Finally got to see Darin's car

[bob_amos]

Darin dropped by the shop today and the car is beautiful. The last time he dropped in it was the old worn out yellow. I was so surprised that I was speechless... The interior is great too. He's done a bang up job on the floors. They are some of the cleanest I have seen in a vintage car. That Holley carb change sure seems to have been a good choice. It runs smooth as silk and the whistle. Just one fun accessory... Thanks for dropping in Darin. It's always a pleasure seeing the cars from the guys here.

[47heaven]

Darin dropped by the shop today and the car is beautiful. The last time he dropped in it was the old worn out yellow. I was so surprised that I was speechless... The interior is great too. He's done a bang up job on the floors. They are some of the cleanest I have seen in a vintage car. That Holley carb change sure seems to have been a good choice. It runs smooth as silk and the whistle. Just one fun accessory... Thanks for dropping in Darin. It's always a pleasure seeing the cars from the guys here.

It was good seeing you too, Bob. Remember I pointed out to you one of the freeze plugs that looked like it was leaking? Well, after I left your place, I decided to take a spin to Hesperia and see a girl I know. The car seemed to be doing okay when I started up Cajon Pass, driving on the old Route 66 down below the 15 freeway. As I got pass the 138, the engine was bogging down in 3rd/overdrive, so I pulled over, stopped, pulled the O/D cable to disengage it and started back out (Mind you, this is where that steep part of the climb starts). It seemed to be taking off pretty well and also had a little more power, but the engine was really racing in 3rd at 50mph. I got about two miles and started smelling anti-freeze. I looked at my temp gauge and it was at about 170. So, I pulled over off the freeway at a turnout and then the gauge started to move up quickly so I shut off the engine. Got out and opened the hood and there was steam coming out from the bottom side of the engine. Yep! The freeze plug that was in question had popped out. After saying a few unmentionables, I started walking to the call box to call AAA because I didn't have my cell phone on me. As I was walking to the call box, a semi pulled over and it turned out to be a former student of mine from about 10 years back. He let me use his cell phone to call a tow truck and then we chatted and I showed him the car while I waited. Within 25 minutes, the the flatbed was there and probably one of the best tow truck drivers I had ever delt with. This guy had total respect for the car and went to great lengths to make sure he didn't scratch any of the chrome by wrapping the chains with rags and duct tape and raising it on to the flatbed carefully. When we got to the mechanic, I gave him a $20 tip for taking extra care.

When John, the mechanic, saw me drive ride up in the tow truck with the car on the back, he hung his head. He felt so bad that he reimbursed me for the tip I gave the driver. He said that he couldn't understand why they were popping out because the cooling system isn't pressurized. I remembered that I have a 9 lb pressure radiator cap on there and was curious if that caused pressure. He said that it could be, but he doubted it. Nonetheless, he will look into it.

Anyway, the car is back in shop and John is looking for better freeze plugs...the kind that you can tighten and they expand. I think the one the popped out was steel or brass. Apart from the freeze plugs popping out, the car runs and handles beautifully like you said.

[Norm's Coupe]

Darin,

Sorry to hear about the freeze plug blowing like that. As far as the radiator cap being a 9 lb. pressurized cap, that makes no difference. It still won't hold pressure because of the overflow tube on the radiator. I've always had a 7 lb. cap on mine simply because it was there when I bought the car.

[47heaven]

Darin' date='

Sorry to hear about the freeze plug blowing like that. As far as the radiator cap being a 9 lb. pressurized cap, that makes no difference. It still won't hold pressure because of the overflow tube on the radiator. I've always had a 7 lb. cap on mine simply because it was there when I bought the car.[/quote']

What is the best way to keep those plugs in? Are the ones that can be tightened in the middle and expand the end to that problem? What mainly causes them to pop out like that? Was it the fact that the engine was reving too high and that caused pressure within the block?

Is there any troubleshooting info on freeze plugs on the main site?

[Plymouthy Adams]

sometimes these are very hard to dimple especially if you are trying to install them with the engine in place and the inner fender panels still on..there is not much room to sling a hammer..these disc have a slight dome that faces outward on installation..then when whacked they dimple..the dimple then increases the overal diameter of the disc locking and sealing to the block..also recommend a sealant on installation..say Permatex non-drying(type 2?) The overall experience is a PITA

[Don Coatney]

Like Norm I am bull headed. I still think your problem is excess pressure in the system due to no working thermostat by-pass system. You appear to have an internal by-pass but my guess is the wrong backing plate is on your water pump.

On another note where is your air cleaner support bracket? This bracket also has a clip to hold the throttle return spring. It appears your return spring is stuck in the end of your spark plug wire loom.

[Young Ed]

Darin has a later engine so he probably didn't end up with that return spring bracket. I might have an extra one around but you'd have to have the proper air cleaner to make it look normal.

Very curious issue about possibly not having any thermostat bypass. From the description of Darins drive it sounds like when his freeze plug blew he had been driving for a while and his engine should have been warmed up. So the thermostat would have been open and relieving the pressure?

[Norm's Coupe]

Darin,

Here's another possibility as to why you are blowing plugs. As Tim mentioned, the plugs expand in the opening when hit with a hammer. It appears that your plugs are still bowed out a lot. They are only slightly expanded with that small punch indentation, so they are not that tight to begin with. If you take a look at the one just below engine serial number you'll see that. Now, take look at that plug in my engine. You don't see any small indentation in the center in mine in the center. The whole plug is indented. That's because we didn't us a small punch, we hit them with a ball peen hammer to expand them. In mine it's even hard to see that same plug in the picture. There is no dome left on any of my plugs. The whole dome has been forced to face into the engine.

[bob_amos]

Darin, Gee, sorry to hear that you had trouble with that core plug. The reason it blew out was because it was not installed tightly. As you recall, it was already leaking around the edges so its tighness was already in question. It is located in a real tough place to collapse properly and since yours were steel, or at least it looked to be steel, it is that much harded to collapse and seal. I actually rigged up a long bar/punch to install mine. That gave me room to really hit it hard. Remember how I told you that I used steel in mine and lost that very same plug? So, I change all of them to brass, which is what I would have liked in the first place. The parts house just had steel and I figured that they would work. But they did not. The rubber expandable plug is best used as an emergancy item. They tend to break down the rubber and slide out in the end so avoid them. I carry one for emergancies just in case. Have the guy install brass and use a sealer like Permatex or Indian Head sealer to aid in sealing. Be sure to collapse the dome out of the new plug. And be sure the surface is completely clean. A properly installed plug should hold under the small pressures that our vehicles put on those plugs. Good luck and let me know how it comes out.

[kencombs]

I also noticed the small indent in the plug. And, most likely that is the problem, most of the dome should be reversed to lock these in.

Radiator pressure should have very little to do with it. The radiator itself should fail long before cooling system pressure would push a core plug out.

After all, newer cars run very high pressures and use essentially the same plugs.

And centrifugal pumps, like our water pumps, just aren't capable of creating high pressures. They move a lot of water but at very low pressures. restrict the output to any large degree and they just spin without any result.

[Don Coatney]

I am not talking about radiator pressure. I am talking about internal pressure in the block due to thermal expansion. If there is no working thermostat by-pass the water (coolant) in the block has no place to go once it heats up. The water pump is trying to push more water into the block building what ever pressure the pump can produce. As the water in the block heats up it expands. This could cause the internal pressure in the block to elevate above what the water pump is capable of producing and possibly blow an expansion plug.

[david lazarus]

I have never had or seen a frost plug pop out (rust out ...yes). My recollection of the install as well as using a gasket sealer of some sort was that the frost plug was a very snug fit to start with, needed to be tapped around the edge to get it into position before the final "whak" toget a good wide area of deformation. I would be watching/observing the re-install of the new plug with close interest.

At this point I admit to ignorance of the possible water pressure problem within the block.

To test the tightness of the plug perhaps a small amount of superglue to the plug and another tool to see if a slight tug dislodges it. Can't think why but maybe the frost plug hole is not perfectly round.

[kencombs]

I understand Don, but don't forget the thermostat blocks the outlet and the pump 'blocks' the inlet. So the pressure shouldn't be able to exceed that the pump is capable of producing or the fluid will just 'backflow' against pump pressure. the two aren't and can't be additive.

Still think the mechanical lock due to inadequate dome upset is the real problem. Or maybe some Chinese plugs are slightly undersized????

I would measure with accurate calipers, the replacements and compare to the original spec.

[47heaven]

Hey guys...thanks for troubleshooting this problem for me. I sent this thread onto him to read so he can get a better idea, too. I have total faith in him because he is a good mechanic; as he is just as confused as some of you are on this freeze plug issue.

The freeze plugs that came with the distibution tube a a kit came from Robert's. I recall that the plugs were steel colored. I don't know if they were steel or aluminum. The two that have popped out so far have been the two on the bottom. The top ones haven't shown signs of any leakage.

Again, the engine is a D30 with a P26 head and crank. Since the engine that was in there was a P26 when I bought it, the air cleaner was already a filter type from 1955, so I don't know if the brace will go with it.

Anyway, we'll see what happens now, but I know the feedback here will help him solve the issue. Thanks, again!

[Normspeed]

See Darin, that's whatcha get for not bringing along kindly old uncle Norm when ya go visitin' the gals. Think of the havoc we would have wreaked with DUAL wolf whistles.

I think the brass plugs might expand better. I have some of the steel ones too, and they seem thicker and much harder to expand. Everyone has their favorite sealers. For this type of job I like the red Permatex in the photo. It cures up really tough after 24 hours. If your mechanic cleans the area well, adds some sealer, and punches the plugs real good, you should be good to go.

It sounds like the car was running a bit cooler with the timing reset, until the plug let loose. I agree with Ed J, after that long of a drive up the pass, the thermostat should be fully open so I can't see that the bypass would be in play. However, if you continue to have hot running problems I'd have the mechanic (or you and me) pull the pump and verify that the gasket and rear plate on the pump are correct.

[Don Coatney]

Pictured is the sealent I use. A while back I measured both the steel and brass plugs. The OD was the same on both as pictured.

[Norm's Coupe]

We used steel plugs in my engine too. Don't remember what kind of sealant we used. We were assembling the engine at my friends automotive shop after hours. Was warmer there than in my garage. Whatever he had laying around at the shop, is what we used. The steel plugs should not pop out like that though, if installed correctly.

[Plymouthy Adams]

I was going to put in an original steel plug...cound that trying to dimple the animal while the engine was in place and inner fenders etc etc..just did not make for a good happy feeling..

I bought instead the rubber insert...now as we most know...these animals are very thick..thick enough to hit the inner jacket on our blocks..solution..shorter bolt and cut the rubber ..can actually make two this way..insert one and place the other half for a back up down the road..or buy another washer the correct size and obtain second shorter bolt..

[kencombs]

I see that your sample measure .0015 over the nominal 1 5/8" hole standard. I wondered if you (or anyone) had measured one after dimpling it? Or measured the actual hole size to see if maybe blocks weren't all identical, or if corrosion could oversize the cast?

I will likely be building a replacement for my pickup engine in the next few months and am trying to get prepared. It's been a long time since I worked on a Mopar flattie!

If anyone has a 251 or 265 core layin' around I might be in the market.