Magnum serpentine belt on a LA?

[68383GTS]

Will a serpentine belt system off a 1999 Magnum engine bolt up to my 1974 318 LA?

 

[memike]

I would like to throw my hat in on this question also if you don't mind my friend.

 

[66fs]

I would think so, but you would have to swap everything from the front cover and damper/pulley. Then watch for any balance difference from the damper.

 

[justinp61]

Will a serpentine belt system off a 1999 Magnum engine bolt up to my 1974 318 LA?

Several years ago I read somewhere that the magnum's water pump turned in the opposite direction a LA does. I don't know if it does or not but it would be something to check before you bought any parts.

 

[68383GTS]

Several years ago I read somewhere that the magnum's water pump turned in the opposite direction a LA does. I don't know if it does or not but it would be something to check before you bought any parts.

Yes I would have to change the water pump.

 

[Professor Fate]

Short answer: No.
Long answer: Anything's possible.
As mentioned above, the entire timing cover/water pump assembly needs to be swapped from the Magnum- It has specific mounting points for the serpentine brackets. This will bring up bypass hose alignment issues with the 318 manifold, and you lose the ability to run a mechanical fuel pump. I'm not even sure the Magnum timing cover has enough clearance to run the long-nose LA cam; I never tried it. Use an early Magnum (bolt-on type) crank pulley on your 318 balancer. Your 318 also has a centered thermostat housing on the intake manifold which will interfere with the bracket; you will need to remove sections of the bracket, or switch to a late '70s (not sure of the exact year of the change) type manifold with the smaller, offset thermostat. This may not be an issue if you're not running AC, the offending section of the bracket can then be removed. There may still be issues with clearance to the LA heater hose nipple location. I don't believe all the mounting bosses are all there on the LA for mounting the belt tensioner and PS pump.
Can it be done? Sure. Is it worth the time/effort/frustration? It's not a bolt on. Better off getting one of the aftermarket serpentine setups if that's all you're after.

 

[Professor Fate]

Short answer: No.
Long answer: Anything's possible.
As mentioned above, the entire timing cover/water pump assembly needs to be swapped from the Magnum- It has specific mounting points for the serpentine brackets. This will bring up bypass hose alignment issues with the 318 manifold, and you lose the ability to run a mechanical fuel pump. I'm not even sure the Magnum timing cover has enough clearance to run the long-nose LA cam; I never tried it. Use an early Magnum (bolt-on type) crank pulley on your 318 balancer. Your 318 also has a centered thermostat housing on the intake manifold which will interfere with the bracket; you will need to remove sections of the bracket, or switch to a late '70s (not sure of the exact year of the change) type manifold with the smaller, offset thermostat. This may not be an issue if you're not running AC, the offending section of the bracket can then be removed. There may still be issues with clearance to the LA heater hose nipple location. I don't believe all the mounting bosses are all there on the LA for mounting the belt tensioner and PS pump.
Can it be done? Sure. Is it worth the time/effort/frustration? It's not a bolt on. Better off getting one of the aftermarket serpentine setups if that's all you're after.

Or better yet, just swap in the whole Magnum motor. Might be just as easy!

 

[DionR]

This will bring up bypass hose alignment issues with the 318 manifold

I am running a Magnum specific intake on my LA block with an LA timing cover and the bypass works fine. So I would guess going the other way should work ok.

The issue of the thermostat housing interfering with the bracket might make it mute though,

I'm not even sure the Magnum timing cover has enough clearance to run the long-nose LA cam; I never tried it.

Not certain, but it sticks in my head that there is enough room to run the eccentric on a Magnum TC cover even though you can't run the fuel pump. Even more certain you can run the long nose cam with a cut down eccentric for a spacer if need be. But take it with a grain of salt as it seems like something I read and certainly wasn't something I tried.

 

[DionR]

Not certain, but it sticks in my head that there is enough room to run the eccentric on a Magnum TC cover even though you can't run the fuel pump....But take it with a grain of salt as it seems like something I read and certainly wasn't something I tried.

I happen to have both an LA motor with a cam/timing chain/eccentric and a Magnum TC cover so I took some measurements and bolted things up loosely.

The end of the eccentric measured about 1.875" from the block. The Magnum TC cover measured about 2.0625" from the flat on the inside. And when I set the Magnum TC on the LA block, there was no interference. I should have measured the LA TC cover just to compare but didn't think about it until just now.

So, pretty confident you can run a long snout LA cam under a Magnum cover.

Hope that helps.

 

[MOPAROFFICIAL]

I happen to have both an LA motor with a cam/timing chain/eccentric and a Magnum TC cover so I took some measurements and bolted things up loosely.

The end of the eccentric measured about 1.875" from the block. The Magnum TC cover measured about 2.0625" from the flat on the inside. And when I set the Magnum TC on the LA block, there was no interference. I should have measured the LA TC cover just to compare but didn't think about it until just now.

So, pretty confident you can run a long snout LA cam under a Magnum cover.

Hope that helps.

Yep.
Magnum type Intake, front cover and water pump with pulley, accessory bracket, idler,tensioner , could use the coil setup if you're there since that bracket intermingles in there behind the tensioner...alternator setup.. 'probably a fuse upgrade required for 100+ amp version'... belt for no a/c no p/s or with p/s and use the mag pump... then I would look for a bolt on serp pulley for the existing balancer...
Otherwise pull yours and take it and have it checked on a balancer and match a magnum style to that imbalance
The eccentric fits on a long snout that also fits. Cut off portion that caries the ac. The dipstick might be a good swap since the mag bolts to the bracket and the old you may not get to easily after the swap.

 

[DionR]

Cut off portion that caries the ac.

Just be aware that the idler is in a different location between a bracket with AC and one without. This is really only important in that the belt will not fit when run with PS as it rubs on the WP pulley.

 

[MOPAROFFICIAL]

Just be aware that the idler is in a different location between a bracket with AC and one without. This is really only important in that the belt will not fit when run with PS as it rubs on the WP pulley.

In case I'm not getting you right.. I have 2 belts, one for ac and one that by passes under it.

 

[DionR]

In case I'm not getting you right.. I have 2 belts, one for ac and one that by passes under it.

Guessing I'm not saying it right. And not really following what you are saying.

Here is an example of what happens when an AC bracket is used without an AC pump but with a PS pump:

Now this may only be with the van PS bracket, I guess it puts the pump lower than the truck or jeep setup. Not really sure.

Here is the thread that came from - Van power steering bracket issues

 

[MOPAROFFICIAL]

Guessing I'm not saying it right. And not really following what you are saying.

Here is an example of what happens when an AC bracket is used without an AC pump but with a PS pump:

View attachment 1715802211

Now this may only be with the van PS bracket, I guess it puts the pump lower than the truck or jeep setup. Not really sure.

Here is the thread that came from - Van power steering bracket issues

That's what I thought you were saying. Van issue because of the power steering being lower than truck. I'd use truck stuff. You only need a shorter belt. Like 97 inches.

 

[DionR]

That's what I thought you were saying. So let me be clearer you use a different belt.

View attachment 1715802217

Gotcha. I've seen a different routing when there is no AC and no PS, but no idea what routing would work with no AC but with PS.

To be clear, it does appear that the higher PS mount from a truck or Jeep does seem to avoid the issue. I didn't realize that until I re-read the linked thread. So technically, the issue only comes up when running the van PS bracket.

 

[MoparLeo]

In other words get the complete front caver setup including accessories like the alt, p/s pump, a/c if you run one as you will need all brackets, pulleys, bolts, etc...
I recently purchased the complete front setup from a member for under $100.