magnum head question

Yeah it doesnt actually take much to convert them. All you need is the heads, an intake that'll fit them, the conversion pushrods from mancini, rocker arm assemblies with plates (which you can get from hughes or from chrysler), magnum specific head bolts (also from chrylser), magnum valve covers (also from chrysler or used), and the throttle/kickdown bracket for magnum intake from mancini (i just bent my LA one a bit and it fit fine though).
Everything else other than that is standard LA equipment.
Don't forget that those magnum rockers are 1.6:1 ratio. I put a factory 340 cam in my magnum swapped '84 360, and the rockers bumped it up to .459/.472 lift with the same duration. It has come serious bottom end to it, idles at 18 inches of vacuum, and moves my W-250 around great. In an A body that motor would fly. I range it at about 310hp. My heads are also the largest valved of the 3 encarnations that came from the factory. I got a SCREAMING deal on them on eabay. 160 bucks plus shipping rebuilt, and they came with the valvetrain, and valve covers (a guy had sold a car before doing the swap and was selling off his swap stuff)

Anyways, I recommend you do it. Its not all that expensive and the power gains are great. Shoot, my compression is even 9.5-9.7:1 now. Plus its still nothing super aftermarket or outlandish like aluminum heads etc. It's still all factoryish stuff.

Wow a couple interesting posts here

"you will gain at least 100 hp. the competition cam will provide power, reguardless. they are good at that. with flat tops and 10:1 compression it will hunger for 94oct on hot days.

im maybe thinking, its making advertised hp 450.

horsepower @ .050 350hp. "

Make that about a 25hp difference in the stock 360LA heads VS the magnums. You will gain some tq and MPG from them also I have no idea what HP @.050 means so I can't guess at that but depending on what a "small comp cam" is 400 hp should be a piece of cake. The XE268H would be a good choice, it is basically a step up from the factory 68 340 4spd cam. It will make decent vacume and a factory high stall converter will work great.


Also there is this,

"My heads are also the largest valved of the 3 encarnations that came from the factory."

Don't worry about valve sizes, magnums only left the factory with 1.94 1.625 valves. Combined with there 5/16 stems they flow every bit as good as an X head with 2.02 valves. There extra power comes from effiecncy They will out power factory 1.88 valved 360 heads by a bunch and will flat kill a 318 sized 1.75 valved head.

"My heads are also the largest valved of the 3 encarnations that came from the factory."

Don't worry about valve sizes, magnums only left the factory with 1.94 1.625 valves.

There are 3 different castings of magnum heads from over the years. look it up. And the larger valves are like .002 bigger, so it isnt mouch of a difference. But yeah magnum heads do just fine out the factory door.

Hmm now MP magnum R/T iron heads would be even better

technically all factory magnums came with 1.92/1.625 valves with 8mm stems.

You will see a power gain due to increased compression. How much will depend on everything else in the combo. In any case, the added torque and HP will be noticable.
Magnum heads are a bolt on with the proper parts. Things you will need are; head bolts, valve covers, oil through lifters (AMC style), oil through pushrods of the proper length. You can have the heads redrilled to accept the LA intake. I will assume that the heads you get have the 1.6 rockers already.
Things to watch for are; the size of your cam. If it has any more than .525 lift using the 1.6 rockers you could have a real problem with retainer clearance. The stock springs may be a little weak if you have more than .475 total lift.
I run 10.58 to 1 compression and a Comp Cams Magnum 280H and have no detonation using mid-grade gas in my LA/Magnum 360. I also have 400+ HP.

Jack

i have a xe268 laying around. gna throw that in. sounds like it may be a lil peppy engine. well gna start reading and getn sum parts. thanks all

the approx .8:1 compression increase the ~9cc smaller chambers the mag heads give will increase power by about 3-4% alone on a stock 360 short block over standard LA 360 heads, not considering the better combustion chambers, larger curtain area of the valves, and better flowing ports. comp XE268 wouldn't be a bad cam for a light car with a stock 360 shortblock/mag head combo, if it's a heavier car I'd drop down to an XE262.