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Username Post: engine angle to frame or ground        (Topic#234850)
56chev66must 
Senior Member
Posts: 236

Reg: 04-07-04
02-02-10 07:52 PM - Post#1855253    

Hello All,

I did some research so I can check all of the angles of my drivetrain, and I discovered this: Everyone agrees that the engine is level when you put a bubble level on the carb mounting surface of the intake and the bubble level says its level.

But, people disagree on whether to raise/lower the frame to make it level and then check the engine angle, or to check the engine angle with the car sitting on the ground like it is when you are driving.

What say you?

56chev

 
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leon phelps 
Valued Contributor
Posts: 3378
leon phelps
Loc: Croydon Manor, PA
Reg: 06-04-05
02-02-10 08:55 PM - Post#1855300    
    In response to 56chev66must

I really doubt that everyone would disagree if you measured on the ground as in how you would drive or with the frame level.

The pinion and axle angle are only relevant when the car is moving, that would make the on the ground argument be the one that really mattered.

The same would be said for the carb angle. Why would you check carb settings for floats in a manner that would rarely be achieved, if only momentarily when hitting a bump or on a hill.
Metallica Fuel


 
Rick_L 
Honored Member
Posts: 25627

Loc: Katy, Tx, USA
Reg: 07-06-00
02-03-10 12:05 PM - Post#1855614    
    In response to leon phelps

Yes but the car bolts together irrespective of the ground.

I think they designed and built these cars with the intention of the frame being level to the ground at normal ride height. If you assume that, and set everything relative to the frame, you should be good.

 
55MAS 
Senior Member
Posts: 1219

Loc: North Coast, Ohio
Reg: 12-19-01
02-03-10 01:46 PM - Post#1855671    
    In response to Rick_L

  • Rick_L Said:
.... I think they designed and built these cars with the intention of the frame being level to the ground at normal ride height. If you assume that, and set everything relative to the frame, you should be good.



I agree with RickL but, the issue is whether the car in question maintains the factory stance or if it is owner modified (e.g., raised in rear or lowered in the front, big & littles, etc.) where the carb angle is changed.

There are two considerations, one being the drive system angles for proper universal joint operation, and second, whether the carb is level. If it even has a carb with floats to be concerned with.


 
Rick_L 
Honored Member
Posts: 25627

Loc: Katy, Tx, USA
Reg: 07-06-00
02-03-10 01:55 PM - Post#1855679    
    In response to 55MAS

There is another consideration for doing it like the factory did it. That's the clearance between the transmission/bellhousing and the floor. And that part rolls into other clearance problems if you alter it.

The carb will tolerate not being level. If it couldn't, you couldn't go up or down a hill could you?

 
55MAS 
Senior Member
Posts: 1219

Loc: North Coast, Ohio
Reg: 12-19-01
02-03-10 05:07 PM - Post#1855825    
    In response to Rick_L

They wouldn't be able to pull the front wheels at the drag strip either.


 
tewitt1949 
Contributor
Posts: 252
tewitt1949
Reg: 10-17-09
02-03-10 05:28 PM - Post#1855843    
    In response to 56chev66must


I am going through the same thing on my 56 nomad. After much research and trying to remmeber when I took my driveline course in college, the only thing you have to worry about is the angle difference between the trans output shaft and the yoke on the rear end. They have to be as close to the same as possable but no more that 3 degrees difference. It has nothing to do with the frame being level.
Here on a nother site it is discussed.
http://www.trifive.com/forums/showthread.php?t=386...

If you get one of the degree meters, put it on the output shaft of the tranny. Set the meter on zero. Then put it on the yoke and it should be less than 3 degrees. If not you have to figure out which way your rear end has to be tilted to achieve the correct angle. You can buy tappered shims at the auto parts store that goes between the spring and the rear end spring perch. I checked mine and I had to tilt the rear end yoke up. The shim I used was 1/4" thicker on the front than the rear of the shim. Hope this makes cents.

 
tewitt1949 
Contributor
Posts: 252
tewitt1949
Reg: 10-17-09
02-03-10 06:03 PM - Post#1855883    
    In response to tewitt1949


One thing I forgot to mention. You have to have the car weight on the rear axle.

 
Rick_L 
Honored Member
Posts: 25627

Loc: Katy, Tx, USA
Reg: 07-06-00
02-03-10 06:58 PM - Post#1855922    
    In response to tewitt1949

You are right about the driveline, except that 3 degrees is too much error. 1 to 1-1/2 degrees is more like it. You should also keep the u-joint angle below 3 degrees, 2 would be better, which is a separate matter.

But you don't want the engine/transmission installation far off from the stock installation for clearance reasons.



 
55MAS 
Senior Member
Posts: 1219

Loc: North Coast, Ohio
Reg: 12-19-01
02-04-10 03:35 AM - Post#1856119    
    In response to Rick_L

  • Rick_L Said:
The carb will tolerate not being level. If it couldn't, you couldn't go up or down a hill could you?



Since 56chev is checking his driveline angles he must have some modifications otherwise one merely needs to reassemble the components using factory correct parts and there is nothing to check since there is no adjustment feature in the GM installation other than replacing worn parts.

Obviously it has nothing to do with going up or down hills as you stated, which which seems to be your basis for indicating that it is not important.

Enlighten us on the basis at to why the GM engineers elected incline the carb mounting surface in relation to the primary centerline of the engine. This feature of the manifold cost some extra money to machine since there are other machined features on the topside of the manifold like the distributor seating and hold down threads and those of the thermostat housing which are perpendicular to the primary engine axis.


 
Rick_L 
Honored Member
Posts: 25627

Loc: Katy, Tx, USA
Reg: 07-06-00
02-04-10 06:06 AM - Post#1856152    
    In response to 55MAS

There's a paragraph in the old "Chevy Power" publication that explains that the tilt of the engine is to promote oil drainback. Makes sense to me.

 
acardon 
Senior Member
Posts: 9789
acardon
Loc: DFW TEXAS
Reg: 03-25-05
02-04-10 09:40 AM - Post#1856252    
    In response to Rick_L

I'm guessing, but I think the engineers may have considered other things, such as some u-joint angle is desired and to get the engine/oil pan as high as possible and keep the driveshaft tunnel as low as possible.
Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
Rick_L 
Honored Member
Posts: 25627

Loc: Katy, Tx, USA
Reg: 07-06-00
02-04-10 09:43 AM - Post#1856257    
    In response to acardon

It's all a package. Think about what you upset if you move one of the bricks.

 
tewitt1949 
Contributor
Posts: 252
tewitt1949
Reg: 10-17-09
02-04-10 10:48 AM - Post#1856288    
    In response to Rick_L


On my 56 nomad, I have a 327 engine using the factory front mounts. I also am using a 350 turbo and I have the tranny tail shaft as high as I can get it with out hitting the tunnel. My rear end is factory. When I checked the angle between tranny and the rear end, it was 3.7 degrees difference. To get it close to "0", I would have raise the tranny even more. But since I couldn't raise it any more, the only other option is to change the angle of the rear end houseing. I don't uderstand why it should be so far off since the front of the engine is at the factory heighth. I'm not going to change, but I wonder if I had used a factory 56 tranny using the side bell housing mounts, I wonder if the angle would be with in limits?

 
cdmhenry 
Very Senior Member
Posts: 2351

Loc: Minden, NV.
Reg: 09-14-00
02-04-10 03:05 PM - Post#1856453    
    In response to 56chev66must

  • 56chev66must Said:
Hello All,

I did some research so I can check all of the angles of my drivetrain, and I discovered this: Everyone agrees that the engine is level when you put a bubble level on the carb mounting surface of the intake and the bubble level says its level.

But, people disagree on whether to raise/lower the frame to make it level and then check the engine angle, or to check the engine angle with the car sitting on the ground like it is when you are driving.

What say you?

56chev





You may be overlooking an important measurement variable. Most V-8 intakes do not have the carb mounting surface parallel to the crank centerline (CL). It's usually tilted 1-2 degrees down at the rear. But that really doesn't matter.
The crank CL may be parallel to the line between the front and rear axle (and ground), but can be shimmed.
What you want to have is the driveshaft tilted down from the crank CL (or the output shaft CL) at the same angle the driveshaft is tilted up from the pinion CL.
Every Government Interference In The Economy Consists Of Giving Unearned Benefit, Extorted By Force, To Some People At The Expense Of Others - Ayn Rand


 
55MAS 
Senior Member
Posts: 1219

Loc: North Coast, Ohio
Reg: 12-19-01
02-05-10 03:56 AM - Post#1856753    
    In response to Rick_L

  • Rick_L Said:
There's a paragraph in the old "Chevy Power" publication that explains that the tilt of the engine is to promote oil drainback. Makes sense to me.



While driving up the mountains I always wondered why people back down the other side when decending the grade, so they don't starve thier engine for oil! Is that why people that live in the mountains park their Chevys "uphill"? So not to upset the GM design "to promote oil drainage". Factory, as well as most aftermarket oil pans, angle back toward the sump. This angle is in excess of the intake carb surface inclination. The engine has drains forward and aft to allow the oil to return to the pan.

I would not be afraid to drive down hill, or park my car pointing down hill for extended times, for fear of the oil not draining to the pan. That magazine statement "the tilt of the engine is to promote oil drainback" basically makes sense, but it is a bit silly when you think about it.

That fact that GM engineers elected incline the carb mounting surface in relation to the primary centerline of the engine cost some extra money to machine since there are other machined features on the topside of the manifold like the distributor seating and hold down threads and those of the thermostat housing which are perpendicular to the primary engine axis. Considering the cheapness and greed of the auto industry, it doens't make sense that the above feature is to promote oil drain back.


 
Rick_L 
Honored Member
Posts: 25627

Loc: Katy, Tx, USA
Reg: 07-06-00
02-05-10 11:45 AM - Post#1856941    
    In response to 55MAS

The "Chevy Power" book was something published by GM. Gives it a little more credibility than a newsstand rag. Maybe not much.

The first reason that the engine/transmission/drive hshaft runs downhill is for ground clearance along with what they considered an adequate depth on the oil pan sump.

The manifold has probably always been machined at the factory in a special jig anyway. The cost is negligible there, unlike it would be to set it up on a Bridgeport.

 
cdmhenry 
Very Senior Member
Posts: 2351

Loc: Minden, NV.
Reg: 09-14-00
02-06-10 11:30 PM - Post#1857781    
    In response to Rick_L

I recall that the primary purpose of the carb tilt and the oil pan tilt and sump position is flow of liquid under accelerwtion.
Pretty far off topic, The question is how to determine driveshaft angle.
Every Government Interference In The Economy Consists Of Giving Unearned Benefit, Extorted By Force, To Some People At The Expense Of Others - Ayn Rand


 
55MAS 
Senior Member
Posts: 1219

Loc: North Coast, Ohio
Reg: 12-19-01
02-07-10 04:26 PM - Post#1858118    
    In response to cdmhenry

Yeah it's off topic. Engine should be tilted so that carb surface on manifold is level when the car is sitting in stock stance. Then the engine is inclined (carb base level). The rear axle pinion is then adusted to the engine by measuring universal angles at the trans & differential. The topic went astray when engine angle was dismissed as being unimportant, talk of driving up and down hills, and oil drainage.


 
lrisner 
Forum Newbie
Posts: 11

Reg: 02-16-07
02-10-10 11:37 AM - Post#1859973    
    In response to 55MAS

There is an excellent article about on the Mark Williams site in the Tech Section.

 
tewitt1949 
Contributor
Posts: 252
tewitt1949
Reg: 10-17-09
02-10-10 05:26 PM - Post#1860215    
    In response to lrisner

http://www.markwilliams.com/driveshafttech.aspx

 
leon phelps 
Valued Contributor
Posts: 3378
leon phelps
Loc: Croydon Manor, PA
Reg: 06-04-05
02-11-10 07:26 AM - Post#1860561    
    In response to tewitt1949

I need to go up the mountains now so I can tune my carb. Too funny.

I have read less important or relevant things that manufacturers have said.

Oil drainback may be an issue, since the better oil manufacturers have gone to a remote sump. Shows that US manufacturers have not exactly been on the ball with the splashing around of oil that causes loss of efficiency. The forced filtration issue does not help their case either.
Metallica Fuel


 
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