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Magnum 318 carb conversion

10-06-2010, 09:46 AM
What parts/things do I need to do to an EFI 5.2l Magnum engine in order to make it run carburated?

I know I need: Intake and carb, fuel pump, Schumaker motor mount conversion kit (slant six to Magnum).

Already done: 10" spindles and 10.8" front disk conversion.

With the fuel pump, is there a way to attach a mechanical fuel pump, or do I have to use an electric one? Is one easier to install than the other?

I have a 73 LA 318 I can pull parts from, including the oil pan. Will that work, or do I use the Magnum pan in this conversion?

I welcome advice on this, as I've never done anything like it before. Thanks for your time!

10-06-2010, 10:40 AM
For a manual fuel pump you will need an LA cover and if you have the short snout magnum cam will need the eccentric and bolt kit from Hughes, carb and intake, I think most if not all all magnum pans were rear sump, a passenger car center sump will fit but u must use LA gaskets unless you modify the pan, I'm not sure but I think you will be needing a straight electronic distributor, I dont know if the orig. dist. can be adapted. I have heard that unless you get a really good exhaust gasket, using LA manifolds on the Magnum will leak, as the port design is different enough to cause problems. Camshafts are expensive as they are the roller design. Manifold selection is somewhat limited. For the price and what you get air gap knock off professional products crosswind dual plane intake. Valve cover is very limited if u use a 10 bolt, can use the LA 5 bolt ones. Stock valve springs are good to about .500 lift. Bullet Cams can regrind your stock cam or Hughes engines has them. 200.00 exchange. Cam with a lift over .525 lift must buy new retainers to provide extra clearance, Professional Products has a inexpensive balancer that works well. If you have the complete motor I would tell you to run the original serpentine belt. On Magnum engines the flex plate is balanced to the engine (this is what the tech guy at B and M told me any way)your converter and balancer must be matched to them if you dont use the tranny with the 5.2. TransDapt mounts at summit are half or less the price of Shoemaker, work well and designed to work with the inexpensive hedman headers. Google Junkyard Jewel 360 Magnum and follow the other links from there.

10-06-2010, 10:42 AM
You will also need a distributor with an advance mechanism (the MP electronic ignition conversion will work or anyone of the aftermarket units).

If you want to use a mechanical fuel pump you will need the LA style timing cover, a snout extension for the cam and the fuel pump eccentric. Swapping to the LA timing cover will also require using an LA water pump (magnum turn the opposite direction) and all the LA accessory brackets and pullies. It would be easier to use an electric fuel pump.

The magnum engine will have a rear sump pan, if the engine is going into a car you will need a center sump pan and pick-up. I believe the 5.2 magnum has the same rear main configuration as the 5.9/360 LA so the 318 pan won't work regardless if the sump is the correct position.

10-06-2010, 10:43 AM
The Magnum cam does not have the "snout" to run the mechanical fuel pump eccentric. However, Hughes engines does sell a cam snout so you can run it if you like.

Another option would be to change the cam itself to a hydraulic roller grind that has the snout. This is what I did with my magnum swap. I didn't want an electric pump. This is a good idea either way as the stock 5.2 cam is not a performance grind by any stretch.

You will need a conventional small block dizzy, points or electronic, depending on what's in your car.

I don't know for sure if the 318 pan will work on the 5.2. I do know for sure that a 360 pan works on the 5.9.

If you are running hooker headers you will most likely have to grind down the drivers side truck engine mount to make it work.

Check the heads for cracks!

Good luck with the swap.


10-06-2010, 11:04 AM
Thanks for clarifying what I was trying to say about the snout. LX. Also On the tranny I was trying to say that unless you were running all the orig equipment if you broke the package apart and say put a 904 behind it you should research the flex plate/balancer/converter situation carefully. The switch to flat tappet is an excellent option but I have heard that it is expensive. I have also heard that the AMC and mopar lifters now carry the same part number and it is important to get the correct AMC lifters for the swap. Some of the guys who did the swap wound up having to measure and order custom length push rods. I'll stick with the roller set up for both free horsepower from a lower friction coeffecient, the ability to reuse lifters indefinitely, the chance of wiping a cam very low, and not having to use high spring pressures, and overall durability.

10-06-2010, 02:51 PM
I was suggesting hydraulic roller, not hydraulic flat tappet.

I believe the 5.2 magnum is internal balance like the LA 318. That being the case, he should be able to use any 318 flexplate, converter, balancer, etc.

The 5.9 magnum however, has a unique Magnum weight, and you have to be very careful when getting balancer, flexplate, converter, etc. parts for them.

04-24-2011, 08:17 AM
old style "la" 318 harmonic balancer work on a new style magnum 318 with the old cover?

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