LA/Magnum Hybrid Questions

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sharpie

workin' stiff
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Hey all, I am getting into the final stages of my LA/Magnum project. Still a lot of $$ to go, but I feel like it's coming together (or will be once I get those heads). However, I still have some questions:

1. Flex-plate: What am I looking for?

2. Vibration Dampner: which kind? Thin/Thick? Magnum/LA style?

3. Bellhousing: Will an LA/904 housing work for my 904, or do I have to get a custom one made? Where can I buy 'em? I don't even see Lakewood's offerings for 904s on their website.

4. Alternator: 60amps okay? Should I go with stock replacement for LA or another style (I heard BBC works?)

5. Fuel Pump: Going with mechanical, but what GPH should I be looking for? Any other special things to look for?

6. Oil filter adapter. I need the stock-style one. Can I find one anywhere online?

7. Torque Converter: For a full-street car, what should I be looking for?

8. Pulley Kits: is it worth going to a serpentine drive kit? I will need to purchase all the pulleys, the dampner, the alternator, power steering pump, and all the brackets and belts anyway.
 
sharpie said:
Hey all, I am getting into the final stages of my LA/Magnum project. Still a lot of $$ to go, but I feel like it's coming together (or will be once I get those heads). However, I still have some questions:

1. Flex-plate: What am I looking for?

2. Vibration Dampner: which kind? Thin/Thick? Magnum/LA style?

3. Bellhousing: Will an LA/904 housing work for my 904, or do I have to get a custom one made? Where can I buy 'em? I don't even see Lakewood's offerings for 904s on their website.

4. Alternator: 60amps okay? Should I go with stock replacement for LA or another style (I heard BBC works?)

5. Fuel Pump: Going with mechanical, but what GPH should I be looking for? Any other special things to look for?

6. Oil filter adapter. I need the stock-style one. Can I find one anywhere online?

7. Torque Converter: For a full-street car, what should I be looking for?

8. Pulley Kits: is it worth going to a serpentine drive kit? I will need to purchase all the pulleys, the dampner, the alternator, power steering pump, and all the brackets and belts anyway.
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Wow, lots of questions!
I am going to assume that this is a 360 block.

1. You need a 360 flex plate for a LA
2. A stock dampner for a LA will work fine
3. Stick with the LA style bellhousing
4. The altenator will depend on your wiring, if you did not upgrade the wiring, do not upgrade the alternator. They are cheap at the local parts dealer.
5.A stock mechanical will work fine unless you have really hopped up the engine.
6. I used a straight out of the block adapter and it was fine with my headers.
7.I don't know what your running for a cam or gears but if you haven't overdone in those areas, I wouldn't go anymore than a 2200 stall.
8. I would stay with the stock style otherwise you will run into rotation direction problems with the waterpump and or the power steering.

Hope this helps.

Jack
 
Coyote Jack said:
Wow, lots of questions!
I am going to assume that this is a 360 block.

1. You need a 360 flex plate for a LA
2. A stock dampner for a LA will work fine
3. Stick with the LA style bellhousing
4. The altenator will depend on your wiring, if you did not upgrade the wiring, do not upgrade the alternator. They are cheap at the local parts dealer.
5.A stock mechanical will work fine unless you have really hopped up the engine.
6. I used a straight out of the block adapter and it was fine with my headers.
7.I don't know what your running for a cam or gears but if you haven't overdone in those areas, I wouldn't go anymore than a 2200 stall.
8. I would stay with the stock style otherwise you will run into rotation direction problems with the waterpump and or the power steering.

Hope this helps.

Jack
Click to expand...


Thanks for the answers. It is indeed a 5.9L Magnum motor. An LA dampner is different than a Magnum dampner, is it not? Also, I was kind of wondering where to find the oil filter adapter (other than the junkyard), and was trying to find out what fuel pump people are running, since I don't know what the stock specs are.
 
I am a little confused. The typical definition of a LA/magnum hybrid is a LA short block with magnum heads. Based on that definition Jacks response is correct.

If you have a magnum motor then all the damper and flex plate balanced for a magnum is required, there is a difference in the balance between the two.

The transmission bolt circle on the back of the motor is the same between a LA and magnum so any small block 904 tranny will bolt up (a 904 has the bell housing integrated into the tranny housing so there is no separate one to buy).

What Jack said regarding the alternator. But, magnum uses a serpentine belt system with a cast mounting bracket. A 70's vintage 60 amp mopar alternator will not mount up and won't have the serpentine pulley.

The magnum motor does not have provisions for a mechanical fuel pump. If you want to use a mechanical fuel pump you will need to swap a front cover from an LA motor onto the magnum and use a LA water pump (magnum won't fit because of the reverse rotation). If you are using a magnum cam you will need an adapter that will allow the mounting of the fuel pump eccentric. By going to this front cover then you can use the older 60 amp alternator with mounting brackets an pulleys from a LA motor that match the accessories you plan to use. Or you can go with an aftermarket serpentine system.

Not sure what you mean by oil filter adapter. The oil filter mounting plate that is on the magnum block is the same as the LA and no need to change it. If you want the 90 degree adapter they are available from Mopar Performance.

The torque converter is a function of the rear end gears and cam you are using, pick the stall speed based on the cam recommendations.
 
I guess I should tell everyone what I'm running. I always thought a Magnum/LA Hybrid was what I was using:

Magnum roller short block (block, pistons, crank)
Magnum roller cam, lifters, rods
Magnum heads with pedestal-mounted rockers that oil through the rods
Magnum carbureted intake manifold
LA oil pan
LA timing cover
LA mechanical fuel pump
LA alternator
LA power steering pump
LA 4-BBL carb
LA kickdown linkage
(Magnum or LA?) dampner
(Magnum or LA?) flexplate
LA headers
LA water pump
LA motor mounts
LA belt style (assuming I don't move to serpentine, which sounds like I won't be)

So if the transmission has the bellhousing built in, I'm really in a bind with my slant six TF904 that I have right now, aren't I?

About the old filter adapter - I guess I was also using a misnomer there too, I meant the mounting plate. The block I got came without the plate and the double-ended hollow tube/stud that the oil filter screws onto.
 
With that setup you will need magnum damper and either a magnum balanced flex plate or a neutral balanced flex plate with a magnum balanced torque converter. With an external balanced engine the damper and flex plate must match the internal rotating assembly.

For your oil filter adapter you will need to make a junk yard run or buy new through the dealer. If you go to the junk yard find a LA motor with power steering and grab all the pulleys and brackets, that will ensure that everything will fit.
 
dgc333 said:
With that setup you will need magnum damper and either a magnum balanced flex plate or a neutral balanced flex plate with a magnum balanced torque converter. With an external balanced engine the damper and flex plate must match the internal rotating assembly.

For your oil filter adapter you will need to make a junk yard run or buy new through the dealer. If you go to the junk yard find a LA motor with power steering and grab all the pulleys and brackets, that will ensure that everything will fit.
Click to expand...


thanks for the info! Any help with a fuel pump though?
 
Use the LA cover and buy the adapter to run the mechanical pump. The nose on the magnum cam is too short to run the eccentric.
Moly coated is a good idea.
 
I'm buying a custom grind Comp hydraulic roller cam with the snout of an LA on the core.
 
71DartGuy said:
If you do you cant use the magnum lifters and push rods.
Click to expand...

And why is that?

Unless there is something I am not aware of if he gets a roller LA cam there should be no reason why it won't work.

Magnum cam into LA block with the expectations of using the LA shaft rockers won't work because the cam won't provide oil through the block to the shafts.
 
dgc333 said:
And why is that?

Unless there is something I am not aware of if he gets a roller LA cam there should be no reason why it won't work.

Magnum cam into LA block with the expectations of using the LA shaft rockers won't work because the cam won't provide oil through the block to the shafts.
Click to expand...

I thought he was buying a flat tappet LA cam to use with the Magnums roller rockers, which I understand dont work together. You're right Dave, I dont see any reason why the LA roller cam wont work.
 
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