Has anyone ever................

[barbee6043]

too bad the "muscle car" died as Ma Mopar began to replace the 340 with the 360. I read an article where Larry Sheppard mentions some interested things that would have made the 360 revered as the 340.

 

[JBurch]

It would come down to "difference in friction". There's an "App" for that, well...not an app but a formula!!

The engineering of a bearing’s Babbitt lining is usually completed during the design of the machine. In selecting the proper type of Babbitt for a particular job there are a number of factors to take into consideration, the most important of which are as follows:
1.Surface speed of the shaft
2.Load that the bearing is required to carry

There is no doubt that if a bearing is to be highly loaded in relation to its size, a high tin alloy is desirable; whereas for much slower speed work and less heavily loaded bearings, a lead-Based Babbitt may be employed, and is far more economical.

1. Surface speed of the shaft: (The number of feet traveled per minute by the shaft circumferentially.)

Formula: (Pi x D x RPM) / 12 = S
Example: Determine the surface of a 2 inch diameter shaft going 1,400 revolutions per minute (RPM)
(Pi x D x RPM) / 12 = (3.1416 x 2 x 1,400) / 12 = 733.04 Ft/min

Where: Pi = 3.1416, D = Diameter of shaft, S = Surface speed of the shaft

2. Load bearing is required to carry: (the weight which is being exerted through the combined weights of the shaft and any other direct weights on the shaft and measured in pounds per square inch.)

Formula: W / (I.D x L.O.B.) = L
Example: Determine the load on a bearing of a 2 inch I.D bearing, 5 inches long and carrying a weight of 3,100 lbs
W / (I.D x L.O.B.) = 3,100 / (2 x 5) = 310 Lbs/sq.in

Where: W = Total weight carried by bearing, I.D = Inside diameter of bearing, L.O.B = Length of Bearing, L = Load bearing required to carry

You can actually calculate the amount of friction gained or lost simply by knowing the speed of the shaft, weight carried by the bearing,ID of the bearing, etc, etc.

I doubt you could measure it on a Dyno because threre are too many variables, it's like building two engines exactly alike, and I mean exactly!! The chances of them both having exactly the same horsepower is next to none, even though they were built the same!!

Treblig

Formulas, you must be an engineer.

My idea of how to conduct the test would be like this: a 340 block and a 360 block, they can be built to identical displacements at several points, pick one, build a block with a rotating assembly; every thing else is shared, heads, intake, carb, distributor, cam, lifters, oil pump. Run them, see what shows up.

Actually run them in 3 configurations, basic rebuild, street/strip, max effort 2hp per cubic inch, I think some where in there, there would be a cross over where the increased drag would show itself. How much and where, God only knows and he ain't sayin'.

 

[JBurch]

Its mostly brought up in my opinion because it falls into the old wifes tells category. And another thing to consider, is that a "narrow" rear main bearing can be installed in the 360, reducing a SMALL amount of bearing surface area. Its in the engine bible. ALSO, where the 360 has larger main journals, it has a SHORTER and LIGHTER piston than the 340, so that probally nullifies ANY bearing friction difference anyway.

I think you are on to some thing when you say "wives tails"

Shorter, lighter piston goes to Krazycudas comment about bearing load.

 

[Breadburner]

Just spin them with the cranks in a torqued down....I bet the one with larger journals has less resistance but not by much.....And definitely not enough to noticed on the dyno....

 

[273]

too bad the "muscle car" died as Ma Mopar began to replace the 340 with the 360. I read an article where Larry Sheppard mentions some interested things that would have made the 360 revered as the 340.

Too bad when the 71 340 and 360 were introduced they didn't drop a forged 3.51 stroke crank intro a 340 block and dropped the 340. I wonder what the debate would be then?

 

[jos51700]

If this is really keeping you up at night, the solution is simple. Bolt the appropriate cranks into the appropriate blocks, bolt a belt adapter to the crank flanges and an encoder wheel to the crank snout, and power the cranks with a supply of lube by an electric motor; no rods, no pistons, no cam drive.

Pick an RPM to run them at and see how much current it takes to spin each at the given RPM. The difference in current can then be easily converted to the hp gain/loss for a given crank.

As I said, too many variables to measure in an applied example, but the difference in drag: quite simple.

If you have these kinds of questions, get a Shigley's and start going to college. You'll do well in life.

 

[JBurch]

If this is really keeping you up at night, the solution is simple. Bolt the appropriate cranks into the appropriate blocks, bolt a belt adapter to the crank flanges and an encoder wheel to the crank snout, and power the cranks with a supply of lube by an electric motor; no rods, no pistons, no cam drive.

Pick an RPM to run them at and see how much current it takes to spin each at the given RPM. The difference in current can then be easily converted to the hp gain/loss for a given crank.

As I said, too many variables to measure in an applied example, but the difference in drag: quite simple.

If you have these kinds of questions, get a Shigley's and start going to college. You'll do well in life.

It doesn't keep me up at night............