gurneyhm
Apr 29th, 03, 06:36 PM
OK, thanks in advance for any thoughts. I'm building a 383, and I've been doing some reading. I am considering skiping the align honing process. Let me know your thoughts. This is what I read in one of David Vizards book...
"An operation that your machine shop may suggest is align honing the main bearings. My comment here is "forget it". Its an expense that returns little if anything in the majority of cases. Align honing subsequently can be done in the unlikely event the crank does not turn freely during assembly. A lot of engine builders will argue the point that friction must be reduced to a minimum.
My sentiments exactly, but align honing probably won't do this. Here is the logic behind this statement. a small block Chevy making 700HP can twist from corner to corner as much as 1/16 of an inch. Therefore, under running conditions, the bearings aren't in line. Even if we were to have them exactly in line its unlikely that the engine would make significantly more horsepower. Why? Because the crank is riding in a bed of oil. The crankshaft is bending. Its able to absorb this bending. No matter how much force there may be, the potential loss in torque that occurs is due to the force times the radius at which the friction is acting. If the coefficient of friction is zero, then, no matter how large the bending forces involved, there would be zero torque loss because any number multiplied by zero is zero.
We don't have zero friction at the bearings, but its low. The oil film between the crank and its bearings is stiff. Even if the bearings are out of line by a considerable amount, there will be no measurable difference in the power seen at the flywheel. Testing with deliberately distorted blocks and cranks supports this theory. The bottom line is, skip the align honing".
Thoughts?
"An operation that your machine shop may suggest is align honing the main bearings. My comment here is "forget it". Its an expense that returns little if anything in the majority of cases. Align honing subsequently can be done in the unlikely event the crank does not turn freely during assembly. A lot of engine builders will argue the point that friction must be reduced to a minimum.
My sentiments exactly, but align honing probably won't do this. Here is the logic behind this statement. a small block Chevy making 700HP can twist from corner to corner as much as 1/16 of an inch. Therefore, under running conditions, the bearings aren't in line. Even if we were to have them exactly in line its unlikely that the engine would make significantly more horsepower. Why? Because the crank is riding in a bed of oil. The crankshaft is bending. Its able to absorb this bending. No matter how much force there may be, the potential loss in torque that occurs is due to the force times the radius at which the friction is acting. If the coefficient of friction is zero, then, no matter how large the bending forces involved, there would be zero torque loss because any number multiplied by zero is zero.
We don't have zero friction at the bearings, but its low. The oil film between the crank and its bearings is stiff. Even if the bearings are out of line by a considerable amount, there will be no measurable difference in the power seen at the flywheel. Testing with deliberately distorted blocks and cranks supports this theory. The bottom line is, skip the align honing".
Thoughts?