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Hemi core (freeze) plugs

Discussion in 'The Hokey Ass Message Board' started by TDWZ28, Mar 21, 2011.

  1. TDWZ28
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    TDWZ28 Member

  2. 345 DeSoto
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    345 DeSoto Member

    For as much as you're going to run the engine, go to NAPA and get the regular steel ones.
  3. Mr48chev
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    Mr48chev
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    Or a set of brass ones intended for marine applications.

    They aren't that hard to install correctly and I've never had problems with stock style freeze plugs in any engine I have worked on. Put a bit of #2 Permatex in the hole or around the edge of the plug and drive it in using a driver or something the correct size for a driver.
  4. deuce354
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    deuce354 Member

    I used brass ones from NAPA, a slight coating of JB weld on the plug. Hold the round end of a ball peen hammer on the center of the plug, Hit the flat end of the hammer with another hammer to make a dimple in the plug. This expands the plug. Did mine 12 years ago Successfully
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  5. deuce354
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    deuce354 Member

    I forgot to mention these are disk type plugs , NOT cup type plugs
  6. George
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    George Member

    What he said!
  7. bangngears
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    bangngears Member

    Stock Hemi freeze plugs suck,they were not designed very well,especially when you have a Chevy water pump on the Hemi.I would put mechanical freeze plugs in and feel comfortable they will not fail out on the road. Been there and was not fun,luckily i was close to home.
  8. 73RR
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    73RR Member


    WTF? Do you actually believe that the water pump is responsible for the system pressure?

    The disc style 'sucks' only if you don't know how to install them.

    .
  9. Dreddybear
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    Dreddybear Member

    I've had success with indian head around the plug.
  10. speedyb
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    socal

    speedyb Member

    Funny, I just pulled a 392 out of a 57 imperial and It had all of the original soft plugs still in place and leak free, Install the new ones correctly w/a little dab of leak lock around the edge.
  11. scootermcrad
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    scootermcrad
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    Standard disc type... Nothing fancy. Installed correctly and they should last forever.

    [​IMG]

    Clean up the ID of the plug bore with a fine grit flap wheel or sanding drum. Don't take too much off or the disc won't over seat.

    [​IMG]

    Apply sealer or JB Weld around the bore.

    [​IMG]

    I use a piece of 1" diameter solid round stock and a big ass hammer to set it. The way mentioned above will work just as well. Needs a couple good solid whacks! Then wipe off any extra sealer after the install. If you use something silicone based, know that paint will not stick to it. JB Weld is a good way to go.

    [​IMG]

    [​IMG]
  12. TDWZ28
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    TDWZ28 Member

    Thanks for the replies everyone. I put a stock steel one back in it. I used the aviation perma-tex sealer and a piece of 1" round stock with a rounded end on it for a punch. Warmed the engine up and it is holding.


    Nice pictures scootermcrad! I appreciate it.
  13. tig master
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    tig master Member

    Perma tex is the answer

    Tig
  14. Ebbsspeed
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    Ebbsspeed
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    There are actually two sources of cooling system pressure in a running engine. The one we all are familiar with is the pressure from heated coolant expanding, and trying to turn into steam. The second source of pressure (in the engine not the radiator) is the spinning water pump. It is pushing coolant through a system that has restrictions, ie, the thermostat, and when the thermostat is closed the water pump does create some pressure. If it didn't, the coolant wouldn't circulate.

    Proof? I witnessed it on a friends car last summer. Freshly rebuilt 327 Chevrolet, with plenty of power-enhancing internals and bolt-ons. He had about 500 miles on the engine, and decided to give it a little extra hard push to see what it would do. He wound it up tight leaving a stoplight, and the impeller cover gasket on the back of the water pump blew out. Where did that pressure come from?
  15. 73RR
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    73RR Member


    The pressure he saw was localized, the same kind of 'pressure' that builds when a pump cavitates. If he/you were to measure the 'pressure' increase downstream of the impeller you could also measure a similar 'pressure' decrease upstream. This is how pumps create 'lift', by producing a low pressure zone that the available fluid wants to fill. It is a closed system, you cannot just 'make' 17lbs of system pressure without an external force (heat). Yes, if you spin the pump long enough and hard enough you will create some heat but the impeller will be dead long before you build 17lbs pressure.

    .
  16. ajmopar
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    ajmopar Member

    Probably his leaking head gaskets.
  17. Ebbsspeed
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    Ebbsspeed
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    If you read your response carefully, you will see that we are saying the same thing. There is system pressure from the heated coolant, and there is localized pressure between the water pump and the thermostat. Compared to atmospheric pressure, there can be higher pressures at the "high" side of the pump than the pressure in the radiator.

    Pretty good head gasket trick, in that they resealed themselves. We thought it might have been a head gasket failure that did it, but a compression test showed otherwise.
    Last edited: Mar 23, 2011
  18. bangngears
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    bangngears Member

    In response to 77RR,as a matter of fact i do blame the Chevy water pump.Both times when i blew out a stock Hemi freeze plug it was because of a WOT blast down the boulevard.Now you will never convince me a freeze plug installed by exspanding it with a blow from a hammer on a dowel pin is as good as a mechanical freeze plug.Most of the racers back in the day had mechanical freeze plugs because stockers could not be trusted.The same freeze plug on 2 differant engines came out,middle plug on passenger side.If it works for you thats fine.Hope you dont have to learn the hard way.I have peace of mind with my mechanical freeze plugs.
    Last edited: Jul 4, 2011
  19. willys36
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    willys36 Member

    I drove my Willys for the first time in about a year this morning and blew the middle plug on the dirver's side for the third time in my 331 block. The Hemi hammer-in plugs are not a very good design, ast least for a block that has 60 years on it. Will hammer in another one but use epoxy this time. And believe me the water pump can add signficant pressure in the block behind even an open thermostat. First time I blew the plug was when I was cruising at temp and hit the throttle; BOOM steam everywhere!!
  20. racer-x
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    racer-x Member

    for a stock application if installed correctly the stockers should be fine. problems can arise when more power is built in the engine. the hot heads plugs are far superior to stockers. i had my car on the chassis dyno and blew out three stockers. if i was on the track and that happened i would have totaled the car. since i have installed the hot heads plugs i have had no more problems. the block only needs to flex a little bit to release the tension on the plug. mopar circle track racers used to drill and tap the block then bolt a metal strap across the plugs to hold them in. core shift,rust and flex all can release a stock plug. they are cheap insurance as far as im conserned. its just not worth the risk. why go cheap now on your build? how much money do you have in your car right now where you cant aford the best parts? if there was never a problem with the stock plugs no one would have spent the time to invent a better plug.
  21. drumyn29
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    drumyn29 Member

    what he said! I heard about boring the inner lip off and supposedly ford or sbc plugs work but I used the expensive yet crappy hot heads with lots of j-b weld AND silicone. Terrible design.
  22. TDWZ28
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    TDWZ28 Member

    A few days after I installed the factory ones, a couple of them started to drip. I bought a set of the HH ones and installed them. No leaks at all, and I've hammered this old Hemi pretty good a few times.
  23. stegto
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    Italy

    stegto Member

    After months I am still here with problems with my 270 Red Ram leaking from freeze plugs. I was not able to find the stock ones (Dorman, Rockauto, Kanter who sold me wrong ones), so I decided to buy copper plugs from Hot Hemi Heads: bad idea, they not stay in place and leaks more then before... Anyone knows a place where I can find the original ones?
    Thanks in advance.
  24. TDWZ28
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    TDWZ28 Member

    See the link to the HH ones in my first post. They work. No leaks at all after I installed them. Not cheap, but worth the money in no aggrevation.
  25. bangngears
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    bangngears Member

    Thank you Willys 36 for some support on this issue.Both hemis i referred to in my 2 experieces,one was supercharged and luckily happened in the garage when i winged it up,the second was from a wot launch on a back road 20 miles from home.I will say again stock hemi freeze plugs suck and or not to be trusted,go with mechanical and any worries are over.
  26. sunbeam
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    sunbeam Member

    When was the last time you saw a recall for blown out core plugs? Must have been the installation I use little KD block sealer on them.
  27. ago
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    ago Member

    On my Hemi I used the bypass on top of the BB water pump and plumbed it into the crossover to equalize the pressure.



    Ago
  28. George
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    George Member

    or J B Weld...
  29. TR Waters
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    TR Waters Member
    1. Early Hemi Tech

    I sell alot of the stock type, and dont hear of any problems. I do have written instructions that say to use a good sealer, and NOT silicone.
    On the other side of that, I have seen some blocks where the inner lip of the hole was very rusted. In that case I would clean the hole spotless, apply some JB around the hole, install and expand the plug, them use a narrow bead of JB around the outer edge where the plug meets the block. Of course, the above is useless if you dont take the time to clean the area.
  30. Hot Rod Willys
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    Hot Rod Willys Member

    I found and read this thread after I had installed my blown 392 Hemi in my 1941 steel Willys, my motor has the factory type freeze plugs in it. I went to a Chrysler engine guy to build my motor and dyno it because I wanted to be sure he did everything right. He has built early Hemis for 40 years. I got the car running last week and today I took it for its first drive. Before today it had 4 pulls on the dyno and about 45 mins. of garage tuning, I went down the road easy as the whole car was a frame up build and everything was new. I went into an industrial park and pushed the car about 1/4 to 1/2 throttle and about 2 sec. after launch I blew the drivers side center freeze plug, what a mess! I had to call a friend and tow the car home. I am going to call Hot Heads tomorrow and ask whats best to solve this issue. My motor has 650 hp and runs a chevy electric water pump with a 5/8 restrictor plate instead of a thermostat. Im sure the builder installed the plugs correct so there is something going on with blown 392's and stock plugs and chevy water pumps. I will post what Bob Walker tells me. Here is a link to me warming the car up in the garage before driving.
    Mr. Gassers 1941 Willys - YouTube

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