Magnum Heads

bobscuda67 said
I had a very hard time finding magnum heads that weren't cracked. I had one good head out of eight that were pressure checked. The stock heads are junk and should not be used, the chambers measure 67cc's and need to be milled a lot to get the compression up, further weakaning the head. I bought the heavy duty magnum heads bare and reused some magnum valves. Had to have the spring seat cut to fit the 1.5" valve springs and the retainers are hard to find. I used Hughes springs and they have the retainers to fit the 8mm valves. Bolted on the heads and the rocker arm nearly rolled off the edge of the valve. Installed lash caps and the geometry is a lot better. I used the Crane chevy roller rockers and they fit like crap. Had to grind a wider slot to clear the stud.
Not much of a choice of intake manifolds either, you should use the angled I would just call Hughes Engines and order there heavybypass hose intake. I found a Mopar M1 dual plane that I'm using.
The magnum accesory holes are a little bit different causing alignment issues.
I havn't even started the kickdown and throttle cable yet.
A lot of the problems are due to me trying to save some money.If I had to do it all over again I would just call Hughes Engines and order there heads and rockers and studs, guideplates. Bob

More often than not the cracks that folks see in these heads are a cosmetic issue and have no detrimental effect on the operation. Engines run for 100,000's of miles with cracks. For sure you need to make sure that they aren't compromising the water jack or the ports but a small crack on th surface is not a reason to discard a set of heads.

There are quite few spring options that do not require cutting the seats. MP has two springs, one good for .525" lift and another for .600" lift, a little pricy compared to other springs but not if you factor in cutting the seats. Retainers for these springs are dirt cheap and in most cases can be had for zip. Just harvest them from any 2.2 or 2.5 mopar 4cyl. Comp now has a drop in beehive spring for magnum heads but I do not know if the stock retainers work. the GM3800 v6 spring is a drop in and the retainers are for 8mm valves, these are dirt cheap also but are only good for cams in the .480" lift range.

If you want to use Chevy roller rockers you will need to get longer pushrods. The chevy 7.8" push rod worked well for my motor but unless you are planning on reving past 6000 rpm all the time the stock stamped rockers are more than adequate.

Granted there is not a lot of choices in manifolds but really how many do you need? MP has a single plane and a dual plane. Edelbrock has their Air-Gap in a magnum bolting and the Professional Products CrossWind will bolt to either LA or Magnum heads. Wouldn't be surprised to see the new Weiand Air-Strike in a mopar version soon either.

I don't know why folks keep saying the accessory holes on the heads do not line up. I have been involved now with my LA/magnum hybred, a 380HP crate moter into an A-body and a 300HP crate motor into a B-body and there were no issues at all with the alignment of accessories. Everything just bolted on and lined up.