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Anybody convert 5.9 magnum to carb

Started by A.Gramz, March 10, 2019, 07:09:54 PM

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A.Gramz

Looking to see if anybody has used a 5.9 magnum with a carb setup.  I see they sell conversion kits. Woundering how it performs.

Chryco Psycho

I did one a few years back , worked great , the oil pan & intake are unique

A.Gramz

@Chryco Psycho. Well that's good to hear.  I have a few questions that maybe you could help answer or clarify then.   Pls keep in mind I'm way over budget on body and paint. So engine can always be upgraded later shooting for 300- 350 hp and torque numbers
  For intake I could use a la eng one just machine mount holes for studs?

I was under the impression the magnum has a truck pan on it but the la car pan would fit?

Now I want to keep mechanical fuel pump. So will a LA cam, timing cover, water pump bolt to a magnum or is that all magnum specific coverstion parts I need to buy. 

I believe the balancer is special for this conversion is that correct

I'm sure I have more questions but I'll start there.  I no some of these might seem basic but carbs were being replace by efi around the time I was born and I'm a desiel mechanic so it's a bit different.
Thank you Adam


Chryco Psycho

We used a special intake with the holes drilled at a different angle for the Mag heads , but you could stud it & carefully drill an LA intake
The oil pan is the big glitch , the LA pan has different diameter end seals from both the 318/340 & 360 pans I forget what we used maybe Milodon as there is no magnum car pan .
As I recalll the magnum can nose is different & will not support the pump drive cam
yes the balance is different on the Magnum

jimynick

Neil is right about the cam, as they use a "short" version that has no fuel pump eccentric on it. Having said that, an aftermarket cam can cure that, and I bought a hyd. roller with a "long" nose and eccentric from Lunati with no problem. Just use a LA timing cover to get a fuel pump mounting boss. You guys do have me now worrying a bit over this oil pan deal and I'll have to check it out further. I also believe you can buy a carb intake for the Magnum from Summit for about $390 for the Edelbrock  7577 Air Gap version if you use the Magnum heads.  :cheers:
In the immortal words of Jimmy Scott- "pace yourself!"

YellowThumper

Quote from: A.Gramz on March 11, 2019, 10:47:08 AM
@Chryco Psycho. Well that's good to hear.  I have a few questions that maybe you could help answer or clarify then.   Pls keep in mind I'm way over budget on body and paint. So engine can always be upgraded later shooting for 300- 350 hp and torque numbers
  For intake I could use a la eng one just machine mount holes for studs?

I was under the impression the magnum has a truck pan on it but the la car pan would fit?

Now I want to keep mechanical fuel pump. So will a LA cam, timing cover, water pump bolt to a magnum or is that all magnum specific conversion parts I need to buy. 

I believe the balancer is special for this conversion is that correct

I'm sure I have more questions but I'll start there.  I no some of these might seem basic but carbs were being replace by efi around the time I was born and I'm a diesel mechanic so it's a bit different.
Thank you Adam


I have basically done what you are asking in reverse. Magnum accessories on a LA. I have started a thread here with some of the details listed.
Starting with manifold. They sell aftermarket intakes that have the carb mounting. Was also told in the past (but not confirmed) they make "conversion" manifolds for Magnums with the LA thermostat housing locations. Thermostats in Magnums were relocated. AC compressor now resides where old one was.
Magnum intake mounting bolts are vertical. Not angled towards the heads as the LA heads are. They however, do come thru the manifold face in basically the same location. See my thread... 74 Challenger with twins in the build section.
https://forum.e-bodies.org/your-restoration-project-roseville-moparts/10/74-challenger-with-twins/9837/

Worked to re-drill intake for what I am doing but am unsure it would work in reverse. I do not believe Magnum head could be drilled to match LA pattern.
Possibly add bosses to LA intake to allow drilling of Magnum mounting holes.
Ports and water jackets remain in same locations.

Yes, the LA timing chain cover will mount properly on the Magnum. I mounted Magnum to LA.
Crank sealing diameter is the same. I believe its location fore and aft is also the same.
No to mounting the accessories. Most all other bolts to the heads and block are either in different locations, sizes and/or have different fore/aft positions.
It can be done but you will have to do some fabrication.

When I mounted cover, I just left the original fuel pump eccentric bolted to the cam because it cleared everything.
IIRC you will be required to either change out your cam or drill it for a pin to mount and time eccentric (Just to stop it from spinning) for manual fuel pump. With this you would be better served to go electric.

As far as the pan being different. I am not sure of the differences. I purchased a new Magnum pan that is supposed to fit my car from Bouchillon performance.
I can say though that the front pan seals that goes below crank are the same because the timing cover fit as it should have.
again IIRC there were a couple of those pull thru the pan holes rubber locator s that I needed to
You will need to keep the Magnum harmonic balancer as the weight is different. However the face location fore/aft was the same along with the 6 bolt pattern to mount the bottom pulley.
I bolted on the bottom serpentine pulley to the LA balancer with no changes and it lined up (again fore and aft) correctly with all the other Magnum accessories.

All in all it can be done. But will never be exact if that is what you are looking for.
If going Magnum, go all Magnum for accessories along with electric pump.
Simple easy serpentine system that is also newer.
Going carburetor can just be a manifold swap.

If you want AC then things get tricky again for the upper radiator hose. see pic and also on my thread.

Purchase a new pan that will work for your setup.

ALSO... There is a difference in the left (drivers side only) motor mount bracket between the LA 318 and LA 360s. 340 I have no knowledge.
Simple spacing (not location) issue for the rear bolt on the bracket. Rubber mounts are the same. LA 318 brackets will still bolt up to a LA360 with a spacer. I used a stack of washers to correct when I changed from LA 318 to LA 360 long ago.
I believe the Magnum also follows the LA 360 mounting spacing.
Life is to be viewed thru the windshield. Not rear view mirror.
You are the only one in charge of your destiny.

Mike.

Chryco Psycho

It is the rear oil pan seal that is different between Mag & LA
I agree that electric fuel pump is a better solution but mechanical can be done
the manifold we used had dual pattern , you could drive buttons into the unused holes & as above they holes are basically in the same location but at different angles
340/360 use the same left mount , 273/318 were different


YellowThumper

Quote from: Chryco Psycho on March 11, 2019, 09:22:14 PM
It is the rear oil pan seal that is different between Mag & LA
I agree that electric fuel pump is a better solution but mechanical can be done
the manifold we used had dual pattern , you could drive buttons into the unused holes & as above they holes are basically in the same location but at different angles
340/360 use the same left mount , 273/318 were different

Thanks i will try and retain that this time...
I suspected 340 was same as 360.
My assumption why they changed it was to move the stress point farther away from the larger bore motors. Just a theory.

If end goal is to have everything appear stock I agree it could be done to "mostly" look that way.

ALSO flywheel counter balance also has to change from the LA version. I also purchased proper weighted flywheel (4 spd) from Bouchillon.
Life is to be viewed thru the windshield. Not rear view mirror.
You are the only one in charge of your destiny.

Mike.

Chryco Psycho

The strength with Mopar blocks is the mount is tied into the front wall of the block , , chev did not figure this out , the mount was in the center of the side of the block , same with furd , the torque will distort the block there & cause early failure , the Mopar block are also much taller & thicker for more strength , also much higher nickle content , porting Mopar heads is slow with the high nickle content , other makes cut like butter by comparison  :alan2cents:

b5cuda

For more info/experience you might want to check for a-bodies only forum - lots of a-body guys have swapped in Magnums.

A.Gramz

Thanks guys lots of info here to try and retain.
I have my contacts looking for a good take out.  So I'm just waiting.  Once I tare into it im sure to have a whole new set of questions.