The Stovebolt Site Forums The Shop Area Engine Shop 250 engine mounting angle

I'm getting ready to put motor mounts in my 57 3100 to support the 250. I noticed the stock 250 intake is tilted. If mounted so that the carb is level, it looks like the engine will be about 5 degrees nose up. Is this normal? Or do I have some kind of special application intake?

regards,
Leon

Carb level is just a average location, as the roads and terrain change, so does the carb angle. Adding cargo also changes the angle.

The main reason for the slant is to get u-joint angles, read up on drivelines if you are not sure what you need. Ideally you want 3 degrees operating angle at each end, no more then 5 degrees, and not straight or zero angle. All measurements taken from driveline to tail shaft, and driveline to pinion. Frame angle or road surface has no bearing on u-joint angle. Once you figure these out, the engine intake angle will fall into place. You also need full weight on the chassis to determine where the rear axle is going to set. Use ratchet straps to pull the springs down or add weight to equal the ready to drive weight. You kinda have to work from the rear forward if the axle has original mounts.

Joe

I measured the angle on my 250 and it has 3 degrees difference between the engine and manifold angles. So I'm setting up the mounts to make the engine 3 degrees nose high. But I'll check the pinion angle like Joe suggests. If its not close to 3 degrees I'll rethink the engine angle to make it similar.

regards,
Leon

Its a lot easier to check now then once its together. Carbs will run a slant so don't worry if it doesn't come out just right. The driveline is more important. As long as both ends have approx. the same angle, they will cancel each other out and run smooth, doesn't matter if pinion is pointed up or down.

I removed 1/4" spacers from under my motor mounts trying to get clearance at the radiator and didn't notice any difference in ride or vibrations, so its not real critical to be right on the money. Maybe I should measure the angles now to see how far I moved it!
Joe

I finished putting in the mounts (except for welding the flanges to the cradles). The unloaded pinion angle is 5.5 degrees. I figure it'll drop to about 5 when loaded. The engine ended up at 4.3 degrees. I plan to run a slight rake on the truck, so the carb angle should end up within a degree of level. I feel pretty good about how this has worked out. The saga, with pictures, is on my website
for your amusement.

regards,
Leon

It looks pretty good! Did you run a straight edge from trans to pinion to verify the u-joint angles? Sounds like your numbers are right, but if the trans sets high or the pinion is low, the actual u-joint angle could be off. Just remember, the working angles have nothing to do with the frame or driveway angle, is all about from pinion to driveshaft, and driveshaft to tail shaft. Your meter is just reading from a level surface which has nothing to do with working angles of a u-joint.

I bet you are close though, and well on your way.

Joe

No, I didn't try to estimate the working angle yet. I know you need some offset in order to roll the u-joint bearings a little and distribute the grease or they'll wear out quickly. I was just concerned with making sure the pinon and trans angles were close enough to prevent vibration problems. Part of that is that I couldn't think of an easy way to measure working angle. Using a length of angle iron as a straightedge didn't occur to me. Also it just dawned on me that I can measure height off the floor for each end and calculate the driveshaft angle. Thanks for the spark. I'll try to check it today.

regards,
Leon

When I set mine up, I set the two yokes to the same hight off the ground by using four jack stands under the axles. Once both yokes were on the same level, I new the driveshaft would be level, then it was just a matter of measuring the pinion and trans angle to calculate the working angles.

Joe