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Old 08-05-2008, 08:53 PM
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engine leveling

Hey guys, I placed my engine in my '39 Ford tudor to see about finishing the floorboard bracing. Then I decided that now might be a good time to go ahead and make the motor mounts. Question: it's sitting close to where it will be going down the road. I don't have any interior or glass, seats, or fuel tank in it. The motor is level now. How much margin do I have? What if a guy wants to change the stance of the car after it's done? How much can I do by changing the trans level? Thanks in advance, Rod

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Old 08-05-2008, 09:21 PM
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Quote:
Originally Posted by raj4851
Hey guys, I placed my engine in my '39 Ford tudor to see about finishing the floorboard bracing. Then I decided that now might be a good time to go ahead and make the motor mounts. Question: it's sitting close to where it will be going down the road. I don't have any interior or glass, seats, or fuel tank in it. The motor is level now. How much margin do I have? What if a guy wants to change the stance of the car after it's done? How much can I do by changing the trans level? Thanks in advance, Rod
Put the intake manifold on and level to the carb boss. Engines usually sag about 3 degrees when installed, the carb boss reflects this and is level when the tail of the engine and tranny drop the "right" amount.

If this is FI, the same rules apply; but the manifold isn't compensated since FI doesn't care if it's level and plumb. So you'll have to get a combination protractor and level to figure this out. This droopy angle stuff is intended to take some of the angle out of the u-joints between the end and aim of the tranny and the angle and aim of the rear axle's companion flange.

Certainly you can find yourself on your own in trying to set all this up and may need to do this differently than the typical Detroit solution.

Bogie
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Old 08-05-2008, 09:26 PM
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leveling the engine

I leveled the top of the carb, front to back and left 2 right.
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Old 08-09-2008, 11:14 PM
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Thanks guys

Hey guys, Thanks for the engine leveling tips. I'll proceed, Rod
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Old 08-10-2008, 09:06 AM
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I install them based on the driveline angles. I've disagreed on this before and got flamed, but I'll respectfully speak my opinion again.

Let's say for instance you are installing a different engine but leaving the rear axle alone. If you install the carb boss level, the chances that your driveline angles will work are slim to nil. The carb has a wide range of angles at which it will operate, but the driveline doesn't.

The true reason for the carb boss slanting forward is not so that it can remain level, its so the carb can operate properly under acceleration when fuel demands are the highest. If a carb is one or two degrees off, its perfectly fine. If a driveline angle is off by 1 or 2 degrees, its not.

The other reason I know this is from simple logic. If you measure most carb mounts, they vary from 4 degrees to as much as 10 degrees on more aggressive intakes that might be used for drag racing or heavy acceleration. If you put an engine in at 10 degrees down just to level the carb, you're nuts.

Intake manufacturers alter the angle of the carb boss to work in stock applications. You can take off your stock intake with about 2 degrees at the carb and replace it with an RPM air gap with about 6.5 degrees at the carb and it will work fine, but if you randomly altering the engine angle to relevel the carb, you'll find yourself building custom crossmembers, motor mounts, and completely re-engineer the driveline angles.

Having about 50 oddball engine swaps under my belt at the shop, I can safely say; put the engine in where it needs to go for the DRIVELINE, not the carb. Engineering an entire drivetrain around a carb angle is pretty pointless.
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Old 08-10-2008, 09:15 AM
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Old 08-10-2008, 09:31 PM
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re to curtis73

Hey curtis72, It sounds like you've done this sort of thing a time or two. I think yours is the answer I'm looking for. I had wondered about the drag racing, front end up angle also. I didn't know that the racing intakes had a different angle. Makes sense. Thanks for all the good info. I checked the angle of the output shaft the other night during my "experimentation" and it was not quite 90 degrees. I think another post mentioned being in line with the companion flange at the differential. Am I getting close? Please clue me in if I'm not. This is my first project of this proportion and I want to get it right, both for the street and maybe an occasional trip down the 1/8 mile. Thanks again, Rod
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Old 08-10-2008, 10:26 PM
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Yes Curtis has this exactly right.

The carb base hardly matters, the fuel in the carb will be sloshing around every time you brake, accelerate, or go around a bend in the road, or up/down any hill. If it is not exactly level it makes bugger all difference to anything.

But drive shaft angles are important for both wear and vibration. There are two ways of approaching this to get the angles right. Either "parallel geometry" or "broken back geometry". Either system is correct and both work.
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Old 08-11-2008, 01:03 AM
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I'll add one more factor:
An IRS like The Jaguar axle are made to be mounted at 90 degrees. Not 2-3 degrees off.
Mounting this axle 2-3 degrees off, will result in heavy binding when the rear wheels moves in bumps and turns.

So a car with a Jaguar IRS must have the motor leveled to get the setup right.
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Old 08-11-2008, 01:21 AM
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Not necessarily Staleg.

What you say is definitely correct, but there is also another way that is correct too.

While I agree a Jag rear end should be mounted level, with horizontal pinion angle, the engine and transmission can still be mounted with a downward slope.

The trick here is to adjust the height of the end of the transmission so that both uni joints work at the same angles with respect to the drive shaft. This is the classic "broken back" geometry, and it works fine.

For instance diff pinion horizontal (0 degrees)
Tailshaft sloping up towards gearbox 4 degrees
Engine and transmission sloping up 8 degrees

If you extend lines from both diff and gearbox they will cross exactly half way along the drive shaft. You can adjust gearbox mount height to achieve this, especially if the drive shaft is fairly short.
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Old 08-11-2008, 01:22 AM
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I guess no one thinks about the floor clearing the trans either?


I have found in the older cars that I've set up the mounts in, mostly model As through 40 fords, that a 3 or 4 degree angle angle works fine, if you set up the front of the motor so the centerline of the crankshaft is level with the top of the frame rails at the balancer, the motor slants down towards the rear at 4 degrees. this is with the frame at a 2 degree rake down in front. This usually works well if you are putting a MII also.

Setting the motor up that way makes it easy to make a trans tunnel, as the rear of most transmissions will clear the non removeable section of the floorpan. And on most intakes, at that angle, the carb sits level, which makes the air cleaner sit level...If the carb doesn't care, then why not make it look good while you do it. Also, it seems that the trans pan sits level with the ground when the crank centerline is at a 3 or 4 degree angle.


I always set up the rear end afterwards, to get the right pinion angle anyway.

I'm not saying anyone is wrong here, but that's how I do it.


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Old 08-11-2008, 01:31 AM
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Yes definitely, floor clearance usually makes it impossible to mount the engine level, it almost always has to slope down some.

There are two ways to set a correct pinion angle.

One is to set it parallel with the engine and trans, to give equal drive shaft angles in OPPOSITE directions.
The other is to make both angles the same but in THE SAME direction. Both are geometrically correct.

With a Jag IRS there is no option to horizontal mounting, so you are screwed trying to tilt the pinion upwards. But there is an alternative, if the engine and trans absolutely cannot also be mounted horizontal.
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