Re: Engine installed angle ??
[Re: Torq37]
#3258431
09/17/24 04:32 PM
09/17/24 04:32 PM
|
Joined: Jan 2003
Posts: 11,028 Freeport IL USA
poorboy
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 11,028
Freeport IL USA
|
The factory motor angle was 3 degrees, rear down (when the carb base on the intake was level). The carb base on the intake is cut at the 3 degree angle, so the rear of the motor was slightly lower. But, that was based on the car sitting level as well.
If the rear end is jacked up, and the front is not (or the front is jacked up and the rear is not), the motor angle will be different if measured in degrees from level. The end goal was for the rear of the motor to be slightly lower then the front, and that the carb be level, front to rear, and side to side, as the motor sat in the car. Those things are not as important these days as they were back when the process was first started.
|
|
|
Re: Engine installed angle ??
[Re: Scatpak]
#3258525
09/18/24 07:37 AM
09/18/24 07:37 AM
|
Joined: Oct 2005
Posts: 9,208 Ontario, Canada
Stanton
OP
Don't question me!
|
OP
Don't question me!
Joined: Oct 2005
Posts: 9,208
Ontario, Canada
|
Sounds like your moving along good. Is the body done and painted? Oh yeah. Car's been back for a couple months now. The rear end, and tank are in, the rear lights and bumper are on. The fuel and brake lines are all run. The engine has been fired and is sitting on a cradle ready to go in from below. I have one more small chore to do on the engine by the end of this week and it will probably go in next week. Need to find someone to install the headliner then I can get the interior in.
|
|
|
Re: Engine installed angle ??
[Re: Stanton]
#3259049
09/20/24 02:04 PM
09/20/24 02:04 PM
|
Joined: Jan 2003
Posts: 5,813 Detroit area
6PAX
master
|
master
Joined: Jan 2003
Posts: 5,813
Detroit area
|
I'm using a digital level, awesome thing - it measures in tenths of a degree - don't buy one if you have OCD !! Anyhow, you can't just measure at the tailstock, you have to measure at the pinion as well. Both angles play into the equation. Since the front angle is pretty much fixed, adjustments will have to be made (if necessary) at the rear with wedges or whatever. But keep in mind that raising or lowering the car with wheels/tires does NOT change the angles relative to each other. The ONLY thing that will affect the angles is raising or lowering the rear end in the chassis. I did buy a digital level. I had borrowed a friend's dial type angle gauge but my vision is so crappy I couldn't make out the hash marks on it. The digital gauge is great as it is easy to read. Anyway, yeah, I understand the tailstock and pinion need to work together. I was just wondering about the tailstock angle being only .6 degrees downward rather than 2 or 3 degrees now that I have the larger tires on the car. I adjusted the pinion up to a positive .6 degrees to be parallel to the tailstock and then dropped it back down 2.5 degrees so it now has a 2 degree below level downward tilt. I did 2 1/2 degrees as I read 2 to 3 degrees was good so I just put it in the middle. Then I tightened the u-bolts to lock it in. I hope this is right as I have a welder coming over sometime in the near future to weld the perches for me.
|
|
|
Re: Engine installed angle ??
[Re: 6PAX]
#3259092
09/20/24 08:08 PM
09/20/24 08:08 PM
|
Joined: Jan 2003
Posts: 11,028 Freeport IL USA
poorboy
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 11,028
Freeport IL USA
|
So, we need to be sure everyone is on the same page here, so to speak. The motor angle in the car, and the angle the carb base is cut on the intake are entirely different then the pinion angle of the rear end.
We need to view them as two different things, because they are.
The motor angle was originally set up so the carb base can be level so the floats, jets, and passages work the best, and that would be what is considered to be "level with the earth" or matches up with the little bubble between the lines on a level. that level is both for front to rear, and side to side. Way back when, somewhere in the 40s, the engineers determined they wanted the motor to sit in a car with the back of the motor slightly lower then the front of the motor. I have no idea how, who, or where the 3 degrees lower in the back then the front came along, but that was the number everyone seemed to agree upon. in order for the motor to have the rear 3 degrees lower then the front, and still have a level carb, that meant that the carb base had to be milled with the front 3 degrees lower then the rear. Those carb bases have been cut at that 3 degree angle since my dad was a kid. All I know is the carb base was cut so the rear of the motor could be 3 degrees lower then the front, and the carb was to be set level.
The rear pinion angle doesn't really have anything to do with earth level, or the little bubble between the lines on a level. the rear pinion angle is the relationship between the center line of the transmission main shaft, the center line of the drive shaft, and the center line of the pinion shaft in the rear end. Because the center line on the transmission is generally locked into position in the car with motor and transmission mounts, its considered as being fixed and does not move. The rear end, on the other hand, is attached to springs and brackets that allow it to move about. The poor drive shaft has to stay connected to both the fixed end, and the moving end. Its able to do this through the use of universal joints (U joints), and a spline shaft someplace in the driveshaft. with both ends of the driveshaft connected to the U joints, the varying angles between the fixed end and the moving end are split equally between the two U joints. Because the two U joints are operating at the same angles all the time, they cancel out harmonicas and balance issues, but those U joints have a limited amount of movement before problems occur. The rear axle is the biggest problem. Not only does it move up and down with the suspension, it also wants to rotate with acceleration, and rotate the other direction with braking. Usually if the suspension travel is within the U joint's allowed movement, the u joints and the spline shaft accommodate suspension movement well. Often times, the rotation caused by braking is not done when the driveshaft is under a load, so the U joints can handle that as well. The biggest issue is the rotation under acceleration. Generally, the rear axle wants to rotate up under acceleration, and that is usually when the highest stress in on the U joints as well. engineers have come up with a way to assist in that problem area, the concept isn't hard, but the process of getting it straight is.
So in a car, most of the time, the transmission main shaft and the pinion shaft are not in line with each other, one is higher the the other, and may be set off to one side or the other.again, there are limits, but generally the U joints can handle those different levels. For the explanation, lets assume that the transmission is higher up off the ground then the rear end is (most cars are this way). For everything to work, the center line of the main shaft in the transmission and the center line of the pinion shaft in the rear end have to be parallel with each other. they don't have to be inline, but they have to be going the same direction. One can't be running up hill and the other down hill, or one can't be running towards the left and the other running towards the right (anything more then 4 to 5 degrees is going to start tearing stuff up). In that the case, the drive shaft would have to bend and unbend every 1/2 revolution. Multiply your rear end gear x the motor rpm to see the problem that is going to cause. So, on the car with the transmission higher off the ground then the rear end is, it should be pretty obvious there is going to be a degree setting at each U joint that puts everything at its best location. That would be the pinion angle set at zero degrees. Now , with everything right, we climb into our racer and mash the gas pedal. the front end of the pinion where the U joint is at wants to rotate up. If we exceed that 4-5 degree limitation, we have just created the problem of trying to bend the drive shaft every revolution. We know the pinion wants to rotate up. If we set the U joint end of the pinion down 3 degrees from that zero position, we reduce the chance of exceeding the the 4-5 degree limitation (because we have added 3 more degrees it can rotate) before we begin to bend the driveshaft. The 3 degrees down on the pinion angle refers to the degrees we rotate the axle pinion shaft down from the perfect parallel position to the transmission main shaft center line. On a mostly street driven vehicle, 3 degrees down is probably not necessary, 1 or 2 degrees is probably good enough.
Another thing that really messes guys up is they measure the transmission main shaft angle off the end of the output shaft, then turn around and measure the angle on the pinion shaft across the u joint location on the axle with a magnetic angle finder. If you do that, you need to be sure the magnetic angle finder is facing the same direction when measuring both. If the magnetic angle finder is facing the rear at the transmission, and facing forward on the rear end, your angles won't agree, your going to have to do math to have the correct angle.
Also, the angle measurements have to both be made with the weight of the car on the rear end.
One more thing. raising or lowering the rear end in the car may change the angle the drive shaft operates at, but it does not change the pinion angle unless it rotates the rear axle. The only way to change the pinion angle is to rotate the rear end on its mounting brackets or change the length of the control arms.
|
|
|
Re: Engine installed angle ??
[Re: varunner]
#3259277
09/21/24 11:47 PM
09/21/24 11:47 PM
|
Joined: Jan 2003
Posts: 11,028 Freeport IL USA
poorboy
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 11,028
Freeport IL USA
|
You are correct, IF the motor (and everything else) is actually sitting at earth level in the car. A magnetic angle finder will always give you the angles based from a level earth perspective. If you have the back end of the car jacked up with the rear axle supported on jack stands, how will you know if the motor is still at earth level?
The pinion angle is always difficult to explain when a guy gets under the car with the body jacked way up at the rear (or front), or in a car where the motor isn't level.
Pinion angle always has to be thought of as the relationship between the transmission main shaft center line, and the rear axle pinion center line, through measurements of both. The zero starting point to set the pinion angle is when the trans main shaft and the pinion shaft are the same number of degrees off (earth) level in the same direction. Lets say those same real measurements in degrees are 5 degrees up (or down) from (earth) level. As far as the pinion angle is concerned, when both those measurements show the same degrees in the same direction, that is the zero point. Then you rotate the pinion shaft down the 3 degrees.
If you assume that the motor is sitting level in the car and its not, that will give you an incorrect pinion angle. The only way to set the pinion angle is by measuring the actual angles of the trans main shaft and the pinion shaft, establish their matching point, then roll the pinion down 3 degrees.
|
|
|
Re: Engine installed angle ??
[Re: Stanton]
#3259451
09/22/24 10:26 PM
09/22/24 10:26 PM
|
Joined: Jan 2003
Posts: 11,028 Freeport IL USA
poorboy
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 11,028
Freeport IL USA
|
DO NOT use the carb base in the equation. The only reason "carb base" has been mentioned is because most are cut at a 3 degree, angle so the assumption is the engine crank centerline has a 3 degree down angle. The simple fact is you want to measure and adjust the relationship between the crank centerline (trans output shaft) and the pinion. - with the weight of the car on its wheels so that the rear end is at ride height. YES! THIS ^^^ . DO NOT rely on what you think the motor position is to set the pinion angle. Measure everything where the ends of the drive shaft connect to the transmission and the rear end. Take one set of degrees off the flat end of the transmission tail shaft (not the transmission housing, the actual shaft the drive shaft yoke slides over) .and the other measurement off the the pinion shaft (the yoke the drive shaft bolts to is good enough as long as you use the machined surfaces where the U joint bearing caps are bolted in.
|
|
|
|
|