Crankshafts

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OLFOOL

OLFOOL

OLFOOL
Joined
Jul 27, 2021
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New South Wales, Australia
Can I fit a 360 magnum crank into a 360LA block, I have looked around for info but have seen that pistons and rods in a magnum are lighter but thinking this could be overcome when balancing the parts? Basically use all LA internals but magnum crank. Any help appreciated here in Australia, :)
 
Pretty sure it will.
I know a 318 one will, same pn since the 60s in that case.
Look up a crank kit for a late LA and an early Magnum.
 
If you are already planning to balance the assembly, yes you can interchange the crankshafts. The Magnum crankshaft takes the same bearings, timing chains, and harmonic balancers but the one advantage is the rear main seal area on the crankshaft is ground smooth to take the modern two-piece seals with less leakage. All LA and aftermarket crankshafts for LA engines I have seen still have the grooves cut in for the old rope seals, which nobody uses in LA or Magnum builds.

Connecting rods on Magnums are narrower on the small end than an LA rod and the pistons are narrower too, but if you run a Magnum piston in and LA you just have to run the Magnum rods, aftermarket rods that are narrow enough, or grind the small end of the LA rods to narrow them before balancing the assembly.

With that info, you can use whatever parts you want in either style engine by just making sure the compression height of the piston is correct for the block you are running, and make sure the rod is narrow enough on the small end for whatever piston you are running.
 
OLFOOL said:
Can I fit a 360 magnum crank into a 360LA block, I have looked around for info but have seen that pistons and rods in a magnum are lighter but thinking this could be overcome when balancing the parts? Basically use all LA internals but magnum crank. Any help appreciated here in Australia, :)
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Depending on the weight difference, putting OEM LA parts on a Magnum crank may require Mallory metal (expensive) if enough material can't be taken off of the LA pistons & rods. Aftermarket pistons & rods tend to be lighter & stronger for either application.

Does the LA crank need to be replaced?
 
The LA and magnum 360 crank counter weights are the same. The external weights are different. IE damper and flywheel.
 
Locomotion said:
Depending on the weight difference, putting OEM LA parts on a Magnum crank may require Mallory metal (expensive) if enough material can't be taken off of the LA pistons & rods. Aftermarket pistons & rods tend to be lighter & stronger for either application.

Does the LA crank need to be replaced?
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Yes, 360 LA cranks are getting hard to find, have a bloke that has a magnum crank hence my question.
 
mod5v said:
The LA and magnum 360 crank counter weights are the same. The external weights are different. IE damper and flywheel.
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So if I get the magnum crank I will need a magnum balancer, I am using a steel flywheel for a 4 speed set up, I would like to think that it should all come together with a full rotating balance.
 
OLFOOL said:
Doesn't look like anyone has actually done it here.....
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Mopar did it. They were selling Magnum shortblocks with Magnum crank, Magnum rods, and Sealed Power pistons balanced to 360 LA specs. That was specifically so guys could replace LA 360 shortblocks with no hassle. They were based on early Magnum blocks that had LA oiling as well. And no heavy Mallory metal was needed to balance them for this purpose.
 
So I guess I need to fill in the blanks. 360 Cranks are same... so if you want to use factory balance.. the rest of the rotating assy needs to be magnum or LA . in other words if you want LA balance use LA pistons/rods/damper/flywheel, if you want magnum balance use magnum pistons/rods/damper/flywheel... if you mix and match have your machine shop balance the rotating assy they will need all the above parts.
 
mod5v said:
So I guess I need to fill in the blanks. 360 Cranks are same... so if you want to use factory balance.. the rest of the rotating assy needs to be magnum or LA . in other words if you want LA balance use LA pistons/rods/damper/flywheel, if you want magnum balance use magnum pistons/rods/damper/flywheel... if you mix and match have your machine shop balance the rotating assy they will need all the above parts.
Click to expand...
Hoping to use magnum crank with my LA pistons rods balancer etc
 
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