Engine angle when using motor plates

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Engine angle when using motor plates

Post  t120r on November 27th 2016, 9:16 pm

Right now I have 2.5 degrees tailshaft down on the transmission. I do need to lift it up a bit though. Will a 0 degree angle be ok?

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Re: Engine angle when using motor plates

Post  rmcomprandy on November 27th 2016, 9:57 pm

t120r wrote:Right now I have 2.5 degrees tailshaft down on the transmission. I do need to lift it up a bit though. Will a 0 degree angle be ok?

Usually, anywhere from 1 to 7 degrees is fine as long as the u-joint angles are where they are supposed to be.

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Re: Engine angle when using motor plates

Post  DILLIGASDAVE on November 28th 2016, 4:45 am

If it's a drag-only car (no street/highway use) with an "aftermarket/no rubber bushings" type rear suspension (drag 4-link, or ladder bar) start with the car initially mocked-up sitting at the desired "race ready" ride height off the ground. Then point the crankshaft/tailshaft centerline directly at the pinion centerline, and point the pinion C/L directly at the crankshaft/tailshaft C/L.

This will give you an initial mock-up driveline U-joint operating angle/driveline operating angle at each U-joint & throughout the entire driveline of 0.00* (in relation to the whole driveline, and not in relation the ground). Then make your motor/mid plates & tailshaft mounts with the engine/trans sitting at this angle. Then when the car is finished and again sitting on the ground (and the driveline again sitting at 0.00*) you dial in/adjust in X amount of negative rear U-joint operating angle/negative pinion angle (in relation to the rest of the driveline, and not the ground) needed to offset any upward pinion rotation that might happen under launch loading.

The amount of negative operating/pinion angle needed will depend on what type "aftermarket/no rubber bushings" rear suspension you have. A drag 4-link might need anywhere in the -0.75* to -1.50* range, a ladder bar might need anywhere in the -1.00* to -2.00* range. Remember these "negative" pinion adjustments/settings are not in relation to the ground.
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Re: Engine angle when using motor plates

Post  t120r on November 28th 2016, 7:49 am

I should have specified that this is in a street driven '66 Bronco. My final engine/trans/tcase angle should sit about 2 degrees down at the tailshaft once I get it sitting where I like it best.

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Re: Engine angle when using motor plates

Post  kjett on November 28th 2016, 11:12 am

since it's in a bronco with a front axle, all the angles that were discussed for the rear, also need to be applied for the front. The 2.5* you have now will be fine and dandy. just make sure to check your pinion angles.
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Re: Engine angle when using motor plates

Post  t120r on November 28th 2016, 12:24 pm

Thanks for all the replies and info. Very Happy

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Re: Engine angle when using motor plates

Post  BOSS 429 on November 28th 2016, 1:56 pm

check the engine at the valve cover rail,with cover off. start there 1 to 2 deg down in the rear min. then check carb pad, then rear of trans.

make sure rockers of car/truck are at ride hight,and level as driven or all info is null and void
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Re: Engine angle when using motor plates

Post  DILLIGASDAVE on November 29th 2016, 4:48 am

If this is a street driven truck with decent ground clearance and using some form of a traction devise to limit pinion upward rotation under load (like Caltrak bars or "slapper bars" on leafspring combos) I think you might need to think about using a more street/highway friendly "equal but opposing" driveline profile method to help keep the U-joints happy & reduce the chance of vibration. An "equal but opposing" driveline profile means the crankshaft/tailshaft C/L angle (in relation to the ground) is parallel to the pinion C/L angle (in relation to the ground) while at the same time maintaining a positive (+) U-joint operating/mesh angle at the slip yoke C/L to driveshaft C/L, and a negative (-) U-joint operating/mesh angle at the driveshaft C/L to pinion C/L.

As an example, (and with the car/truck sitting with suspension compressed to the desired static ride height off the ground) if the tailshaft C/L was pointing "tail down" at say 1.50* (in relation to the ground), then the pinion C/L would be need to be pointing "nose up" at 1.50* (in relation to the ground) thus making them parallel to each other. This example's two U-joint's working operating/mesh angles then can be figured out by either installing the driveshaft and measuring it's C/L angle (off the ground) vs the 1.50* angles of the pinion & tailshaft. Or if you don't have the driveshaft handy just stretch a string between the tailshaft C/L & the pinion C/L and measuring the string's angle. Don't forget that driveshaft length can effect the U-joint's operating/mesh angles to some degree.

In this example doing all this in the end will tell you if the two U-joint's operating/mesh angles are too much (say over 3.5*) and could cause excessive U-joint binding/friction, or too little (say under 0.50*) at the example's 1.50* tailshaft C/L & pinion shaft C/L parallel angles. If the two U-joint operating/mesh angles were found to be too much, then you would drop the tailshaft more than the original example of 1.50* & raise the pinion nose more than the original example of 1.50*. But if the two U-joint operating/mesh angles were found to be too little, then you would raise the tailshaft more than 1.50* & lower the pinion nose more than 1.50*.
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