2g oil pump staight cut or helical gears

[DSM_GSX01]

Yes i am in a decision to use strait cut or the helical gears. Witch is a better gear? I know some say straight and others say helical. And with a straight i will get noise right? Or no? and i also this pump is going in a 2.3 stroker with a BSE. I don't know what kind of cams I'm using yet but i know I'm going with a 272 or maybe bigger so if you recommend any cams? Thanks.

 

[myfirstgsx]

It doesn't matter. Please make sure to use a racing long shaft balance shaft eliminator kit and not the stubby one. the long one will keep you from loosing your oil pump at high horse power and high torque.

To answer your question. Its just a matter of what you or the builder prefers. Lots of people like to do little tricks to their motor so that it is different and unique to them.

 

[gofer]

It does matter which oil pump gears you use, actually. If you're using a stubby shaft with helical gears you will thrust load them and they will fail. Always recommend running the '90 straight cut gears if you plan on using a stubby shaft.

Tim Zimmer helped me with my 2.3 build and he provided me with that piece of useful info.

 

[iceman510]

So you run the straight gears in a 7 bolt front case?

 

[95blackGsTurbo]

I ran a new O.E.M oil pump on my 2.3L but I also had the AMS long shaft BSEK. This I felt was the belt option. Never had any oil pressure problems and after a teardown at 22k to replace a leaking gasket there was literally no wear on the gears. Had the same clearances as when I installed them

 

[DSM_GSX01]

So is it better just to use the OEM factory oil pump. They told me if i run straight cut gears it will be a upgrade from a stock pump. I dont know what to pick OEM or the straight cut gears? I can tell you everything thats going in the engine.

 

[DROPthatCLUTCH]

It does matter which oil pump gears you use, actually. If you're using a stubby shaft with helical gears you will thrust load them and they will fail. Always recommend running the '90 straight cut gears if you plan on using a stubby shaft.

Tim Zimmer helped me with my 2.3 build and he provided me with that piece of useful info.

Fuuuuu... Did not know that...

 

[bigbird94]

The gears are sold separate from the case itself. It sounds like you want the 7bolt case w/ 6 bolt straight cut gears. Someone else correct me if I am wrong.

Sorry to threadjack but..
I have two questions that are related to this I'd like to have cleared up.

When I replaced my oil pump I got a new "6 bolt" case but reused my gears from a late 92' (everything was wiithin spec) thinking that 90'-92.5' would all be the same gears...
Should I get the 90' gears if running a stubby shaft?
Are the 90' and 91-94 gears interchangeable in the 6 bolt pump case?


Thanks

 

[DSM_GSX01]

Will i get a loud noise? And also will the gears flow more? Also will they wear out faster?

 

[DROPthatCLUTCH]

It does matter which oil pump gears you use, actually. If you're using a stubby shaft with helical gears you will thrust load them and they will fail. Always recommend running the '90 straight cut gears if you plan on using a stubby shaft.

Tim Zimmer helped me with my 2.3 build and he provided me with that piece of useful info.

Very interested in hearing more about this thrust load problem.

 

[gofer]

Running the stubby shaft you'll want the '90 straight cut oil pump gears, be certain to get them deburred and detailed in your front cover by the machine shop too. Now, if you're running stock BS's or the milled down rear BS then the helical oil pump gears are just fine, you'll still want them deburred and detailed of course.

Using the straight cut gears can result in PK because of the added harmonics so ensuring you've got a properly working and properly torqued (17 ft/lbs) knock sensor is important. I think we can all agree that a little additional noise is better than losing a motor to oil pump failure. Besides that, you've eliminated the BS's in the motor so any additional noise created by the straight cut gears will be masked by the sound of the chassis vibrating through the solid mounts.

Here's a link to them if anyone's having a hard time finding the straight cut gears.

OEM Oil Pump Drive Gear - MD121120
OEM Oil Pump Driven Gear - MD125361​

 

[Hal]

Are the 90' and 91-94 gears interchangeable in the 6 bolt pump case?

According to ASA (CAPS) they are not.

The pump cover part number changed and only later covers are to be used with the helical gears and only the straight gears are to be used in the older covers.

We all know that people are using mis-matched combinations, but there are reported failures when used like this.

Given the potential consequences of a pump failure, it's not (to me) worth the risk. I always suggest putting the proper gears in the proper covers.

The use of a turned down balance shaft makes no difference (regardless of power level).

The stub shaft is located by the back of the oil pump and it's not going off center unless the pump housing rear cover loses it's integrity.

Buyer beware

Hal

 

[DSM_GSX01]

So is stock gears better then straight cut? I dont want to have a oil pump problem down the road?

 

[gofer]

So is stock gears better then straight cut? I dont want to have a oil pump problem down the road?

They're both stock DSM gears.

No matter what the application, whether you're putting straight cut gears in a 7-bolt front case or not, you NEED to blueprint, de-bur, detail, and clearance your oil pump/gears.

It's always buyer beware when assembling a motor to hold 3 to 4 times it's rated power output, and rev'ing 2k higher into the powerband while doing it, on a stock front case. My personal 2.3 was built by JAM (Jackson Automotive) and they won't even build a stroker without turned down BS's and helical oil pump gears. Believe me, I tried doing a BSEK and straight cut gears and they absolutely will not build a stroker without BS's.

The OP's question was what oil pump gears, helical or straight cut, should be ran with a BSEK. Tim Zimmer brought this to light, like I said earlier, when I was asking these questions and on his personal motor (2.3 with a BSEK) he's running straight cut gears and hasn't had any oil pump failures taking it to 8.5k and putting down over 800whp.

Do some research and read what others have suggested, speak with your engine builder, and then decide where your money is best spent.

Here's an example of someone running helical gears with the stubby shaft.

http://www.dsmtuners.com/forums/maintenance-repairs/433815-two-front-cases-two-blown-oil-pumps-has-anyone-ever-seen-before.html

 

[JusMX141]

Straight cut gears and OEM stub shaft are proven to 10K+ rpms. Wherever this theory of necessity to run a full rear shaft came from, I have no idea.

Straight cut gears are more noisy than helical, which is why Mitsubishi changed to helical in every year beyond 90. They don't care about durability because the 4G63 was designed with balance shafts and a factory rev limit of 7200....well within the capabilities of the helical gears.

If you're building a race engine, use an OEM stub shaft with OEM straight cut gears inside an OEM case and you'll never have problems. Ever. Problems only occur when you mix-and-match OEM and aftermarket poil pump parts, or listen to someone that has no idea what they're talking about.

 

[iceman510]

Only 6 bolt OE pumps are sold with the gears separate, all the 7 bolt pumps come with them included.

I agree with what Hal said. The case machining is different between the 6 bolt and 7 bolt cases. I personally would not run the straight gears in a 7 bolt case. Perhaps Tim Zimmer can provide detail on this combination if he recommends it.

 

[DSM_GSX01]

Ok thanks for all the info. Thanks for the link also. And i know both gear are OEM and i just was wanting more info on the rec limit? Also when installing straight cut gears you have to de-bur? I dont understand? I understand the rest almost.

 

[bigbird94]

So the "6 bolt" pumps are for helical gears only? Ive never seen a 90' specific pump.

 

[iceman510]

Only 6 bolt OE pumps are sold with the gears separate, all the 7 bolt pumps come with them included.

I agree with what Hal said. The case machining is different between the 6 bolt and 7 bolt cases. I personally would not run the straight gears in a 7 bolt case. Perhaps Tim Zimmer can provide detail on this combination if he recommends it.

OK, minor change to what I said earlier. There is a different case between 6 bolt straight gears and 6 bolt helical gears, then of course another different case for the 7 bolt. The helical gears for the 6 bolt and 7 bolt appear to be the same (MD174581/2), so they will fit both cases for 6 bolt and 7 that came with helical gears.

So the machining difference I cited is actually between the cases for the 6 both with straight cut gears and 6 bolt with helical gears.

Info attached.

 

[DSM_GSX01]

Ok i am going with straight cut gears in my pump. I did the balance shaft deleate so i think it will be a good. I am not sure if i will have a problem but bought the OEM stubby shaft.

 

[daren_p]

I run straight cut gears in my 7 bolt housing with BSE, based on the input of other experienced members. They will be a bit noisy when the motor is cold (sounds like the whine of a quiet supercharger) but once things warm up, I no longer notice them.

 

[DSM_GSX01]

Nice. I think it wont be to bad to notice. I notice alot of things if there is a different noise in the bay. The kit i got with the stubby shaft was from STM. The STM BSE kit.

 

[FirstCarIsA GSX]

OK, minor change to what I said earlier. There is a different case between 6 bolt straight gears and 6 bolt helical gears, then of course another different case for the 7 bolt. The helical gears for the 6 bolt and 7 bolt appear to be the same (MD174581/2), so they will fit both cases for 6 bolt and 7 that came with helical gears.

So the machining difference I cited is actually between the cases for the 6 both with straight cut gears and 6 bolt with helical gears.

Info attached.

You're claiming that there is a difference between front cases on the 6 bolts between the straight cut and helical gear sets? I've never heard of anything like this before and I know plenty of people running straight cuts in your average 6 bolt case. Could you elaborate on this a bit more?

 

[DSM_GSX01]

my 7 bolt has helical gears in it. 6 bolts have straight cut gears if i am right i hope. Let me know if i am wrong on any of this. Thanks

 

[mnim15]

A couple things I am wondering:
Are there any known issues with running helical gears in a case for straight cut gears?
Does running a turned rear balance shaft with straight gears provide no benefit?