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Crankshaft Timing Belt Sprockets: The Truth


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73 replies to this topic

#1 WJM

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Posted 27 December 2006 - 08:47 AM

All previous information in the post that was here originally was wrong.

Here is the correct information.

On the left, is the FRONT sprocket. On the right, is the REAR sprocket. Here are the pictures. Notice that the RIGHT one has a groove on the back of it. This one denotes that it goes nearest to the rear of the engine. The LEFT one does not have a groove, so therefore it goes on the front.

http://wjmrallyespor...ts/DSCF5331.JPG
http://wjmrallyespor...ts/DSCF5332.JPG

#2 WJM

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Posted 27 December 2006 - 08:48 AM

1st reserved post....for more information in the future.

#3 WJM

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Posted 27 December 2006 - 08:49 AM

2nd and final reserved post...for more future information.

#4 bgd73

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Posted 27 December 2006 - 09:52 AM

My spfi is backwards, my wagon isn't. My wagon with a carb oem doesn't seem to be off at all, they both line up.:confused: they are both oem.
There are different cams for the carb to spfi, spfi taking the wrong timing dramatically due to the btdc timing on the cam. Carb cams are quite tight to fill the cylinder, an old soob could go years incorrectly without much notice. Turbo engines would really know there was something wrong, more than any other with timing off.
Any carbed ea82 photos oem? I regret not taking one of mine- the teeth weren't even off aligned from each other, they were in same spot, or at least very closely.Another reason for my questions about this.:-\

#5 mikeshoup

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Posted 27 December 2006 - 10:17 AM

Good info on which sprocket is which WJM!

I doubt yours were aligned BGD, unless someone put two of the same sprocket on :-\

The fact they're "misaligned" has nothing to do with the cams. They are misaligned because the cam sprockets are the same, so in order for the belt to fit correctly, and still have the camshafts exactly 180 degrees apart (which they should be... if not, something IS wrong), one sprocket needs to be set slightly off from the other.

Read the FSM sometime, even my 86 mentions this. Plus, one belt has something like 48 teeth between the alignment mark on the cam sprocket and the crank sprocket, and the other has 44.5. The FSM even says this.

The fact that your carb's sprockets are perfectly aligned is not a factory job, it was someone who didn't know what they were doing and probably put two of the same sprockets on.

#6 Hodaka Rider

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Posted 27 December 2006 - 11:38 AM

Good info, Will. To all other posters or would be posters: if you think you know something different (Will and mikeshoup have quoted factory service manuals) please provide actuall proof in the form of factory part numbers or TSB's. We don't want false information ruining this important thread. This should be a candidate for the USRM forums, so maybe false info should be removed?

#7 WJM

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Posted 27 December 2006 - 11:43 AM

I'll be getting FSM info up tonight I hope.

#8 Davalos

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Posted 27 December 2006 - 01:37 PM

Oh,man this rocks! And it couldn't have been better timing, either!

THANK YOU!!!! I'm just now getting to this part!

#9 grossgary

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Posted 27 December 2006 - 03:23 PM

I doubt yours were aligned BGD, unless someone put two of the same sprocket on :-\

mike is right here. if you bought a Subaru with two different tire sizes on it - what is the most likely explanation? that Subaru made one special vehicle different from all the rest, different from the FSM, different from the owners manual and never mentioned it? no, that someone installed the wrong size tire. if you noticed a difference in sprockets on an EA82, it would more than likely be due to someone previously working on it.

#10 WJM

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Posted 27 December 2006 - 03:35 PM

and since EA82's have been around for 20 years...most likely someone has been in there.....

#11 GeneralDisorder

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Posted 27 December 2006 - 05:15 PM

Thank you for the clarification and the pics. Accurate information is most welcome.

I too have noticed that the "pin" in the crank pulley is not always there. My 86 doesn't have one, but with the N/A's it doesn't seem to matter much.

GD

#12 WJM

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Posted 27 December 2006 - 09:47 PM

Ok, so this eveing I took my newest RX and put it under the knife.

The engine that is currently in it was the one in my 87 that once upon a time put down the 165hp/220tq to the wheels at 14psi on just bolt on mods....since then its seen other 30k miles with some track days, autox and alot of hard street driving. Combined mileage is around 60k miles since pleiades and I first put it back together with peices that were around 180k miles old....


What did I find?!??!?!?

The timing belt sprockets WERE on BACKWARDS.


Hmmm....

The engine did exibit some rough idle from time to time, and at stock boost levels DID seem weak.

So after correcting that, the engine ran alot smoother.

From there, I rechecked the distributor timing. It was one tooth off from the cam. Corrected that and set timng at about 22 deg. Now, its perfect.

Now, there is a coolant leak. :mad:

The car is a tad quicker now, and DEFINATLY runs a whole lot better now.

#13 jeffast

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Posted 27 December 2006 - 09:48 PM

cool, thanks for finally showing the truth in this area will

#14 hooziewhatsit

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Posted 28 December 2006 - 01:23 AM

so in theory, for any of us wanting to verify our sprockets are on correctly, we can just remove the clutch fan, and remove the crank pulley off. Then, if we see the dot in the sprocket, we'll know everything is fine. If we don't see the dot, we'll know they're backwards, right?

-Dave

(have a feeling they're backwards on my 88GL, getting some pinging under load, and everything else is fine)

#15 grossgary

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Posted 28 December 2006 - 03:04 AM

If we don't see the dot, we'll know they're backwards, right?

or replaced with an incorrect sprocket. sprockets can get damaged, replacement with the wrong one could leave the dot still up front (but the wrong one in the rear) or could mean only the front one is wrong (rear is fine). i don't know if XT6 sprockets are different from EA82, but i do know they will interchange on the crank...there's another possible screw up.

#16 Phizinza

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Posted 28 December 2006 - 04:26 AM

This is great info WJM. Thanks for sharing. I want to go pull the timming covers off my dad's wagon now... Interesting to hear about your RX and how it was off. Faith restored in the old gen motors again?

Cheers again mate. :headbang:

#17 WJM

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Posted 28 December 2006 - 07:07 AM

I've never really lost my belief in the EA82's. Parts are still WIDELY avalible, and knowledge of those engines are still avalible from the 'old timers' at SOA in the form of books and people.

One day, I'll be one of those old timers that have unlimited resources about the engine. Right now, those guys are getting harder and harder to find....so it makes it very difficult to the average person to do the right stuff with this engine.

hooziewhatsit: You dont have to pull the fan off. Just take the crank pully off. I'd pull the entire thing apart tho to check front AND rear.

#18 subeman90

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Posted 28 December 2006 - 10:40 AM

let me know when this is all completed...i want it for the USRM.

#19 WAWalker

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Posted 28 December 2006 - 03:13 PM

Ok, here is the CORRECT layout of the sprockets on the crankshaft. Note the 'dot' around 5:30 on the front sprocket. This identifies the FRONT sprocket (SUBARU calls this the '#2' sprocket), as the rear one does not have a DOT(#1).



One more note: Apparently the '#2' sprocket, aka the front most one, was supposed to have a dowel pin in it from the factory, as to not allow the crank pully to rotate under the bolt and work loose. That is the original method of ID'ing the front sprocket. However, FUJI was smart enough to know the dowel would sometimes come out....thus, the DOT is there to ONLY ID it as the front/#2 sprocket.


Actually if you read the FSM.............#2 sprocket is the sprocket that drives the timing belt for the bank with #2 cyl (left bank). This is the REAR MOST sprocket. And I quote from the FSM......"Sprocket No. 2 can be identified by the absence of dowel pin."

#20 JWX

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Posted 28 December 2006 - 10:22 PM

Actually if you read the FSM.............#2 sprocket is the sprocket that drives the timing belt for the bank with #2 cyl (left bank). This is the REAR MOST sprocket. And I quote from the FSM......"Sprocket No. 2 can be identified by the absence of dowel pin."



One more note: Apparently the '#2' sprocket, aka the front most one, was supposed to have a dowel pin in it from the factory, as to not allow the crank pully to rotate under the bolt and work loose. That is the original method of ID'ing the front sprocket. However, FUJI was smart enough to know the dowel would sometimes come out...

:rolleyes:

#21 WJM

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Posted 28 December 2006 - 10:31 PM

Actually if you read the FSM.............#2 sprocket is the sprocket that drives the timing belt for the bank with #2 cyl (left bank). This is the REAR MOST sprocket. And I quote from the FSM......"Sprocket No. 2 can be identified by the absence of dowel pin."


Actaully....if you read BOTH the 86 FSM...and the 91 FSM...both are different in their wording!!!!!!

The 86 speaks what you just spoke, and I just read that in my 86 FSM set.

However, the 91 FSM that the dealership ownes, speaks exactly the opposite of what the 86 FSM states.

However, both state that one or the other can be identified by the presence OR absense of the dowel pin.


*WJM is now looking for the training books for the EA82*

#22 WJM

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Posted 28 December 2006 - 10:43 PM

In both training books that I have....neither of them mention ways to ID the two from each other.

Both of the books refer to them as the 'inner' and 'outer' sprockets.

Apparently they must think that you will be smart enough to know that they are inner vs outer for a reason, and NOT to interchage them.

#23 GeneralDisorder

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Posted 28 December 2006 - 10:55 PM

One wonders why subaru didn't just cast the suckers as one peice. Maybe has something to do with assembly line process or something. Certainly doesn't seem it would be a detriment for the mechanic.

GD

#24 WAWalker

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Posted 29 December 2006 - 10:08 AM

:rolleyes:


Me thinks you should read it again before rolling your eyes.

#25 WAWalker

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Posted 29 December 2006 - 10:43 AM

Actaully....if you read BOTH the 86 FSM...and the 91 FSM...both are different in their wording!!!!!!


I was kind of wondering after my post if this would be the case. Dosen't surprise me at all.

The 86 speaks what you just spoke, and I just read that in my 86 FSM set.


The 86 FSM is the one that I quoted.

However, the 91 FSM that the dealership ownes, speaks exactly the opposite of what the 86 FSM states.


Again, not surprised.

However, both state that one or the other can be identified by the presence OR absense of the dowel pin.


*WJM is now looking for the training books for the EA82*


So in order to know the REAL truth..........you would need to read each FSM from '85-'94 and break this info down buy year and probably Carb. vs Injected.

Also, I'm not sure that all EA82 front sprockets had dowel pins in them from the factory. The ones that I have seen, the dowel pin was actually a small roll pin. So the hole for this pin is smaller than the other holes that you see on the sprocket. So it would be easy to determine even if the pin is missing. And if they all have this all EA82 crank pully will have a small hole in the mating surface to the sproket.
I make it a point not to keep a lot of spare EA82 parts lying around so I can't look or post any pics, but as memory serves, not all EA82 crank pullys have this hole.
If they do please correct me.




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