). I haven't seen it yet so I'm not sure if it was totally broken or not and if the belt is still on the gears. Thanks.
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Old 10-30-2002, 11:40 PM   #2
Jon [in CT]
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The WRX's (like any Subaru DOHC) engine, is an interfernece engine. It's possible to damage the valves if the timing belt breaks or jumps a tooth due to an accident.

Last edited by Jon [in CT]; 10-30-2002 at 11:54 PM.
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Old 10-31-2002, 07:39 AM   #3
JenisonWRX
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I've heard its not but if both exhaust and intake valves are open they will hit each other ... but not the piston...

hmmm

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Old 10-31-2002, 11:37 AM   #4
Jon [in CT]
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There's no doubt that the intake and exhaust valves can interfere with each other. From the service manual:
Quote:
Intake and exhaust camshafts for this DOHC engine can be independently rotated with the timing belts [sic] removed. As can be seen from the figure, if the intake and exhaust valves are lifted simultaneously, their heads will interfere with each other, resulting in bent valves.


However, there is some doubt about whether the valves can interfere with the pistons. On the one hand, the service manual says:
Quote:
The piston head has recesses to prevent interference with the intake and exhaust valves.
On the other hand, in another part of the service manual, there is this:
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Old 10-31-2002, 02:30 PM   #5
rallynutdon
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That's my dilemma. A bent valve (or 2) "should" be easier, less expensive to repair than a piston (particluarly if the engine stopped running upon impact?). But I get varying opinions on the piston interference question. I think I'm goin gto wait for the next car with no external engine damage. Thanks.
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Old 11-01-2002, 08:57 AM   #6
rallynutdon
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Default Is WRX motor an interference motor-Do you know for sure?

Doesn't anyone have first hand experience with this? I'm now being told by 1 Subaru mechanic that it's only an issue with bent valves, not a big deal (which is kind of obvious with dual overhead cams). Thanks.
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Old 11-01-2002, 09:09 AM   #7
XT6Wagon
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A motor that is designed to be non-interferance, can STILL have valve to piston contact in the real world. This is why any manual will warn you about not screwing up the timing belt alignment.

Carbon buildup and valve float are the most common causes for this to happen.
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Old 11-01-2002, 11:24 AM   #8
BluSuby
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FWIW I has an accident with the front end of my WRX a year ago. I hit the drivers side front corner pretty hard. I had the dealership fix everything etc... I'm down at the dealership 4 months later to talk to a SOA rep about a warranty issue. He hears my car and tells me he doesn't like the idle of my car. I bring it in a week later to get it checked and it turns out I was out of time by 4 teeth( according to the service manager)!

I'm new to Subarus. I knew they had a slight lope at idle. This was a lttle too much I guess, and I had gotten used to it.

I don't know if it jumped when I wrecked the car or if it was a faulty cam belt tensioner. When they fixed it they installed a new one along with the belt.

Regardless , my car runs fine and I haven't had any problems since.
At the time I didn't think they were interference motors. I'm confident they are now from looking at the Diagram above. I must have been lucky,

Bryan
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Old 11-01-2002, 11:30 AM   #9
bbaerotek
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Post Just valves

I had a wreck in which this happened to my motor. One cam gear just disintegrated. Total bill for the dealer to fix the motor was $2400. Just valves, gaskets, and labor. The funny thing is the $350 gasket set that you have to buy, and then the ANOTHER $150 in misc. gaskets that aren't included in the $350 gasket set.

Anybody know why Subaru makes 3 of the gears out of plastic?
Who makes after market cam gears for the WRX? Or could we just order 3 more of the metal ones and install those? Anyone know if this would hurt the motor?

Brian



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Old 11-01-2002, 12:32 PM   #10
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Recently one of my Friends was complaining that he was only making 5 psi of boost and had no power. After spending a week tyring to find boost leaks and swapping turbos We figured out the problem. He started the car and I noticed the thing would fire over and run the instant he touched the key. Normally on an EJ20 it cranks over one or two revolutions before starting. We decided to check the cam timing and sure enough it was off a few teeth. He took the tensioner off and reset the timming and now he makes full boost again and his power is back.. why it skipped I will never know... I have heard people say that light flywheels can cause this on Subaru motors. He has an MRT flywheel and 5 puck clutch...

CT
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Old 11-01-2002, 12:46 PM   #11
n2xlr8n
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Default Interference

Quote:
Originally posted by Jon [in CT]
There's no doubt that the intake and exhaust valves can interfere with each other. From the service manual:

However, there is some doubt about whether the valves can interfere with the pistons. On the one hand, the service manual says:On the other hand, in another part of the service manual, there is this:
I take this information as yes. Yes it is a int. engine, and yes, the valves can hit the pistons, regardless of the valve reliefs if you A) float the valves or B)Get out of cam timing.
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Old 11-01-2002, 01:54 PM   #12
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I have 12 bent valves and no damaged pistons.
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Old 11-01-2002, 04:20 PM   #13
dug-e-fresh
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My car was hit early in its life and finally after it was finished I got it back and noticed a lumpier idol... took it back to the dealer and they said it was normal... I thought, well its been 4 months since I drove her... so maybe...

Anyway, then I took her to a more local dealer for a CEL (one of those early EVAP codes )

The techs asked me if I had any engine work down, because it wasn't idling right. I said no... just got hit and the timing belt cover had been damaged. (the engine was still running after the accident too... I had to turn her off... $12,500 in damages to the front end!!)

At any rate... I finally got the other dealership to check it out and sure enough, the belt was off "a couple teeth" as they put it.

I had ran at the track with the timing off... hit a [email protected] with just an EBC set to 14.5.

With timing fixed I came back and busted out a string of 13.8s and 13.7s... @ ~97-98MPH.

Thats was over a year ago... now I am running 12s .

def
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