--Judging from what I see looking at the plugs, they are all the original 'dish' style (like my 57) and not the 'cup' style. I have never seen or used the ones with the bolt style like the Hot Heads units that Mr. Grady sent along.So, my next question is, if the original was not cup style, will a cup style or bolt in style work in the dish style block opening, or is there something different about how the block was cast in order to accept one style plug over another?I haven't been to the Hot Heads site in a while, but I always thought of them for Gen 1 Hemi stuff and not later model wedge stuff. I'll check this afternoon while hunkering down indoors here on a 100 degree day here in TX.On Sun, Aug 23, 2026 at 9:35 AM henry.schleimer via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:--I once popped a brass core plug out of the head of the 318 I had recently rebuilt. Luckily, I was only two miles from home, so I got it back with steam trailing after me. After a bit of rewinding in my mind, I remembered that for this particular plug, I had first punched it in slightly crooked and then straightened it with subsequent hits. I realised then that this was a bad idea and should have got a new one to try again.
Therefore, if you can’t get a straight hit on a plug with the engine in place, I strongly suggest you try one of the alternative plugs mentioned below that don’t have to be hit.
Cheers
Henry
From: chrysler-300-club-international@xxxxxxxxxxxxxxxx <chrysler-300-club-international@xxxxxxxxxxxxxxxx> On Behalf Of James Nicolaus
Sent: Sunday, 23 August 2026 10:59 AM
To: John Grady <jkg@xxxxxxxxxxxxxxxxx>
Cc: dave mason <forwardlook300@xxxxxxxxx>; John Nowosacki <jsnowosacki@xxxxxxxxx>; Club <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: Re: {Chrysler 300} freeze plugs for 61 413
About 40 years ago, I put in a Dorman "expansion plug quick seal copper" {not the rubber type} to replace a failed disc-type plug on a '62 361. Installed with a dab of Permatex "steak sauce" around the edges. It's still there today and not leaking. Still available in various sizes according to their website. It too was behind the motor mount and impossible to replace without performing a Houdini act. I think the big blocks switched over to cup type about the same time as 6-bolt valve covers.
On Sat, Aug 22, 2026 at 11:55 AM John Grady <jkg@xxxxxxxxxxxxxxxxx> wrote:
just me , but weeping at edges not uncommon ; depends if wet now after a drive . old weeping looks bad but may have been /is stable for years . Might be scratch or junk in cup bore etc
I have a car , 60 Buick actually, flipped I out 30 years ago when I saw weeping/ rust right after purchase .
Unbelievable amount of work to change, could not see how I could drive plug in so punted . Was summer driver for two years 20 years ago . Never added coolant after initial checkout , plug and rust still there
But if you see evidence of leakage inside cup ,at cup fold plug is going/ gone , I have see that in ones removed. .. usually due to lack of changing coolant / rust prevention fades .
I suddenly feel guilty
Another aspect , I have had two disasters over core plugs both on disc type used in hemi (and I think early B block ?) Both times blew out in first 100 miles on new engine far from home . One on the block , one time small one in head casting.
Today's mechanics/ machine shops have no idea at all how hard to hit them , cannot be done right imho in car . The hit is hard , dead center with BIG ball peen hammer , makes noticeable depression .( look at stock one) Many put sealant , may be smart but sealant will not hold plug in ( maybe old style permatex might help ?)
Hot heads knows all this, they make a really cool SS and aluminum one I think has O ring . It is held on by toggle bolt arrangement , not a tight fit ,no hitting . Toggle bar spans hole inside block , bolt screws into it
Love em, pricey , worth every cent vs sudden loss of all coolant from rebuilt engine, at 200 degrees (for first time) brand new . Happens when hot, (of course,) because of pressure rise
But also ?the answer to change in car ?? if B same size , might help if it needs change .
Maybe routinely after a new engine install put 18 psi on cooling system. I forget , this post reminds me
Another approach if weeping is so called radiator sealant . No it does not " plug radiator" as armchair experts think . Very small particles seal up tiny spaces . Personally I 'd just touch up with antifreeze , see how much you add . A cup a year is noise?
vs a new one put in wrong by a lame attempt in car .
If cup type , yes brass !
ymmv
J
On Aug 22, 2026, at 11:55 AM, 'dave mason' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:
Hi John,
You may already know this - These are 1-5/8” I believe and I would definitely use brass. I am not sure when Chrysler did the changeover from disc type to cup type. Both are available but the cup type are common, disc less so…
D&K
Sent from my iPhone
On Aug 22, 2026, at 11:38, John Nowosacki <jsnowosacki@xxxxxxxxx> wrote:
Under the car yesterday double checking fuel pump installation from last thread (car still runs fine, no fuel leaks), when I looked a little further up and back from the fuel pump and noticed the forward most freeze plug looking a little nasty and having a wee bit of wetness below it. I guess eventually a 65 year old freeze plug on a never rebuilt engine could eventually start to weep.
Since I've never needed freeze plugs on any old car before (not even my 55 or 57), thought I'd ask if anyone in the group has done their freeze plugs on a 413 lately and had any recommendations for a brand of plugs. I assume I'd want to go with brass over steel to avoid rust problems in the future? Again, never done them before, not sure I'll be the one to do the job, but looking for advice on type/brand to use. Maybe also if there's anything I can/should do or avoid doing in the meantime while I look for plugs and a shop willing to install them? Of course, that forward most plug is close to being obscured by the motor mount, so hopefully that mount doesn't have to be removed to get the job done. As always, any advice appreciated.
--
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