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Leveling Out an RB25 Engine Before Fabbing Mounts


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Hey all, quick question that I'm having trouble finding the answer to. I'm about to fab up the engine mounts for my RB25 and I've read online somewhere sometime ago that I needed to level out the engine using the flat flange on the bottom for the oil pan. That makes sense to me, but when I try to twist the engine to be flat it pushed my transmission shifter into the passenger's side of the trans tunnel.

 

is it better to go off of the transmission shifter and get the exactly flat or to go off of the bottom of the oil flange?

 

Also, I know that the oil pan has a bit of an angle on it, around 3 inches deeper on one side. Is this to flatten out the bottom and the engine actually should be angled a bit? I'm hoping somebody may be able to walk out and snap a few quick photos of their setup and describe it a bit. Thanks in advance!

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I would concentrate on matching up the driveshaft angles, if those aren't perfect or close to it the car will be un driveable.  You may have to lower the diff or tip it one way or the other and angle the engine/trans to point at the diff.  When your drive shaft angles are perfect then that is when you start making the engine mounts,  at least that is the way I do it.

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The side angle should be about 10 degrees toward the exhaust side. I lined up the L28 and the RB side by side they have about the same lean angle, just opposite directions. I would assume it's to give more room for the intake as the exhaust doesn't need as much room. My engine is about 2.5 degrees down. I found that there wasn't enough room in the tunnel to get it level, not without lowering the engine way down in the bay. The rear diff has an upward angle to match that, dont know the exact angle as mine isn't the factory diff, it's a short nose R200.

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5 hours ago, grannyknot said:

I would concentrate on matching up the driveshaft angles, if those aren't perfect or close to it the car will be un driveable.  You may have to lower the diff or tip it one way or the other and angle the engine/trans to point at the diff.  When your drive shaft angles are perfect then that is when you start making the engine mounts,  at least that is the way I do it.

Good points, I'll make sure and get that correct first. 

 

3 hours ago, bunkhouse said:

 As I understand driveshaft angles, the most important thing is to be sure the front and rear angles are the same.

Meaning that the engine  pinion or whatever is angled to point directly at the rear diff, and vice versa?

 

1 hour ago, winstonusmc said:

The side angle should be about 10 degrees toward the exhaust side. I lined up the L28 and the RB side by side they have about the same lean angle, just opposite directions. I would assume it's to give more room for the intake as the exhaust doesn't need as much room. My engine is about 2.5 degrees down. I found that there wasn't enough room in the tunnel to get it level, not without lowering the engine way down in the bay. The rear diff has an upward angle to match that, dont know the exact angle as mine isn't the factory diff, it's a short nose R200.

ok perfect, just ot make sure I am understanding, your RB oil pan isn;t level at the flange, but the driver side is lower than the passenger side? and 2.5 degrees meaning your transmission is lower than the engine, correct? Thanks for the help, I appreciate it! 

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15 hours ago, Jboogsthethug said:

ok perfect, just ot make sure I am understanding, your RB oil pan isn;t level at the flange, but the driver side is lower than the passenger side? and 2.5 degrees meaning your transmission is lower than the engine, correct? Thanks for the help, I appreciate it! 

Yes. 10 degree lean toward the driver side (left) and 2.5 degree down to the rear. Do measure your pinion angle and match it.

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Here are a couple really good articles covering driveline alignment and pinion offset, for anyone who sees this in the future:

http://www.rustynutscarclub.com/driveline.htm

 

Note: This article mostly applies to build out the rear end but has some good info as well for aligning driveshafts.

https://www.dragzine.com/tech-stories/pinion-offset-guide-and-how-to-with-chassis-engineering/


Even more on pinion angles:

http://www.wolferacecraft.com/pinionangle.aspx

https://www.hotrod.com/articles/91758/

https://www.quickperformance.com/Pinion-Angle-Measurement_ep_45.html

https://www.hotrodhotline.com/setting-pinion-angle

http://www.superchevy.com/how-to/transmission/1502-how-to-use-tremec-driveline-angle-finder-app/

Edited by Jboogsthethug
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2 hours ago, grannyknot said:

This is a great gadget that wish was around when I first started swapping engines, it saves a lot of time lying on back under the car.  Digital inclinometer,  don't buy the $13 ones, just crap, $25 and up for a decent one.

 

 

71B8hm8VwLL._SY450_.jpg

I can imagine the digital gauges that have popped up in recent years must be a lot better/easier to use than the old tools! Thanks for the tip, i'll look into getting one

 

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Also, I talked to @stony about his old RB swap via FB and he shared this with me : "I have to see a picture of the pan again but I believe the bigger part of the sump needs to be level and then the shallow part of the pan has a tilt to it. I've actually seen people mount the RB straight up and down with no issues I believe they put a drain in the back of the head though"

 

I thought that was interesting and good info. Also, @winstonusmc, I measured the pan based off what stony said and it was 11 degrees, you were pretty spot on! 

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  • 2 weeks later...
  • 3 months later...

Lots of good info here.

Some theory is also, depending on how solid your diff mount is, sometimes they have the diff slightly more nose down (1/2-1*) so that under load it straightens up to match angles. You can also play with diff angles by 1) moving where the washers are around your mustache bar (can put poly directly against chassis to raise rear of diff and level it more), or 2) putting washers between your diff mount and the diff (if it's stock mount, the more washers to more nose up it gets). You get the idea.

 

 

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  • 2 weeks later...
On 2/12/2019 at 1:05 PM, Jboogsthethug said:

@winstonusmc I found what I think is your YouTube channel randomly, is this you?

 

 

 

also, what tuning software are you using?

 

Yeah, that's my channel. That is Tuner Studio for Megasquirt. It's the registered version that has the custome dashboard layout.

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  • 1 month later...
On 2/24/2019 at 7:31 PM, winstonusmc said:

Yeah, that's my channel. That is Tuner Studio for Megasquirt. It's the registered version that has the custome dashboard layout.

I never replied, thanks for the info! I'm going to have to download that and learn how to use it when I get my Z running! Awesome!

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  • 1 year later...
On 9/30/2018 at 2:12 PM, Jboogsthethug said:

 

This thread is full of fantastic information...thanks for all of your research!

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