Cracked Magnum Heads - Junk or Not?

Magnum Engine Swaps

  1. Idaho

    Idaho Well-Known Member

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    These came off a 5.9 Magnum that will be getting a set of RHS heads for my project. They are a reman head, mileage uncertain as I'm not sure when in the 78,000 mile life of the truck they were installed.

    With 2.0 reading glasses and a magnifying glass I was able to detect cracks between the valves of cylinders 1 & 2. I was able to feel them with the sharp edge of a razor as well. Of course there could be other cracks I could not see.

    Apparently these cracks do not alwayse affect performance. This engine was reported to be running perfectly before the truck was rolled. It seems likely a lot of the Magnums in operation have these cracks.

    I put the post up to get a feel for whether I should bother to list them for sale or trash them. It's also just an interesting discussion about the cracked head issue.

    One of the pics that's not in good focus happens to show a crack by some fluke of lighting. In the close up, its there in the middle, might be hard to see (use the eye of faith :)

    Also interesting, the reman was done in a Cummins plant in Canada.
     

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  2. 67 gt

    67 gt A Wog boy who loves his Mopars ! FABO Gold Member

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    Try a set of EQ Magnums which have been rectified with the cracking issue.
     
  3. Idaho

    Idaho Well-Known Member

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    My understanding is EQ and RHS are very similar. For me it comes down to getting a complete package with quality components and build. I'm planning to purchase from Brian at IMM.

    If I recall, the EQs are cast in your neck of the woods, correct? Not sure on RHS.
     
  4. Abodybomber

    Abodybomber Breaking street machines , since 1983.....:) Legendary Member

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    Idaho,two words. "pressure test"
     
  5. moper

    moper FABO Gold Member FABO Gold Member

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    They are probably fine - but you'll ahve to convince the buyer of that. Get them pressure tested and have that handy for the buyer. It's common to have them crack, and no - it isn't fatal.
    The EQs are very different from the RHS heads. The EQs are basically stock Magnum design, with stock Magnum ports, stock Magnum rocker gear, a thicker area where the visible cracks appear, and variable bolt patterns (order the type you want - stock Magnum or stock LA patterns).
    The RHS heads are a performance head casting, based on the Magnums. The ports are different and better, and are cast with provisions for both rocker setups. You order what you need - LA-X heads are the LA intake pattern and LA shaft rocker system machined for use. The MA-X heads are the Magnum pedestal type rocker system and magnum intake pattern.
    Both are limited as far as lift goes without using longer valves and the right rocker setup. The RHS castings are heavier by a bit because of the extra material cast into them.
    I like the EQ heads with the LA intake pattern for 273 to 340 builds that are milder (under 350hp or so). The RHS heads are for larger engines with the need for more lung capacity: up to about 425hp. Beyond that, once any porting is needed or there's racing involved - IMO you've outgrown these two head designs as far as cost vs return.
     
  6. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    We threw cracked engine parts in the scrap pile 30 years ago. I still do.
     
  7. jos51700

    jos51700 Hemi Orange you glad it isn't a political avatar?

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    I'm not here to cause a fight, but Moper says the EQ heads have stock ports.

    I don't know, I've never seen the EQ heads in person, but Mopar Action did a flow test blowout a couple years ago and flow was up quite a bit on the EQ over the factory Magnum head.

    Not saying Moper is wrong, but saying it might be worth finding that article (there's an index on moparaction.com) and seeing for yourself.
     
  8. TrailBeast

    TrailBeast AKA Mopars4us on Youtube

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    I personally would not use a head that had a crack under the compression ring no matter what anyone said.
    Between valves, yes if they didn't leak into the water jacket.
    On the compression ring area, no way.

    It WILL blow the ring between the cylinders.
     
  9. metallidart

    metallidart member me?

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    I think as long as it was a small crack between valves, and other than the actual crack thereis no evidence it was having issues because of the crack, I wouldn't hesitate to use a cracked head on a budget magnum build. I have adapted the magnum head stand-by "use the cracked ones on your own engine, they will be fine, sell the non-cracked ones" lol. Then again, I am a "lets see what happens" kind of guy.
     
  10. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    Keep in mind, moper speaks from real world experience. Those magazine articles are jaded into making sure their sponsors look good. I take anything in magazines with a grain of sand anymore. moper doesn't have to blow up the skirt of any sponsors. Keep that in mind.
     
  11. Idaho

    Idaho Well-Known Member

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    Thanks, that's some very useful information. More than I came up with searching for info online. I'm not sure what you mean by that last sentence. Could you explain?

    If I were considering using them myself I'd do that. Not worth the bother and expense for what they will sell for.
     
  12. Oldmanmopar

    Oldmanmopar Going left turning right FABO Gold Member

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    My wife has a crack. What should I do?
     
  13. whitepunkonnitro

    whitepunkonnitro Well-Known Member

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    I wrote for the magazines...hell, I started some of them! And you're right...it's all bullshit. That's why I stay away from them anymore.
    As for those heads, I would bolt those on without even thinking about it. I've run stuff like that in everything from grocery getters to Top Fuelers. Not all cracks are created equal. It takes experience to know what you can get away with and what is scrap. The pics the OP posted show heads that are good to go for nearly any application.
     
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    • Dodge74

      Dodge74 Well-Known Member

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      They can be fixed. But it's up to you if you want to use them again......
      Once they drill and pin them they are good as new,i have seen it done
      IMO if used in stock form ok re use them but not in a performance setting
      your better off spending the money on some EQ's .......................

      Thanks..................PETE......................
       
    • 1wild&crazyguy

      1wild&crazyguy Banned

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      Just fill her crack with some caulking... ;)
       
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      • whitepunkonnitro

        whitepunkonnitro Well-Known Member

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        The ones he's showing there do not need to be repaired. I've pinned and welded more cylinder heads than I can remember. I even developed my own method for repairing blown out Hemi chambers that I torture tested blown on nitro, so I know a thing or two about this. Trust me, those heads he is showing are literally good as new and will go a zillion runs in a 9 second car without ever so much as sneezing. Regular street driver? Those are good forever.
         
      • 1wild&crazyguy

        1wild&crazyguy Banned

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        If you put hard seats in those, int and exhaust.... Then there's probably nothing to worry about.

        But if you only install hard exhaust seats and that crack is towards to int seat enough...it will come back into the int seat and cause issue.
        Ablot of x,j,u,o, or whatever heads have a lil crack on the plug boss, never an issue though.

        Heads can be repaired and be ran longer than the owners lifespan in a lot of cases.
         
      • 1wild&crazyguy

        1wild&crazyguy Banned

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        I have had j heads pinned and run full ported on 10 .1 comp motors spinning 7 k.
        I have had slant heads plugged between cylinders, no big deal.
         
      • RustyRatRod

        RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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        All of the repair comments are true, no doubt, they can be repaired. However, cast iron is funny stuff. It can crack anytime it damn well wants to, even after a professional repair. That's the part of the equation that's uncontrollable. I would rather run something with no cracks. But that's just my own personal opinion.
         
      • moper

        moper FABO Gold Member FABO Gold Member

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        First - to clarify - I have submitted to a magazine before. For all I know it got tossed within seconds because they sure never called me but there's not much call for rearview mirror repair articals...lol. Also - I can and do blow up skirts - but not a car magazine's :D
        The EQs are shipped bare. The shop where I saw them (they do my machining now) has used many sets on class circle track engines over the years and they work like mad - when matched with the right components. The better flow numbers come from a much better casting quality, a good valve job, and performance valves. There is no "out of the box" flow ratings because they don't come assembled - just like the RHS heads - and if you think a top notch performance valve job isn't worth an additional 5% flow and better cylinder sealing you are paying the wrong people to do it.

        "I'm not sure what you mean by that last sentence. Could you explain?"
        These heads are iron, and limited by minimum cross section due to the pushrod pinch. They flow well - very well - for what they are. But as soon as you have to start whittling to get more air though them, the costs go up because iron takes twice as long or more to port than aluminum, you can't just hog them out and get huge numbers, and ultimately the iron heads are heavier than the aluminums. So once you have to spend more cash, the aluminums - IMO and using my local pricing anyway - are more overall cost-effective.
         
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        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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          More cost effective and more potential. Win win.
           
        • 1wild&crazyguy

          1wild&crazyguy Banned

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          We all have great points, but is he asking what head to buy or is he asking if these old heads of his can be made good to sell to someone else to run for x amount of miles?
           
        • crackedback

          crackedback FABO Gold Member FABO Gold Member

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          The RHS will support more than 425hp, especially if you install a 2.02 valve.

          There are many unported rhs heads on 360's and 400 inchers making 485+ and some in the low 520's.

          Pick your parts, pay your money.

          Some of those cracks in mag heads aren't anything, others are more serious.
           
        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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          Good point. Thanks for the reminder.
           
        • Idaho

          Idaho Well-Known Member

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          OK, I get it. Makes sense to me. I'll comment further below.

          The post title says it :) I think the question has been answered well enough. I'll put them up for sale cheap. But the conversation is informative. It's interesting to see the different perspectives. So I'll keep it going a bit...

          I wanted from the beginning to go with aluminum heads. Aluminum appeals to me for the reasons stated. I decided on RHS based on these considerations:

          1) I'm doing the junkyard 5.9 build. For the Eddies to make sense, seems I'd need to change the pistons for higher compression, hone etc. The pistons are not cheap.

          2) I'm told the Eddies should be "gone through". This one bugs me. I suspect many are just bolted on and do fine, but the advice comes from respected folks so I don't want to ignore it. Hard for me to know what that adds to the cost.

          3) Moderate performance goal (400 HP range). RHS heads should get me there with some peace of mind regarding quality.

          I think if I go for much more power, I risk breaking things, especially with a 4 spd. The overall cost potentially gets out of hand.

          One thing I should look at. What do the Eddies need for rockers?

          I'm planning to do the Hughes shaft rocker system on the RHS heads which of course is a substantial added cost.
           
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