Head gasket recommendations for magnum

Small Block Mopar Engine

  1. schwinger

    schwinger 1972 Dodge Dart Swinger

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    I had another thread earlier last month about a possible intake manifold leak on my 5.2 magnum in my 72 dart which I thought I fixed but after taking it for a drive noticed a proof of white smoke coming from the exhaust coming from a stop light and was in oh crap mode thinking it was the gasket I installed which I didn’t think that was the problem or a blown head gasket so rented a boroscope from azone and checked the cylinder that had the oily plug and it was clean but slightly green. Checked that cylinder with the boroscope and saw a puddle of coolant in there which made my day a happy go shitty day. Took it all apart and found out the head gasket blew. Go figure. The head gaskets I used was a DNJ brand which I was sceptical of since I never heard of them before at the time but gave them
    a try and but not to confident on there gaskets since the engine only has about 10k miles on it. Wondering if the felpro 540sd head gasket is a good option or what do you guys recommend and also head gasket needs to be .050 or higher compressed thickness.
     
  2. Garry in AZ

    Garry in AZ Building a 9 second Valiant FABO Gold Member

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    I have had good luck with MLS (multi layer steel) gaskets from Cometic, FelPro and JE. The Cometics are 0.075 thick when compressed.
     
  3. Blackhatguy

    Blackhatguy Well-Known Member

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    Why it's got to be .050??
     
  4. schwinger

    schwinger 1972 Dodge Dart Swinger

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    Piston to valve clearance is close
     
  5. Blackhatguy

    Blackhatguy Well-Known Member

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    You deck the block? Flat tops with no valve pockets? High lift cam?
     
  6. schwinger

    schwinger 1972 Dodge Dart Swinger

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    Block has been decked and has .020 over flat top pistons, no valve reliefs, Cam is a .490/490 lift with 108 lob separation. I bought the short block part from a guy that was gonna build it up but he never got around to it, never said how much it was decked. Heads were rebuilt from a shop that i believe they surfaced the head, cant remember. Do remember It was somewhat of a rush build since i was wanting to drive my car to minnesota at the time and the cam supplier recommended this cam so put it together and ran great untill now.
     
  7. Blackhatguy

    Blackhatguy Well-Known Member

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    Put playdough on the piston and two bolts in the head with no gasket, turn it by hand see if it hits. Then you can verify pushrod length when you settle on gasket thickness. MLS be the strongest gaskets.
     
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    • yellow rose

      yellow rose Doctor of Thinkology.

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      I can't believe you are anywhere near close on valve clearance with that cam. Even without reliefs.

      Do the clay method and check it with the springs you run in place.

      Edit: if you do need the .050 gasket there is a Fel Pro gasket that will be just fine. I can't remember the part number but someone here will have it for you.

      Also, you need to figure out why the head gasket failed. You are detonating it, the surface finish wasn't correct or something.
       
    • Tinmannz

      Tinmannz Well-Known Member

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      How far down is the piston in the hole, or is it even with the deck? Get #1 at tdc and measure it. If its beneath the deck I think .050 is too much. Even with a cam that has .490 of lift (which isn't much) you could go to a skinnier gasket.

      Correct me if I'm wrong, but don't you want quench to be somewhere between .035-.045? (I.E. piston even with the deck at .000, a gasket between .035-.045 would give you perfect quench and eliminate detonation while running on pump gas. If the piston is higher than the deck, then the gasket thickness should be increased.)

      I don't think you'll have valve interferrance with .490 lift, but you do want to check to be sure before you button it up.
       
    • schwinger

      schwinger 1972 Dodge Dart Swinger

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      Ill do the clay method and check it out. I think I was just cautious about the piston to valve clearence at the time since I’ve read about other builds being close with flat top pistons. I remember it did detonated a couple times when I really got on it but let off quickly. Maybe it took a toll on it. Also I figure since the previous head gasket was .050 compressed I get somewhat of the same but will check the clearence tho
       
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      • schwinger

        schwinger 1972 Dodge Dart Swinger

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        Ok was finally able to check the piston to valve clearence and found out the exhaust valve hit the piston. This is without the gasket by the way and the intake barely hit when I spun it the other way... I checked the lift on the cam with a dial indicator to make sure the cam is what it is, and I got .302 intake and .316 exhaust, multiplied that by the rocker arm ratio and got .483/505 . So that’s off a little but this is got me wondering. The piston is .049 in the hole too. I did advance the cam on the crank 4 degrees but I never did degree the cam which looking back now I should of.
         
      • MOPAROFFICIAL

        MOPAROFFICIAL Well-Known Member

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        540sd is .054 compressed ime.

        It's a fine gasket for 11.1 or lower

        Sounds like you need to fly cut the pistons for valve clearance, buy pistons.
         
        Last edited: Sep 24, 2019
      • Blackhatguy

        Blackhatguy Well-Known Member

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        If the Piston is 49 in the hole, and you need at least 40 to the valve, you got no quench and be prone to ping. If you have the time and resources, I would be getting a valve pocket cutter and making room for those valves. You will need to find out just exactly how much room do you need and see if those pistons can take that deep of a cut. Otherwise I'd be looking at different pistons. In an ideal world you would have zero deck, ample valve relief, and 40 thousandths head gasket.
         
      • yellow rose

        yellow rose Doctor of Thinkology.

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        Is that with the springs you use and zero lash?? Something isn't making sense to me, but that's not unusual.
         
      • schwinger

        schwinger 1972 Dodge Dart Swinger

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        I’ll look into doing that. Can’t remember the brand of piston but hopefully it’s marked on top of the piston or something.

        I wanna try to avoid that but if I have to I will or mane change the heads.
         
      • schwinger

        schwinger 1972 Dodge Dart Swinger

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        No I just put the dial indicator on the lifter itself, not the center but top ridge of the lifter and measured how much lift by turning the engine over until I reached max lift then multiplied that to the rocker arm ratio of 1.6 which I’m pretty sure thats the ratio these magnum engines have unless I’m mistaken.
         
      • yellow rose

        yellow rose Doctor of Thinkology.

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        I'm trying to understand how you can measure piston valve clearance with just a dial indicator and measuring lift. I'm lost. How do you know the exhaust valve is hitting? Witness marks on the piston? Bent exhaust valve?

        The best way to measure valve clearance is with clay on the piston, the valve train on and using the exact spring you are using. You can run as little as .040 on the intake and .070 on the exhaust.

        Are you absolutely sure th cam is timed correctly? Did you actually degree the cam or just line up the dots?

        I only ask for clarification and to understand. I still say something is hinky there. A piston .040 in the hole, a flat top at that and a relatively small cam and your hitting the exhaust valve. Wierd.
         
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        • schwinger

          schwinger 1972 Dodge Dart Swinger

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          I got confused, thought you were asking about how I got the measurement for lift but I did the clay thing, put the head on the block, put the rocker arms on the cylinder I was checking clearence for, rotated the engine while looking at the exhaust valve opening via looking at the rocker arm opening the valve and the engine stop rotating so I assumed it hit the exhaust valve so rotated the other way for the intake to open and felt a very slight stop while rotating the engine, did kept going to where the exhaust was starting to open and when it got close to high lift it stopped against assumed the exhaust valve is hitting. Took the head off and clay was smashed to where I couldn’t read it and I did mention I didn’t degree the cam but advanced it 4 degree advanced on the crank
           
          Last edited: Sep 25, 2019
        • RustyRatRod

          RustyRatRod 30 Degrees Outta Whack

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          I don't believe it either. With only .490 lift, the duration has to be such that he'd never have to worry about it.

          Cause we all know the lift is almost a moot point. It's not how much lift, but when and how long that lift occurs.......the duration that matters.
           
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          • RustyRatRod

            RustyRatRod 30 Degrees Outta Whack

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            Hang on now. You have a 5.2 MAGNUM engine? With flat tops with NO valve reliefs? There is your problem. As far as I know, no one makes pistons for the Magnum engine with no valve reliefs, so that means you have LA pistons in that engine I am willing to bet. Why does that matter? The Magnum block has a shorter deck height, so the Magnum pistons have a shorter compression distance. I bet you dollars to doughnuts you have LA flat tops in a Magnum block. The LA pistons have a longer compression height which will push the piston further up in the bore. Couple that with the Magnum's shorter dech height and you got problems.
             
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            • Blackhatguy

              Blackhatguy Well-Known Member

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              ∆∆this∆∆

              Id even think about it, but I ran into the same problem building this Magnum 5.9! I had to mic absolutely everything and do a good deal of machine work to get what I got to work the way I wanted. Definitely try to find some numbers on that piston, because if they are la Pistons somebody made a boo-boo. If they are not la Pistons, start looking at the cam degree, because as they said it's not to lift alone but the duration and timing that allows valves to hit. I have stock Magnum 5.9 dished Pistons at @ .010 deck, .028 head gaskets, heads were shaved .031. got .535/222 on the intake and .550/224 on the exhaust with 1.98 and 1.60 valves. Nothing hits right now, but it would if I retard the cam more than 5°
               
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              • schwinger

                schwinger 1972 Dodge Dart Swinger

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                Found the numbers on top of the piston. H814CP Which is Speed pro hypereutectic pistons. Looked it up and its for a magnum engine 1992 to 99 so i believe the cam is whats causing the problem. I frkn missplaced the cam card too when i moved into my new house so im gonna have a long day looking for that. This blows, should of degreed the cam but got to much in a rush for that trip. It ran fine all the way up there too but i do want to correct this problem so i dont have any future problems.
                 
              • Blackhatguy

                Blackhatguy Well-Known Member

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                That's a good start though, now that we've eliminated the pistons we just need the numbers off the cam and see how much those heads are shaved down.
                 
              • yellow rose

                yellow rose Doctor of Thinkology.

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                I'm glad you posted all this. There are many on here who emphasize how important it is to degree the cam. Every single time. Like many others who done this crap for awhile, have seen cams be 6, 8 or more degrees off. Once you get the hang of it, degreeing a cam is very easy. Some guys make it way harder, using a positive stop to find TDC, but I can do it quicker and just as accurate using my dial indicator and degree wheel.

                Please update this as you go. This will help encourage (I hope it will) guys who read this thread to degree the cam. It shouldn't be an option with any build.
                 
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                • yellow rose

                  yellow rose Doctor of Thinkology.

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                  BTW, if you are 100% sure that the cam is ground on a 108 LSA you can install it on a 104 ICL and be close. Only if you are sure.

                  Whose cam is it.
                   
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