I know this has been hashed to death, I have ready many posts on the subject as well as online info, but I want to clarify something because I dont want to have issues later. This is for my 47 cadillac which will be a street car with leaf springs, no racing, so I do not think I have to worry about pinion climb issues.<p> I normally set my frame level, set the trans at 3 degrees down, pinion at 3 degrees up, build my engine / trans mounts and am done. Because of the accessory drive system on the engine I am using I cannot get 3 degrees, everything fits nice with the engine 5 degrees down. I do not know yet if I have enough room to shim up the trans to go to 3 degrees but I do not think I do because of clearance in the X frame. So I plan on putting the pinion gear 5 degrees up to match the engine.<p> I have read that ujoints want 3 1/2 degrees max angle, question is that the angle of the engine tilt / pinion angle or is it the working angle? Is the 5 degrees NG or is really ok if my working angle is 0 degrees? (5 degree engine angle +2 degree driveshaft angle = 7 degrees, minus the 5 degree pinion angle +2 degree driveshaft angle = 7 degrees, subtracting them gets 0 degrees). I have seen some pretty steep engine angles in drag cars but what about for the street? 5 degrees is not all that steep but not the 3 degrees I normally can get.
http://www.carcraft.com/howto/91758/index.html Someone in this article states up to 7 degrees with leaf springs, I guess the biggest thing is a staight line from the crankshaft to the pinion.
One issue is to have the phases correct so that the angular velocities are constant, w/rpm leaving the tailshaft and arriving at the pinion. If the angles cancel and are at least 3*, then the lube 'motion' will be sufficient to serve the needle bearings. Another degree or two? I'd like to hear some war stories on this. (I suspect post #4 refers to post#2)
Thanks, I will make sure to have the joints in phase when I make the driveshaft. The car craft info is good but it is for spring wrap in a drag car, other than normal suspension cycles and an occasional burnout this car should not see that kind of spring wrap.
You bring up a very important point, and one very often ignored or mis-understood. The maximum working angle for a single cardan U-joint is 3 degrees, which equates to about 5500 maximum drive shaft RPM. So, with the vehicle at ride height, the engine/tranny angle should be within 1 degree of the pinion angle, along with working angles under 3 degrees. The actual engine angle really depends on the intake (carb angle), vehicle rake, personal preference, etc.
Yes, with the suspension at ride height. Leaf springs get longer as the suspension get compressed, and my pinion angle goes from 3 degrees up with the rear of the car with no load (think of the car on a lift and the rear end hanging free with the wheels off the ground) and then to 5 degrees up when compressed to ride height. I used ratchet straps to compress the rear suspension to drive height during initial mock up, set the pinion to 5 degrees up with the rear centered, and tacked the spring pads to the housing. This car is not a drag car so I set everything up as it would be during normal driving conditions.
Key is to install engine with carb mounting surface LEVEL in both directions then measure the degree of the trans output shaft and match it with the pinion angle. You need the carb level so floats work properly. you can also check the angle at the pad where the starter mounts.
Yes, and 5º is totally fine. If you are using very soft leaf springs, you can put the pinion at 4º. In most cases, this is not necessary.
He's showing a picture of what appears to be a GM poly tank, most often used to fuel an LT or LS engine. This one looks like a Camaro unit, so no carburetor, more likely EFI. +/- 1º-2º on a carburetor base is not going to make or break a setup. There are few truly level roads.
Good eye on the FI tank, it is from a 95 caprice wagon. Has a side fill that will work great with the 47 cad original gas tank filler tube and fits great after losing the spare tire well in the trunk. Engine will be fuel injected LT1 with a 4L60E so no worries about carb level.
The 3 1/2 degrees max U-joint angle mentioned is the difference in degrees from the driveshaft to tailshaft or pinion centerline.
+,- 1,2 degrees will work at carb base but shooting for zero is what your after. seeing this is F.I. it really doesn't matter since fuel system is closed loop not venturi based. centering engine/trans isn't critical either, manufactures have been offsetting power plants to clear steering boxes for years.
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