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Discussion Starter #1
Hello, I have a few questions for you all.

I have a 429 I’m going to put into a Fairmont. I am running front and mid plates. So here is a little background info.

First of all, I put the car on jackstands and set the rear end to the correct ride height. I then adjusted the pinion angle. After that I placed the engine and trans into the engine compartment and put it basically where I wanted it (actually where it fit the best). Note: I am running a factory K-member with no spacers. I used a laser pointer to point the trans right at the pinion.

Here are my questions:

1 Since a 9inch rear end has an offset pinion is it correct to “aim” the transmission output shaft at it? By doing that my engine is not centered in the engine compartment but angled ever so slightly.
2) Should the engine be level, or is it OK to have it sticking in the front a little bit (angled up)? I don’t think I can level the engine with the stock K-member and the shape of the trans tunnel. I already modified the trans tunnel a bit, but I would need to really modify it a lot more to be able to raise the trans up to lever the engine out. And if I did that the trans output shaft would no longer be pointed directly at the pinion.

So that’s basically what I’m up against. This is the first time I’ve ever done this, so I’m happy to hear any suggestions. I would prefer to use the stock K-member without spacers if possible. Nothing has been welded in place so any of this can change. I am running a supercharger that is going to be sticking through the hood, so hood clearance isn’t an issue, but I don’t want the engine to be noticeably offset or not centered.

Thanks.
Wes
 

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Wes:

Just as Damon said, your engine will be offset to the pass. side a bit in order to clear the steering shaft.

The most important thing to remember is to get the centerline of the engine/trans combo parallel with the C/L of the pinion shaft in the rear end. If not, the ujoints will wear out quickly.
 

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aa

On the horizonial plane the crank shaft should not aim at the pinion yoke, like it was pointed out by the guys above it needs to be parallel with the rearend pinion centerline(looking from the top of the car)

The same holds for the pinion angle (looking from the side of the car) the crankshaft transmission output shaft has to be parallel with the rear end pinion shaft.

Very difficult to explain but if the parallel issue is not observed the incorrect angle causes the driven pinion to run faster and slower than the crankshaft in relationship to the position of the U joint.

Pinion angle is misunderstood by most: First the crank centerline and rear end pinion centerline need to be parallel for optimun energy transfer. Both from the horizonial (looking from the side) and vertical planes (looking from the top). Once this is established you are redy to set "Pinion Angle"

As the tires turn down under acceleration the pinion tries to move up as the rearend twists. How much it turns up depends upon the rear suspension, leaf spring cars twist big time, and 4 link and ladder bar cars twist very little. So to set "Pinion Angle" you first adjust the pinion shaft to be parallel to the crankshaft centerline looking from the side. Now you adjust the pinion down several degrees. The result is that when the rearend twists at launch, the pinion moves back up and makes itself parallel with the crank again. I believe 4 link and ladder bar cars normally use like a 2 degree negative pinion angle (as related to the static setup) , leaf spring cars more like 5 degrees. I am sure some chassis type folks can correct me if I am off on the degrees.
 

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aa

Right on, a picture is worth a thousand words

And ujoint phasing is important - if off just a little, you get big time vibrations (in a 2 joint shaft it is the relationship of the front to the back joint)
 

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Re: aa

rvesterby said:
On the horizonial plane the crank shaft should not aim at the pinion yoke,
That's not always true. There are indeed situations where you do want to point the crankshaft/trans tailshaft centerline directly at the pinion yoke's centerline while the car is at rest sitting at ride height. This would be faster "drag strip only" cars (that will never/must never see street/highway use) that have aftermarket suspensions like full chassis cars & some back-half cars.

The street/highway use style of "equal but opposing" U-joint geometry (parallel geometry) that you mentioned where the crank & pinion C/L's are on parallel planes to each other while the U-joint operating angles are (at each end of the driveshaft) at the same (but opposing) angles does work for a lot of vehicles. But on higher HP faster cars with very little pinion operating angle to begin with (in the range of only -1*, -1.25*, or -1.5* it's better to point the crank directly at the pinion so the front slip yoke U-joint has an operating angle of around 0.0* to the driveshaft (plus or minus 0.5*). This is done so that during the launch with chassis flex, pinion rotation, (and etc,etc) all of the U-joint operating angles are as close to 0.0* as possible during the launch loading to reduce the parasitic drag as much as possible. But as I mentioned while this setup is used on faster strip only cars, the "drag race only" operating angles must NEVER be used on any car that will ever see any street/highway use.
 

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aa

rvesterby wrote:
On the horizonial plane the crank shaft should not aim at the pinion yoke,

Dave I was referencing the horizonial plane or looking down from the top of the car.

Sounds like you were referencing the vertical plane or looking from the side of the car as you referenced static height and launch ( "This is done so that during the launch with chassis flex, pinion rotation, (and etc,etc) all of the U-joint operating angles are as close to 0.0* as possible ")

Launch does not effect the horizonial setup just the vertical as it rotates on that axis. I agree if you can point the crank and have the pinion point back that is ideal in the vertical plane. Because as you stated there is zero U Joint angle with no parisitic lose. And that is a parallel situation, just no offset in the centerlines.
 

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Re: aa

rvesterby said:
Dave I was referencing the horizonial plane or looking down from the top of the car..
Sorry about that, I thought you were talking about viewing it from the side. :oops:
 

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Discussion Starter #10
Thanks for all the responses. I really appreciate all the help from you guys. Now I’m really confused!! HAHA. Kidding. It makes perfect sense that the CL of the engine and pinion should be parallel in both the horizontal and vertical planes.

I do have a few more questions.

1. This is going to seem like a really stupid question, but I’ll ask it anyway. I assume the 0 degree pinion angle is in relation to the ground, irregardless of what the car’s stance is correct?

2. While I am doing all this setup work, should I have the pinion angle set to 0 degrees, then when everything is said and done set the pinion to 2-3 degrees “down”? I am running a stock style Fairmont rear suspension but with adjustable upper and lower control arms with polyurethane bushings.

3. I am using an angle finder that measures in 1 degree increments, which means I can estimate to .5 degrees. Is that accurate enough for this?
 

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aa

When Dave was referencing Zero degrees he was talking about the difference in degrees between the output transmission flange and the pinion flange.

Say the trans sloped down and you measure 5 degrees off the the output yoke. Then you measure the pinion flange and it slopes up by 5 degrees.
Regargless of if they are perfectly aligned or the centerlines are parallel you will need to adjust the pinion down a couple degrees so it measures 3 degrees. So now when the axle rotates up at launch in theory the bushings compress and you have your Zero degree difference between the output and input flanges - as the flanges are at 90 degree angles to the centerline

Sounds like you have it figured out

The measuring of the flanges is relative to each other regardless of if the car is setting level or not

Yes that is accurate as needed - We all take the word of someone who has proven this as the basis of 2 or 3 degrees down. In reality how much difference does it really make I am curious, does it make you lose 10 hp to the rear wheels if you dont rotate the pinion a couple of degrees - I have never read any papers that addressed this. Maybe Dave has some input. But in heads up racing like Pro Stock where every .01 ET you gain is significant and .001 is worth looking for they probably know the answer.

Dave Morgan used to write a column for Nationial Dragster, these were the kind of questions he liked to answer.
 

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What type of effect does pinion angle have on the car other than in terms of Hp & pinion life?

So, for the time being as we build the I can use these steps?

1. Set the car & axle at ride height.
2. Make sure the engine / transmission centerline is parallel to the pinion center line in the horizontal and vertical planes.
3. For a base setting make sure the pinion angle is 0 degrees. In relationship to the engine / transmission. (This is if you are using upper and lower adjustable control arms.)
 

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Re: aa

rvesterby said:
Dave Morgan used to write a column for Nationial Dragster, these were the kind of questions he liked to answer.
The only problem with some of the ND "guest author" tech/how-to articles is that over the years a bunch of them sounded more like a running advertisement or infomercial, and not helpful tech articles. Dave Morgan's articles were always damn good, as were Rick Jones's. Both Dave & Rick offered useful chassis tech insight instead of just doing like some other writers & bashing you over the head with "buy my crap" bullshit articles.


jones said:
What type of effect does pinion angle have on the car other than in terms of Hp & pinion life?
As always, the idea of using "pinion angle" as a chassis tuning tool is a bad, bad idea. The only real-world "physical" effect it can have on tuning is if you dial in so much operating angle that you cause U-joint binding under launch loading. And any U-joint binding is just asking for a U-joint to fail & exit the car with the driveshaft.

On a street car the U-joints are expected to last "forever" and they pretty much do when compared to a race car. For a long life U-joints need some amount of operating angle misalignment so that the roller needle bearings don't pound on the exact same spot of the U-joint's cup & shaft over and over again millions & millions of times as you drive down the street/highway. But this misalignment can cause unwanted parasitic drag in a race car which is why your shooting for 0.0* operating angles in a drag only car (under loading during the launch). This can shorten the life span of U-joints on a "drag only" car. But for drag racing U-joints should be thought of as a scheduled "throw away" maintenance item, just like slicks, oil, or rod-ends are.


I drew up some more slip yoke-to-driveshaft-to-pinion diagrams dealing more with the relation of the engine height to the tire diameter (crank nose up vs nose down), I will post them late tonight if I get a chance.
 

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These are generic over-exaggerated drawings to point out a few different possible ways that a motor/trans might be hung (nose-up, level, nose-down) in different types of cars.

The examples show how the engine might sit when factoring in different types of "intended use" (street vs strip only), or the different crank nose heights of different chassis (because of different front suspension types), or the different diameters of slicks (which controls how high off the ground the pinion will be).







MS Paint & Photoshop are fun toys.....
 

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Question.

I tried asking this question but none of you answered so I will just bump this one up! :lol:

Being that you can always rotate your axle. What is better to have the engine installed? Engine level with the ground or carb pad level?
What type of tollerance should I strive to hold?

Here is a link to my pictures just incase. They will show you how I am going about doing this. http://www.460ford.com/viewtopic.php?t=23308&start=90

Right now I have the engine real close to this setup.

PS. Then again I could be missing something! :lol:
 

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Jones,

Generally speaking while it would be nice to always have the "choice" of how to hang the engine (in reference to crank "nose up", crank level, or crank 'nose down" angles) in every type of drag car, usually (unfortunately) the body/chassis/front suspension type & rear slick diameter most times will dictate how the engine angle will have to sit in order to clear steering/suspension and also line up with the rear pinion. So a lot of the time (depending on the car/combo) the engine crank angle position ends up being less & less a "personal choice" and more the type car/chassis/combo basically chooses crank angle for you.

As an example, say you had a mini-tubed Fox body sitting at "normal" ride height that had all stock front & rear suspension points & geometry, plus a 27 -28 " tall slick so the pinion is close to the ground. It would be very hard to install the engine with the crank pointing "nose down" (at say 9.5 to 10" off the ground) in this car and still be pointed at the pinion without reworking a lot of the front suspension.

Another example. Say you had a low slung full chassis car with a tall slick around 33 to 34" tall so the pinion is going to be a decent height off the ground. And say for some reason you wanted to install the engine in this car really high off the ground in a crank "nose up" position (while still pointed correctly at the pinion). You would end up with an engine sitting in a position where the valve covers (& possibly part of the heads) might be sitting above the hood-line.

Some times you can choose the crank angle because circumstances allow you to. And some times circumstances dictate the angle things have to be.
 

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I figure I will use a 28" or 29" tire, but I have not taken this into consideration so far with what I have done.

So far I am using the 7.5 axle as reference and sitting the car on the stock suspension in the rear.
I jacked the car up and used the body seam along the rocker panel as point of reference for leveling the car out.
As you mentioned there is not a whole lot of wiggle room between the steering rack and transmission tunnel. But if I need to com down in the nose some more I can always use the offset steering rack bushings.

I figure that the 7.5 and 8.8 will sit in the same position. Then if the pinion angle is off once I get the car completely built I can use the adjustable upper and lower control arms to adjust the pinion angle.

Am I setting myself up for disaster doing it this way?
 

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While some aftermarket 4-link bars for a Fox body might have a decent amount of adjustability, you definitely want to get things as close to where they need to be during "ride height" mock-up so you have plenty of usable adjustment range left to tune with after the car is done.

Don't know the physical differences between the 7.5 and the 8.8 stuff, but if your sure they are close to being the same then the 7.5 could probably stand in for the 8.8 just fine for mock-up. Just as long as they both have the same angle the pinion meshes with the ring gear (hypoid angle), and both have the same pinion length from axle C/L, then the rear U-joint should be sitting in the same place with either housing.

You definitely want to mock-up "everything" (engine/trans height & angle, both U-joint to driveshaft angles, & the housing/pinion angles) with the rear housing sitting at the proposed "ride height" measurement in relation to the body/chassis. Remove the springs if that's what it will take for you to compress the suspension/housing to reach the proposed mock-up ride height while on jack stands.
 

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I worked on it some more this weekend.

Right now as the car sits on the rear suspension, with the body seem level. (A) The rear pinion is sitting down 3 degrees. (B) Engine center line is sitting nose high 3 degrees.

I tried pulling the crankshaft centerline down 3 degrees but the transmission yoke hits the floor board. Then if I try to bring the entire engine down it hits the steering rack.
I was thinking if I could get the engine centerline at 0 degrees it would be a good thing.

I have three options. I can install offset bushings on the steering rack, cut out and raise part of the transmission tunnel, or just leave the engine centeline at 3 degrees.
 

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Just remember that the angles you are mentioning are referenced off the ground, making them ONLY the reference points and not the actual U-joint's operating angles.

You need to factor in one more piece of the puzzle to actually be able to figure both the front & rear U-joint operating angles.....the driveshaft angle it's self. Knowing some of the current angles in reference to the ground is important info during mock-up (like crank nose-up 3* + pinion nose-down 3*). But you also need to know what the driveshaft angle is doing as well (especially as you move the crank centerline around) to figure the operating angles.

Keep after it.
 
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