7.3 cooling mod

Discussion in '6.9L IH & 7.3L IDI Diesels' started by IDIBRONCO, Jan 6, 2018.

  1. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I have no pictures because I did this to mine a couple of months ago. This is also only my experience and I've only done this once. Explanation: this mod doesn't actually increase the cooling of a 7.3 engine. This is a preventative procedure. With the 6.9 block and heads, as you're looking at the mating surface (the deck on the block and the bottom of the heads) from the side of the engine as if it's out of the truck on a stand, at the bottom front and rear of the surface, there is a coolant port that has been blocked off on the 7.3. The 6.9 head gaskets have a roughly triangle shaped insert that you have to put in place in these locations. The insert appears, to me, to be made of thin steel with a rubber coating over it. there is a small hole in the insert that allows some coolant to flow through the insert. The reason for the blocked off ports on the 7.3 seems to be for emissions purposes (that's the best guess of several knowledgeable members on here). This causes some heat to be held in these spots on the 7.3. My opinion is that this is also the cause of the "chuffing" with the 7.3 exhaust valves. They aren't cooled as well and tend to wear out faster than those on the 6.9s. Under normal, unloaded, operation, this is not a problem, unless it actually does contribute to the accelerated exhaust valve guide wear. When these blocked off ports become a problem is when you are putting a lot of heat into the cooling system. My example would be when you're towing heavy in the summertime while running the A/C, while your turbo is also boosting high and putting that much more heat into the cooling system. What happens under this type of situation is that your coolant can actually start to boil inside your engine. Steam has more pressure than hot coolant does and this can cause your heads to lift slightly off of the block. just a few thousandths of an inch isn't much, but it's enough for the steam inside your engine to escape to the outside, causing your head gasket to "blow". By removing the plugs in the 7.3 block and heads and then using 6.9 head gaskets, you get the same coolant flow as the 6.9 does thus greatly reducing, if not completely eliminating, the head lift problem. I thought about using 7.3 head gaskets until I realized that the 6.9 inserts appear to be steel with a rubber coating. 7.3 head gaskets may work if you make holes for your coolant to flow through them, but I wouldn't recommend it. I figure there was a reason for International to use the inserts instead of making holes in the gaskets. Now for my experience doing this. I tried drilling a 1/4" hole in one of my block plugs. It didn't work very well because the plug seemed to be very hard (I'm thinking stainless steel like the core plugs in the outside of our blocks). I then tried to punch a divot in the plug with a center punch and the I punched whole plug through the hole in the block into the cooling jackets. Then I took a small chisel and carefully punched it into the outside edge of the next plug. By doing this, the plug actually rotated in the hole and was sticking up sideways. I could then take a pair of Vise Grips and carefully, with a rag underneath them for a cushion, clamp them onto the lip of the plug and lever it up, out of the hole. This was MUCH faster than trying to drill a hole in the rest of the plugs. The plugs in the heads came out the same way. As an added bonus, at the time I ordered, I bought 6.9 head gaskets for about 1/2 the price of 7.3 head gaskets and they were all Fel-Pro which are .010 thicker than Victor Reinz. I'm sorry that this was so long. I tried to be very detailed for new members who don't know a lot about their engines yet. This was my experience. I'd like to hear opinions
    and other experiences. I did this because Thewespaul asked for it and others ask for it too.
     
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  2. Thewespaul

    Thewespaul Supporting Member Supporting Member

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    Thanks for doing this @IDIBRONCO! Always great to preserve stuff like this on the forum, Ill try to snag some pictures of spare blocks, heads and head gaskets so people can see exactly what you're referring to.
     
  3. icanfixall

    icanfixall Official GMM hand model

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    Really an interesting "idea". Now run it like you stole it. Report back the good and the bad no matter what happens.
     
  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Thanks Thewespaul. I hope you liked it. I hope it helps others understand this. I tried to keep it as basic as I could. I'm sure your pictures will help too. Do you have any experience or opinions on this write up?
     
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  5. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    icanfixall, I will. I'm at the point right now, where after getting my block back from being hot tanked, cylinders honed, and new cam bearings installed, I discovered that three of the good stainless "freeze plugs" have been replaced. Since I don't have the tool or the knowledge, and I don't know of anyone close to me who does, I'm going with the Boss 429 style. That's all the farther I've made it as of right now. The whole thing is on hold until I ca start at the beginning.
     
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  6. Macrobb

    Macrobb Full Access Member

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    If you are building a new motor for turbo use and have new exhaust guides fitted or oversize stem valves installed(good clearances), I'd recommend deleting the valve stem seals.

    From my own experience, it won't create smoke or oil usage(remember, with the engine running you have /positive/ pressure on both the intake and exhaust valves, pushing oil up and away from the valve head) and should make the guides last longer.
     
  7. TahoeTom

    TahoeTom Supporting Member Supporting Member

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    Last edited: Jan 9, 2018
  8. Thewespaul

    Thewespaul Supporting Member Supporting Member

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    Here are some pictures for y’all, I circled some of the plugs and their locations.
    FC018D5C-63E8-43EB-9524-F33848383AC9.jpeg 98B0B1DE-7B27-4720-BE72-F76B13DC5815.jpeg 8DC51495-E3AE-4178-8630-1FCBE929C654.jpeg DA5F11E6-FB15-4B54-9734-89396E01BF1F.jpeg
    @IDIBRONCO, I have had some experience with this and seemed to work well, only thing I have to add is I have had luck by punching a small hole in the center then heating and freezing the plug, then pulled the plug out with a pick through the small hole.
     
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  9. Nick382

    Nick382 Full Access Member

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    Too bad it's such a headache to get to. Seems worthwhile, and costs very little.


    Sent from my iPhone using Tapatalk
     
  10. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    It's easy if you have your heads off for any reason. Otherwise, I wouldn't worry about it. It seems to be only under extreme conditions.
     
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  11. Runningaford

    Runningaford Registered User

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    Awesome idea; I'll get on the tear down in the morning! hahahaha..... Actually a great idea should I ever have it out, and apart.
     
  12. david85

    david85 Full Access Member

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    I did not know the felpro gaskets were thicker. Good to know.
     
  13. DrCharles

    DrCharles Full Access Member

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    How much does that added thickness reduce the compression ratio? I'm not planning to turbo my 7.3 in the foreseeable future, and would like it to keep starting in cold weather...
     
  14. Thewespaul

    Thewespaul Supporting Member Supporting Member

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    It won’t make a noticeable difference
     
  15. Macrobb

    Macrobb Full Access Member

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    Good glow plugs and starter is what really matters when starting cold; a little bit of compression loss won't make that much difference.
    Now... a /lot/ will make more of a difference; I once tested out a set of "decompression" gaskets, which were literally 3 layers of steel with 2 layers of gasket between them... so over twice as thick as stock.
    I had to do some messing with the timing and advance to make it work out right, it definitely needed more advance to actually fire decently.
    And I do *not* recommend doing decompression of any sort(.010" isn't a big deal, .030+ is), to an IDI - they just don't like it.

    The thing about lower-compression IDIs is that they won't fire on Ether. It takes a lot of cranking and a lot of ether to get them to start at all, so you had better keep your glow plugs in good condition.

    I found that with both the 7.3 with decompression gaskets and a '83 6.9, which has 20.5:1 compression stock. With glow plugs, they fire right up. Without glow plugs and with Ether, they don't want to.

    With a higher-compression motor, ether will actually fire cold, it's possible to etherlock it even when it's below freezing out.

    I would not have expected such a difference, but I've experienced it personally.
     

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