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1G Helical gears and OEM stubby shaft

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I collect good oem cases when I get engine cores. I will run a cleaned up and inspected 25 year old oem case before anything aftermarket.

I think that the case I pulled off the engine is an OEM one. Never had a bearing failure or anything. I could reuse it but figured replacing it would be better.... Maybe that's not the case (no pun intended).
 
It looks like it's already been covered here, but i want to confirm my experience w/ helical gears was that it ate the case up. This could be the result of other factors rather than just part fatigue or failure. I would imagine the helical gear has thrust load that is a lot more than the straight cut gears and i think that's why people want straight cut.... they're not as prone to eating the case out. My disclaimer is that I have no "facts" about this and only my experience to go on. I realize that may not satisfy some people.

I'm just a worker bee at a tech company though. buzzbuzz

Maybe its just me, but judging by the marks on the case it kind of does seem like the timing belt tension was too tight at some point. Maybe even an oiling issue to the stub shaft. It looks similar to those stub shafts that used to be around with out the oiling grove. How often were you checking the tension? How many miles were on the motor? Which stub shaft was used?

The marks on the pump case are on the opposite side of where it'd cause gear contact if the belt was too tight. I may be wrong but that's what it looks like to me.

Donniekak - answered it.... the marks look like the drive and driven gears pressing apart and cocking sideways. The support from having a full balance shaft would prevent this failure.
 
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No actual data, but my theory is the helical gears not only have thrust loads, but also an axial rotation due to the profile of the teeth and where they engage throughout their rotation.

Both of these effects could be mitigated some by the stock balance shaft, whereas the stubby shaft doesn't have the added weight or support to help either issue.

I had a stock BS turned down to a straight shaft and used that in my current setup (AMS style), and I don't think ill use anything else for my motors. Maybe if I hit baller status, I'll go for the FFWD oil pump at some point.

Do you have a picture of the turned down shaft?

The marks on the pump case are on the opposite side of where it'd cause gear contact if the belt was too tight. I may be wrong but that's what it looks like to me.

Donniekak - answered it.... the marks look like the drive and driven gears pressing apart and cocking sideways. The support from having a full balance shaft would prevent this failure.

Maybe if I can find someone to turn the shaft down for me at a reasonable price I will go that route... I just need to see which parts need turned down so I can ask my machinist about it.
 
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Exact shaft from my build.

Nice. I'm wondering if anyone has reported the same failure as everyone else while using a turned down shaft. Assuming the answer is no, this will be the main reasoning behind me going with a GSC or turned shaft.

I assume with this shaft, there is no need to align the oil pump gear when timing or align the new shaft with the marks on the oil pump gears?

What did you do to install the bearing? Just hammer it in with the old front balance shaft?
 
The marks on the pump case are on the opposite side of where it'd cause gear contact if the belt was too tight. I may be wrong but that's what it looks like to me.

Donniekak - answered it.... the marks look like the drive and driven gears pressing apart and cocking sideways. The support from having a full balance shaft would prevent this failure.

The marks on the cover are exactly where I'd expect to see them if the belt was too tight.

For those that are interested, try this mental exercise. Refer to the below picture while doing this. The arrow in the below picture represents the force applied by the belt on the sprocket and, inherently, the shaft.

***Updated with clothes pin, to illustrate.
  • Find a pen and grab the center of it with your index finger and thumb on your right hand (clothes pin); for representative purposes, this is the bore for the shaft or the bearing area of the housing.
  • Orient the pen as if it is the shaft in this picture, like the pen is coming out of the screen and at the location of that bore.
  • With your left hand, push the end of the pen that is closer to the screen in the direction of the arrow.
  • Now answer yourself this: what does the end of the pen closer to you do?
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In these, the clothes pin is representative of the bore of the oil pump housing for the drive shaft.

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This is why the damage to the case is where it is and the damage to the gear cover is 180 degrees opposite. Like I said in the thread I linked to earlier, if the belt is too tight, it won't matter what gears you have when using the stubby shaft -- you'll see the same damage. The turned down shaft or original shaft that would utilize that extra journal bearing would help in that scenario.

There are no thrust loads created by the straight cut gears so as long as the oil is clean and clearances are within spec and assuming the belt is not overtightened, this should be an extremely reliable system, regardless of shaft type. As for helical gears, they inherently create thrust loads. The casing is the only component that will provide the reactive force (or support) for that load. So, again, as long as the oil is clean and the clearances are within spec, I would expect the system to work very well for a very long time. However, it does have the risk at some point eating into the case.
 
The marks on the cover are exactly where I'd expect to see them if the belt was too tight.

For those that are interested, try this mental exercise. Refer to the below picture while doing this. The arrow in the below picture represents the force applied by the belt on the sprocket and, inherently, the shaft.
  • Find a pen and grab the center of it with your index finger and thumb on your right hand; for representative purposes, this is the bore for the shaft or the bearing area of the housing.
  • Orient the pen as if it is the shaft in this picture, like the pen is coming out of the screen and at the location of that bore.
  • With your left hand, push the end of the pen that is closer to the screen in the direction of the arrow.
  • Now answer yourself this: what does the end of the pen closer to you do?
You must be logged in to view this image or video.

This is why the damage to the case is where it is and the damage to the gear cover is 180 degrees opposite. Like I said in the thread I linked to earlier, if the belt is too tight, it won't matter what gears you have when using the stubby shaft -- you'll see the same damage. The turned down shaft or original shaft that would utilize that extra journal bearing would help in that scenario.

There are no thrust loads created by the straight cut gears so as long as the oil is clean and clearances are within spec and assuming the belt is not overtightened, this should be an extremely reliable system, regardless of shaft type. As for helical gears, they inherently create thrust loads. The casing is the only component that will provide the reactive force (or support) for that load. So, again, as long as the oil is clean and the clearances are within spec, I would expect the system to work very well for a very long time. However, it does have the risk at some point eating into the case.

Makes a ton of sense. Thanks for breaking it down. So in your opinion, which option has the least potential for destroying an engine or front case: The GSC shaft with helical gears, or a stubby with straight gears?

That would take into account the potential for a balance shaft bearing to fail.

Also I would assume that running straight gears in an ACL pump would be a bad idea?
 
I tried following your exercise, and I think I did it correctly but I guess it still doesnt make sense to me because the belt being tightened would pull the gear towards the center of the motor and make contact on the side of the surface of the case that is closer to the center of the motor. The wear on the side away from the center of the motor looks like gear spreading. I'm definitely not tryiI'ng to be obtuse here but in my mind it looks like it'd create the damage on the other side if it were the belt.

In the scenario you laid out, when you push the side of the pen that is closest to the screen in the direction of the arrow, it would create the damage in the photo, but the belt isn't holding onto the shaft end of the oil pump assembly, it's holding the front side of it on the gear..... that's I guess where this doesn't make sense to me. It looks like it'd be on the other side with the forces of a belt being too tight acting on it.

Straight gears in an ACL pump should be "fine" as long as the machining of the pump from the manufacturer is "fine" (in spec). Anything using the stubby shaft is prone to damage from overtightening the belt and deflection caused in normal use..... many factors are at play here. The helical gears are prone to damage from thrust loading the gear.

The oil pump is really one of the weakest parts of a 4g63 IMO.
 
Makes a ton of sense. Thanks for breaking it down. So in your opinion, which option has the least potential for destroying an engine or front case: The GSC shaft with helical gears, or a stubby with straight gears?
Taking all potentials into account, my opinion would be the GSC shaft with straight cut gears. Having said that, I run straight cut with a stubby shaft.

Also I would assume that running straight gears in an ACL pump would be a bad idea?
No idea. I've not been through enough pumps to know what outside of OEM would be okay.

...the belt being tightened would pull the gear towards the center of the motor...
It would.
and make contact on the side of the surface of the case that is closer to the center of the motor.
Not on in the inside of the case. On the sprocket side, yes. Another way of putting it, the housing would basically act like a fulcrum for the shaft: since the force of the belt is pulling the sprocket towards the center of the engine, the shaft itself inside of the casing (gear side of the casing) will move opposite the direction the belt is pulling, so down and to the left where all the wear is showing for the case itself.

The wear on the side away from the center of the motor looks like gear spreading. I'm definitely not tryiI'ng to be obtuse here but in my mind it looks like it'd create the damage on the other side if it were the belt.
I think you're seeing part of it. The gear on the end of the shaft inside of the pump is wearing the gear cover the way you are describing. If you can get the pen visualization down, take the same motion of the pen and translate it to a coin or a disc which would act like the gear. Then imagine that the gear is enclosed on both sides. With that motion, it becomes very obvious how the wear patterns for those two pieces were achieved.

In the scenario you laid out, when you push the side of the pen that is closest to the screen in the direction of the arrow, it would create the damage in the photo, but the belt isn't holding onto the shaft end of the oil pump assembly, it's holding the front side of it on the gear..... that's I guess where this doesn't make sense to me. It looks like it'd be on the other side with the forces of a belt being too tight acting on it.
Yes, but remember what your fingers are representing. The picture is for reference, your fingers holding the pen become the casing. So when you push the end of the pen closest to the screen in the direction of the arrow, you are pushing on the belt side of the casing. The end closest to you would be what you are seeing the shaft do inside the casing.

Sorry this is probably becoming more convoluted than it needed to be. :coy:

Edit: the other thing we all need to remember here is that the internal shaft attaches to the top gear of the oil pump. That gear is technically double captured by the casing and gear cover on either side of it. Statically, that makes the rear journal bearing in the block absolutely useless. Dynamically, I could imagine it being helpful.
 
Taking all potentials into account, my opinion would be the GSC shaft with straight cut gears. Having said that, I run straight cut with a stubby shaft.

Are you using a 1990 front case to go with the straight cut gears?

Ideally I would run the straight gears with the stub shaft. But since I am going to be using the ACL cover, I will probably just stick with the helical gears that it came with to avoid any clearance issues.

So as long as I am using the GSC shaft, even with helical gears, then this *should* work and would just pretty much mimic the OEM set up right?

Since I have decided to go with the GSC shaft for the extra reassurance, what methods do people use to re-install a new bearing for the rear shaft without destroying it?
 
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You can always use a cam bearing installation tool, but it’s pretty much the same thing.

Ill just use the shaft and try to tap on it as lightly as possible to get it in. As long as it spins freely I'm sure it will be fine as there is no real load on it like the crank.

Thanks Donnie. You have been a huge help. As well as every one else that chimed in with their experience. Thanks again everyone.
 
I used a bearing installation tool for reference, put the bearing in the freezer for a bit before hand to shrink it, taps right in then expands to fit.

I forgot about the ol' freezer trick! Thanks! After freezing it I assume it taps in easy enough that I could use the front balance shaft without damaging it?

I ordered the GSC shaft today....along with the rods, pistons, and every other part I could think I needed for the build. My debit card about caught fire LOL.
 
Certainly should, I just have to justify my besring installation set, haha.

Do you have a link to the one you have? Just in case I get ambitious and buy one haha

Also there is no need to line anything up with the GSC shaft correct? Like the marks on the oil pump gears and timing mark.
 
Do you have a link to the one you have? Just in case I get ambitious and buy one haha

Also there is no need to line anything up with the GSC shaft correct? Like the marks on the oil pump gears and timing mark.

Mine is one i got at sears years ago, only used it 3-4 times, I believe it's craftsman but ill have to go dig it out to be sure.

And no, no need to line anything up with the race shaft.
 
Mine is one i got at sears years ago, only used it 3-4 times, I believe it's craftsman but ill have to go dig it out to be sure.

And no, no need to line anything up with the race shaft.

No need to dig it up. I will probably end up using the front shaft anyways. Thanks for the information though! It helps a ton!
 
Thank you for the thorough explanation.

Another thing to note that may seem obvious.....

* If you're using a stub shaft then you install the balance shaft bearing 180* out so it doesn't create a low oil pressure problem for your entire system.
* If you're using a oem balance shaft or any other turned down shaft that has the journal on the other end, you MUST make sure that proper oiling is present there.

I'd just hate to hear someone ruined their motor over something silly like that.
 
Thank you for the thorough explanation.

Another thing to note that may seem obvious.....

* If you're using a stub shaft then you install the balance shaft bearing 180* out so it doesn't create a low oil pressure problem for your entire system.
* If you're using a oem balance shaft or any other turned down shaft that has the journal on the other end, you MUST make sure that proper oiling is present there.

I'd just hate to hear someone ruined their motor over something silly like that.

This is the rear shaft. There is no hole in the bearing itself. It is oiled via the shaft. For the front shaft bearings your are exactly right. Since I will be deleting the front shaft this still holds true for that part.
 
I have bought two OEM oil pumps for my cars in almost 20 years and never had to worry about them...ever. The one in the VR4 has been through multiple engine problems (unrelated) with no issues. Straight gears and stubby shaft with properly tensioned EVO IX timing belt. Run good oil and install it correctly. Both cars were revved to 9,000rpm.
 
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