Lets talk magnum heads

[fastback340]

Im trying to put together a list of parts that work on these heads.

Valvesprings, Rocker,valve covers, valves. Anything that will interchange from other makes and models. My reason for this is because Im going to be swapping a set on my 340 soon. Im running a CompCams XE274H and Im having a real hard time finding valve springs.

Mopar sells the R/T spring. however this spring is right at its limits with my cam and may have coil bind and/or valve float problems. If I was running a XE268H They would work. However you need to swap to 2.2/2.5L retainers with these springs.

the Mopar "6062" spring also works with magnum heads but is to stiff for my cam. It also requires machining of the seat and a differant retainer. Anyone know what retainer to use with this spring ?

Another valve spring choice is to machine the seats to run LA valve springs. this would seem like the thing to do but again what retainers to use? You can't use LA retainers becuase the valve stems are 8mm

Ive heard that you can use CompCam beehive springs #26918 with retainer #772. Still looking to find out if the seats need to be cut to run them.

Rocker Arms

The Magnum arms Ive checked have the same part# as chevy arms. So you have plenty of choices there. You'll need 3/8" screw in studs and guide plates. I'll add part numbers later.

What about Stud girdles ? Anyone try running a set on magnum heads ? When I get my heads I'll measure the stud spacing. If its the same as the Chevy spacing they should work assuming the fit under the valve covers.

Pushrods.
Mopar sells a set of of push rods for converting LA to Magnum heads

Ive also read that Boss 302 push rods work. I'll look in to that some more also.

Valve covers.
You can use production Magnum or Mopar Performance covers.
Ive seen LA covers used also and this is what Im going to do.
Again Chevy cover work with alittle bit of filing the bolt holes.

Intakes. A few choices here.
Shell out almost $300 for a Mopar Perf. M1 single or Dual Plane or an Edelbrock AirGap.
Professional Products AirGap for around $175
Redrill your heads and use any LA intake.

So thats what I know about Magnum heads at the moment. Anyone have anything to add or comments ?

[LA360Dart]

Hi fastback340;

A few things to watch for push rod to intake on head can get tight you may need to clearance them at parting line and pushrod hole. The lifters need to be oil type AMC, HT2011 is aftermarket number. Valve covers either will work. I use as cast Mopar perf. and put allen set screw in unused holes. Have not tried chevy stud girdle yet not enough valve spring pressure to worry about. Avoid comp cams guide plates as close but will break off ear on plate ( oldsmobile ), use crane type of guide. The heads can be drilled and tapped to use LA intake. Tyco just cut a tube at a angle to match intake then cut at 90 deg. and elongated intake to allow vertical mounting of LA intakes so that intake could be used on either. Aftermarket makes taller retainers up to .125" but guide might still hit retainer before coil bind occurs my limit is .540 lift currently .511 with 230 @ .050 duration. Next step is to cut spring seat and PC seals to gain more lift. As always check all clearances before final assembly. Also with better balance on cylinder head you should not need split pattern cam as exhaust is within 75% of intake flow on the magnum heads. Split pattern cams correct for poor balance on LA heads.

Denny

[cageman]

I have the imitation airgap, it has both sets of holes in it and it is a really nice intake, fits in my valiant with a holley and a 4 inch air cleaner, sweet.

[Crank]

Are you talking about the crosswind manifold? they look like a nice piece and cheep ,i think polished is 20 bucks more.do yourself a favor and open up the bowls.

[BRAZILIAN MOPAR]

Anyone know the flow numbers of a stock Magnum head???

[fastback340]

unported on RyanJ's bench (Shadydell machine shop)


LIFT----AS CAST
---------IN/EX
.100"--67.3/N/A
.200"--131.3/97.3
.300"--185.6/132.5
.400"--212.5/144.9
.450"--213.9/146.3
.500"--212.2/146.3
.550"--212.5/146.3
.600"--213.9/146.6
.650"--214.2/147.3
.700"--215.3/147.3


compared to undported 596's

LIFT----I-------E
.100--62.8----48.3
.200--117.3---98.3
.300--174.2---120.8
.400--193.2---125.6
.450--192.5---127.7
.500--192.5---128.3
.550--192.5---129.0

fully ported heads. Magnums-J-Eddy RPM-MP Comandos. All heads have 2.02 valve except the magnums wich have 1.94s

LIFT--MAGNUM---"587"----EBROCK----COMMANDO
.100"--67.3-----62.1-----65.6------69
.200"--132.8----135.2----135.2-----140.1
.300"--196.0----198.7----197.7-----202.5
.400"--225.0----239.8----233.2-----246.4
.450"--238.1----253.9----245.0-----266.0
.500"--250.5----258.4----255.3-----277.1
.550"--257.1----264.9----265.7-----281.2
.600"--259.1----254.6----274.6-----282.9
.650"--259.1----N/A------279.1-----283.0
.700"--259.8----N/A------283.9-----285.3

Heres a set of fully ported Js with the stock 1.88 intake valve,

LIFT--MAGNUM---"596"
.100"--67.3---58.7
.200"--132.8--120.1
.300"--196.0--182.9
.400"--225.0--225.6
.450"--238.1--238.1
.500"--250.5--241.5
.550"--257.1--247.0
.600"--259.1--248.8

[rumblefish360]

FB340, thanks for that post. Good info. If not just to play around on the DTD sim.

[fastback340]

No problem.

[fastback340]

Spark plug recommendations

stock heat range
autolite 3924
champion RC12YC

1 step colder
autolite 3923

2 steps colder
autolite 3922