motor home big block

[Jim100]

Is there any chance that a early 70's big block from a motorhome (not sure of cubic inches yet) will have crank that is drilled for manual transmission?

[PwrWgnDrvr]

Unlikely, but its easy to drill, even by hand.

[Wildergarten]

Is there any chance that a early 70's big block from a motorhome (not sure of cubic inches yet) will have crank that is drilled for manual transmission?

If your intent is to rebuild that motor, the crank grinding shop can probably bore it for you.

[Jim100]

I'm not sure what condition it's in but one of the coworker/friend deals that cant be passed on. My truck has a fine running crate 360 so hard to justify a swap. Maybe a shop project.
Interesting that it can be drilled by hand. Stand the thing on end and take your time? It would be for a NP-435. (23 spline mechanical from a 1970)
Thanks guys.
jim

[dodgeboykim]

I drilled a 400 cast crank. Bolted a flywheel on with engine sitting flywheel up and used a magnetic drill to drill crank hole for bushing.

[PwrWgnDrvr]

Its a 1" dia hole, so I used a variable speed right angle drill. Hard on the wrists to drill that size hole with a regular pistol grip drill without a side handle.

[martincom]

Just a note in regards to the crankshaft. At some point in the early '70s the non-HP 440s utilized a cast crankshaft rather than a forged. So a motor home 440 of the early '70s and later would have a cast iron crankshaft. Not ideal for high performance applications, but should be more than adequate for a truck application.

While I'm not 100% certain, that cast iron crankshaft may also be externally balanced. I can't remember if the external balancing was small blocks, big blocks or both. I'm sure there are online resources that expound on this and will offer info on how to determine if the 440 you're looking at has a cast iron crankshaft.

If it does, that could present issues for you, as the balancing was done by the amount of weights and position on the torque converter. I'm not sure just how you would transcribe that to the drilling of a manual flywheel.

[Jim100]

Its sounding like this engine is a 413. Lots of potential issues from what I hear.

[712edf]

Just a note in regards to the crankshaft. At some point in the early '70s the non-HP 440s utilized a cast crankshaft rather than a forged. So a motor home 440 of the early '70s and later would have a cast iron crankshaft. Not ideal for high performance applications, but should be more than adequate for a truck application.

While I'm not 100% certain, that cast iron crankshaft may also be externally balanced. I can't remember if the external balancing was small blocks, big blocks or both. I'm sure there are online resources that expound on this and will offer info on how to determine if the 440 you're looking at has a cast iron crankshaft.

If it does, that could present issues for you, as the balancing was done by the amount of weights and position on the torque converter. I'm not sure just how you would transcribe that to the drilling of a manual flywheel.

Yes they switched to external balancing when going to the cast crank. 360 small blocks were external balanced, & cast crank 400/440 big blocks.
Easiest way to tell is looking at the harmonic balancer. Internal balanced have about a 1" think dampener. External balanced will be considerably thicker.

Bucky

[PwrWgnDrvr]

Just a note in regards to the crankshaft. At some point in the early '70s the non-HP 440s utilized a cast crankshaft rather than a forged. So a motor home 440 of the early '70s and later would have a cast iron crankshaft. Not ideal for high performance applications, but should be more than adequate for a truck application.

While I'm not 100% certain, that cast iron crankshaft may also be externally balanced. I can't remember if the external balancing was small blocks, big blocks or both. I'm sure there are online resources that expound on this and will offer info on how to determine if the 440 you're looking at has a cast iron crankshaft.

If it does, that could present issues for you, as the balancing was done by the amount of weights and position on the torque converter. I'm not sure just how you would transcribe that to the drilling of a manual flywheel.

Yes they switched to external balancing when going to the cast crank. 360 small blocks were external balanced, & cast crank 400/440 big blocks.
Easiest way to tell is looking at the harmonic balancer. Internal balanced have about a 1" think dampener. External balanced will be considerably thicker.

Bucky

Bucky, that is good to know. Now here's a different question that applies to this situation.
30 yrs ago I bought a 1973 motor home 440 (auto trans). It has the cast crank with fat damper. I did not buy the trans or torque converter. At the time, I didn't know about the external balancing. But, at the time, along with the 440, I also bought a new in the box forged crank. All of that stuff is still sitting in my shop. The question is, if/when I install the forged crank, will it still be external balanced and if so, how do I deal with that?

[martincom]

The forged crankshafts were internally balanced. You'll likely see some partial drillings in the crank arms.

While I can't remember with certainty, I believe the cast iron crankshafts had some stampings on them to indicate what weights were required and where.

[712edf]

I believe that its not just the crank, but rods & pistons come into play. Or at least those are addressed by machine shops when doing a balance/blueprint. The rods/pistons are weighed & everything is lightened to match the lightest one. Convertors/flywheels & the dampener are matched to a particular type of crank. Swapping parts may cause problems unless the entire assembly is balanced.

In my youth I purchased a 440 short block which had an externally balanced cast crank. I didn't know about such matters & used my balancer & TC which were for forged crank. Motor ran wicked but vibrated all to hell in a certain RPM range. Wound up breaking 3 tailshaft housings. I finally ditched the motor altogether.

I wont hardly touch a 360 as far as swapping them into something, they are bastard motors in my opinion.

Bucky

[PwrWgnDrvr]

Tnx for that insight. I've had motors balanced in the past so I'm familiar with that. Seems I can take the forged crank and all the parts to a shop and it won't be complicated to get it right.