Engine & transmission angle?
 

Hi all,

I am trying to get to the bottom of what angle the engine & transmission should be positioned at in my '66 GTO and I haven't been able to get a fully complete answer elsewhere.

First a little bit of background... I boxed in my frame, and as a result it became necessary to fabricate "shelves" for the transmission crossmember to sit on top of since it can no longer go inside the frame rails. I'm sure that I'm close to where I need to be, but I just want to confirm the correct angle of the engine & transmission before I proceed with setting my rear end pinion angle and then measuring for a driveshaft.

So, if I jack the car up and level the frame to zero degrees, what should the pitch of the engine & trans be? Somewhere around 3-degrees? A key factor here is that I want to know what the angle of the engine & trans should be relative to the frame, not relative to the ground. If the car is resting on its wheels & tires, the measurement will be affected by the springs & suspension.

Crankshaft /Trans main shaft/ Yoke is on one angle

The pinion is on a second angle. The U-Joints angle parallels the engine trans drive shaft angle. Yoke and Pinion might be on 4 degree angles and driveshaft tube on a 7 degree angle.

https://www.drivelinesnw.com/part-tr...ngle-problems/

Tom V.

I would say whatever gets the carb pad level. That is usually in the 3 to 4 degree range.

Yes I think you are correct with the 3 degrees….this is what I recall that I measured with the frame level.

Aren’t most intake manifolds carb flanges at a 3 degree angle so the carb is level relative to the engine? Maybe you can also check that.

But Tom is right, what is important in the end is the relative angles between trans-driveshaft-reared pinion for proper operation.

I think I understand the relationship between the yoke, drive shaft, and pinion, but what I'm trying to find out is the factory slope of the engine & trans when the frame is completely level at 0-degrees. From what you're saying, it sounds like if I level out the frame, the engine & trans should be roughly at a 4-degree downward slope. That's all I need to know right now, as I don't have a drive shaft yet. I have adjustable rear upper control arms, so it will be easy to set my pinion angle. Just want to make sure my engine & trans are generally in the ballpark of where they should be before proceeding to the next steps.

i have my engine hanging from a I'beam / hoist in the pole barn under a tilt device also have a starret bubble protractor i can derive the difference in angles between the carb surface and valve cover head surface if you need it

in fact earlier this morning i leveled the engine with a bubble on the carb surface
only caveat would be its a tomahawk intake

When I set them up from scratch I shoot for 1-3 degrees down. I never go more than 3, haven't found a need to.

This sounds like a fairly modified car. So the factory specifications won't mean much. It is much more important to think of the whole drive train as a complete system.

If you have lowered the car the pinion angle changes, change the drive shaft length the angle of the drive shaft changes. All of these angles must work together for a smooth operating power train.

The closer you can get the car to it's finished ride height before setting the engine angle will save you work down the road.

I suggest mocking the engine and transmission in the chassis (at ride height), then using string from the output yoke to the rear end. This will allow you to check that the angles are are in the ballpark.

Here is a link to another site that may help you with your design.

https://www.pro-touring.com/threads/...e+shaft+angles

The Spicer website has some good information on the subject.

https://spicerparts.com/calculators/...gle-calculator

I hope this helps you. Feel free to post any questions.

Thanks, guys. I measured things last night and the engine & trans are in fact at a 3-degree downward slope relative to the frame, so by the sound of it that should be fine. I'll adjust the pinion angle of the rear end to where it needs to be once the car is closer to full weight. Just wanted to make sure the engine & trans was positioned correctly in case I needed to shim it, but all is well.

i checked my engine assy put the stick flywheel at 90° to earth then checked carb flange came up with 5° difference, but as noted before i have a tomahawk intake from China, might be different from a OEM intake

Some intakes naturally rake the carb forward, even some OEM stuff, by design. So it's really not part of the equation.

On some of these intakes you'd have the trans pointing at the ground pretty severely to try and get the intake level, and if you play with an angle finder on the output of the trans, you'll know what I mean. You have to move the trans at least an inch just to get a degree out of the angle finder.

ive never seen a OE intake without a carb slant
just offering a data point OP can use it or not

Trans Mount is in a different spot on a Doug Nash 5 speed trans vs a Muncie 4 speed.

I had to drop the trans mount deeper into the trans cross-member to get the correct angles again. So we cut out the "pocket" where the muncie mount would be and dropped the floor to get the correct angles for the trans and the 9" Ford Rear Axle Pinion.

Perfect now.

Tom V.