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    1. #1
      Join Date
      Sep 2006
      Location
      Chicago
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      355
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      correct engine angle?

      I 'm installing an ls engine in a chevelle what angle should the engine be at from front to rear? Any help greatly appreciated



    2. #2
      Join Date
      Dec 2002
      Location
      Lost Wages, Nevada
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      2,684
      Country Flag: United States
      Engine and Pinion Angle: There has been numerous "hear says" about what the pinion angle should or should not be. Hopefully this will clear up a lot of misconceptions. One of the biggest misconceptions is the engine angle is it is relative to the frame. Engine, pinion angle and ride height is all relative to the ground.

      Most engines are set at 3 degrees, when you look at the side of the intake manifold on a carburetor engine you will notice the manifold has an angle in it. This angle is to allow the carburetor to sit level. I have heard many reasons to why this is done... but the main purpose of having an engine angle is for the u-joint misalignment and its associated rotation. I have even heard that it is to allow for more room in the passenger compartment by having a smaller tunnel... and this is why the car manufacturers build front engine cars with the engine at an angle. Many drag race cars have a 2 to 3 degree negative engine angle, (engine down in front.) Having this negative angle allow for better weight transfer to the rear of the chassis. The 3 degrees you keep hearing about is the recommended angle for carburetor cars with intake manifolds set at 3 degrees. With the engine and pinion set at 3 degrees they do not line up directly and requires you to make them parallel. This misalignment allow the u-joints to rotate on a street car. Personally, I believe that the requirement of being parallel has more to do for the suspension articulation/travel, as well as for misalignment for the joint operation. It provide's a range in which the joint can work without going into bind.

      There is another misconception regarding the pinion angle on drag cars. I have seen many people advise that the pinion needs to be 2 - 7 degrees down. In relation to what? I disagree with this theory and set-up. The pinion needs to be "parallel" to the engine angle or in a straight line for the least amount of horse power lost. This following is a quote from Mark William's web site:

      "There is a general misunderstanding about "dropping the pinion down" several degrees. This is a practice that could be applied only to leaf spring cars without any traction control devices where springs can wrap and change pinion angle. This practice would not apply to 4-link, ladder bar or torque arm equipped cars. Failure to maintain matched and minimum operating angles increase erratic non-uniform output velocity from the drive shaft to the differential."
      In a dragster, you can set up the engine angle at almost any degree just as long as the transmission is perfectly inline with the pinion yoke. However, when the engine and pinion yoke is in direct line, it does not allow for the rotation of the u-joints. This straight alignment is mostly used on drag race cars.

      If you would crawl under your car and look at the pinion angle you will notice it is the same angle as the engine/transmission (they are parallel). A good example of having negative engine/pinion angle is when you lower a 1 ton crew cab where you lower the front more than the rear and there is quite a "rake". In this case you have to put a wedge on the back side of the spring perches to correct the pinion angle down.

      If you are building a chassis you need to first determine ride height. This is the most important thing you need to do. Decide what wheels and tires you want to use before you pick up the welder. If a chassis builder does not ask you what tires you are going to use do not buy from him. How can he build your chassis without knowing the tire diameters? How can he set up the front end and engine angle? What they do is build a chassis based on what they want or think you should have and not what you want.

      Now... determine the ground clearance you want for your oil pan. Set your motor mounts based on this and the angle that best fits your car. Try to set the pinion parallel to the engine angle. Before you weld the brackets on the rear end housing be sure that the rear end was set at "ride height" (ride height is where the rear end would be with the car done.)

      If you find a chassis builder that says you have to have the engine angle at 3 degrees and there is no other angle you can set if at, find another cat to do the work. He apparently does not understand the principles of setting correct engine and pinion angles. Also, no chassis builder can build you a chassis with an optimum suspension geometry without knowing "proper" or the "designed" ride height.

      Hope this might help...

    3. #3
      good post. I agree.


      Jason
      Bringing innovation into the industry one build at a time!

    4. #4
      Join Date
      Jul 2002
      Location
      Mesquite, TX
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      4,936
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      Interesting, thanks Chicane.

      I can see that most carb engines would need to either have 3 degrees down at the back to keep the carb level, or modify the manifold or spacer to keep it level... but for a FI PT setup (where tunnel size is not a concern), would you suggest something along the lines of the -2/-3 degree drag setup, or less than that since we're not all about going in straight lines?

    5. #5
      Join Date
      Sep 2004
      Location
      Chicago - western burbs
      Posts
      673
      I agree that the absolute angle of the engine is irrelevant, but there are other relationships to be aware of. There has to be some maximum angle that a u-joint can work thru, and I understand this to be 3 degrees, with no more than 2 degrees being optimum. So, along with the engine angle and pinion angle, you need to check the driveshaft angle (is the pinion yoke above or below the transmission yoke). Lets say the engine is at 3 degrees down in back, and the pinion is 3 degrees up in front (all these angles for sake of discussion are relative to 0 degrees or horizontal), this gives the parallel angles, and if the driveshaft is at 0 degrees you should be ok. But, if the pinion is ABOVE the trans yoke (like in your one tone crew cab example) such that the driveshaft is 1 degree down in front that would mean the total angle the u-joint has to work thru is 4 degrees. So, I guess what I'm saying is that the absolute angle isn't relavent, but the relationship of the input shaft angle to the output shaft angle on a u-joint is critical and should be kept to a minimum. Thats why things like tire size play into it, or frame rake....etc. Is that correct Chicane?

    6. #6
      Join Date
      Sep 2006
      Location
      Chicago
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      355
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      thanks chicane

      I would just like to thank you chicane for taking the time to answer my question so thouroughly. give someone a fish and they will eat for a day, teach them to fish and they'll eat for a lifetime. much appreciated. you pointed out some stuff I'm embarassed for not realizing on my own.

    7. #7
      Join Date
      Dec 2002
      Location
      Lost Wages, Nevada
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      2,684
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      Quote Originally Posted by derekf
      ...would you suggest something along the lines of the -2/-3 degree drag setup, or less than that since we're not all about going in straight lines?
      Good question Derek. Honestly, I believe it would have more to do with the suspension type, spring rate... transmission type and whether or not its going to be driven on the street. For the record, the OEM housings are set to 4*.

      With a leafspring axle, the higher the spring rate... the more resistance it will have to an IC change (IC and pinion angle are inter related through this change). With a link type suspension, it has little to do with it as the links maintain the IC. But, with little to no IC change, the set absolute angle will stay within the maximum joint working angle. Lower spring rates however, will allow the spring to wrap up and this will not only change the IC but it will also change the pinion angle. Pinion angle is important to rear suspension efficiency, but don't expect to see huge gains in proformance based on a 1- or 2-degree change. The idea is to minimize driveline angle under acceleration to reduce power loss through the U-joints.

      Too little angle will cause vibrations in a street chassis tho.

      Now as for the transmission type... it has been my experience that you can get away with less angle when using a manual transmission with a lowered ride height. Not to mention that a torque converter eats up some torque and its not transfered to the rear suspension, so it isnt necessary to tighten up the absolute angle as much.

      On my 67, I have the angle set to -2.5*... because of the spring rate and the design of the spring itself. Not to mention the ride height itself. So... you bet. -2 to -3 is acceptable if the engine mounting and suspension is up to the task.

      Rubes... I think you got it right. Or, at least I agree with your example/explaination. Ill have to go back and look into the maximum working angle theory of mechanical joints (specifically the u-joint itslef) but I believe I heard that figure is somewhere around 4* total. Dont quote me on that just yet though...

      But like I said... too little angle will cause vibrations in a street chassis. I could never get a street chassis to work without vibration with any angle under -2.

      70... Your welcome. But dont sweat it man. Asking questions is how we all learn. Even if all it takes is a little jump start to get the brain thinking on its own again. Realization merit's understanding.

    8. #8
      Join Date
      Sep 2004
      Location
      Chicago - western burbs
      Posts
      673
      Thanx...I'm fighting a situation on my LS1 conversion into my 61 Impala right now reguarding this. This car has a two piece driveshaft, so I'm considering them as two independant systems, and dont beilieve the angles need to match in this case. As long as the max angle each u-loint sees is more than 2* (i also read about vibrations with too little angle, and meant to say that in my first post) but less than the max 3 or 4*. Does that sound like a reasoable assumption, or should they still match? My problem right now is that the front of the engine is as low as I can get it. and the trans is jammed up into the floor and still I am at 5.5 to 6*down at the trans. The driveshaft is parallel, so I seem to be exceeding the max u-joint angle. And with the trans touching the floor, I'm sure I would feel the slightest vibration. now I know others have done the LS swap on this chassis without cutting the crossmember to lower the front of the motor or cutting the tunnel, so either there are a few cars with seriouse vibration issues, or I'm missing something. I'm already marking my crossmember to cut it and lower the front of the engine to get a reasonable working angle rather than "see how this works" and fix it later. although 4* is closer to 6 than the 3 I originally thought.

    9. #9
      Join Date
      Dec 2006
      Location
      Lodi, Ca
      Posts
      81
      Here is what a few Guru's say:

      Pro-stock chassis builder Jerry Bickel: Negative angle down
      ladder bar suspension : 1/2 degree
      4 link: 1-2 1/2
      Leaf spring: up to 6-7
      Quote: a straight driveline delivers the most power to the rear wheels.

      Ray Currie:
      Street car: 2 degrees
      Quote: people increase the pinion angle to increase dragstrip bite, but he does'nt reccomend that for a street car.

      **** Miller:
      400 Hp: 2 degrees
      500-650HP: 3 1/2-4 1/2
      700+ HP: up to 7 degrees
      Quote: the greater the pinion angle, the more horsepower the driveline will consume.

      The just of it all is that you want the driveline, rear and trans as straight as possible under full power. Nose down degrees are to compensate for flex in the rear suspension and the nose raising under power.
      1973 TA G Machine
      2000 BMW 540 G Sedan

    10. #10
      Join Date
      Sep 2006
      Location
      Southern Indiana
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      Ok for the most part some stuff is "true",,,BUT.
      On a 2 piece driveline the rule of thumb (ie this is done to stop unwanted harmonics is to leave the front shaft to the carrier bearing level and centered.
      Now as for the pinion angle I tend to disagree because if you actually look inside a differential it requires some down angle relative to the drive shaft or you will starve the front pinion bearing.
      I did this in my truck after installing air ride, my axle brackets are not rotated up enough and my pinion was/is pointed up towards the bed of my truck.
      I am going to swap in a 4l60 or 4l80E into my truck in the future and I will rebuild the rea diff and install new brackets.
      Also if your pinion is pointed up it can and will cause a pinion nut to loosen as the motion of most cars(unless your setup goes pinion down upon acceleration) and you will wind up with even more up angle.
      Now if you set it at a neutral (straightline ) then under accelration it will go up and cause shaft whip, been there ,seen that on a semi.
      and trust me if pulling 80,000lbs around isnt at least similar to putting 500 to 600 ft lbs through a torque multiplication factor in converter/transmission into your drive line you want the drive line to come neutral (ie hard load straight front to rear).
      After having ate up several pinion bearings in cars because of jacked (messed) up pinion angles I speak professionally and from experience.
      also if it has no down angle and a slight side to side off set the pinion seal will leak.
      We fought this in a race/street car a friend bought, the DS was straight at rest and centered in the car too. 7 pinion seals later the axle locked up, we had another diff set up nd it has off set on both angles and it never leaked again.
      It wasnt the other diff as a friend bought it and had it retubed and I rebuilt it and it lives today dry as a bone.
      Heck I had an original GM tool oinstall the seal a couple of times.
      As for running more than 5 degrees down pinion angle will eat ujoints.
      If you get too much up angle under load because of power your rear suspension isnt going to plant it and you need an up grade or a pinion snubber.
      For a leaf car you can drive up to 4.5 down angle for tuning the "bite" on a leaf sprung car but recheck your pinion nut regualrly it can loosen.
      Red loctite is your friend and new pinion nuts.

      For others stick in the range of 1 1/2 to 2 1/2 down and tune as needed for "bite"
      I have had discussions with Currie guys on pinion angle for bite and then have people come aske me why thier car wont hit the track hard, we play pinion angle and get a great hook.
      Don t get me wrong it still has to do with the intersection point of the rear suspension and where the "lift" is pulling on the chassis.
      When I was racing back in 86 we had a 86 SS Aerocoupe with a 427/4 speed/12 bolt ladder bar car and generally had anywhere from 2 3/4 to 3 1/2 degrees down agle and could get it to hook so good I trashed Goodyear slicks, we went to Firestones and had no moretrouble and went 3 tenths faster too.
      The car was videoed and we were getting tire wrap like top fuelers (I like torque so the engine was built for it) we had several people just blown away why our setup ran good.
      We had the NHRA SS et record but never backed it up and then we were told we wouldnt even get credit for hitting the number first.
      Let along anything else but we knew we did the first one in our class.
      AND we trailered the actual "record holder" haha.
      Anyway choose your spec and run it if it makes problems yuo get to fix it.
      Also for the engine one of the reasons for engine tilt is to allow the engine oil to roll back naturally. I prefer to set my engines 3 degrees down (in the back) on the intake end rails of SBCs/BBCs .
      Had a car with engine down to the front and it whipped oil so bad it ate one set of rod bearings. Well in the front anyway. Releveled the engine and tada it neverdid it again.
      also the word I got for a race engine being down in the front on a race car is because the car settles with the front end UP at hard load.
      I set drag car engines at 3 deg down that launch hard with the front at full rise and the front tire just"skimming" the road.
      Most race engines have some much windage equipment that the down angle doesnt hurt a drag only car.
      Take this for what its worth.
      Lee