Freeze plug in GN-1 came out, twice.

[Nashty]

At the top end of the track my drivers side front freeze plug came out, drained all the water out of the motor under my car. (Believe it or not, the car never got out of shape.)

I have no water in the oil and when driving it normally, there is not any water in the overflow but it does have a tendancy to push out a small amount and then once it's lowered its water level a bit, it doesn't do that anymore. Car doesn't run hot at all. I have a S1 block with the additional head studs. My biggest hunches are that I'm still lifting a head and doing the water push OR a leaking intake gasket. I had one stripped bolt in the head for the intake manifold but I put it together anyway (call me lazy but this was like 2 days before Nats). Could the intake gasket be the source? I do have a fair amount of blowby too but only after running it hard.

I have lockwire head gaskets and ARP studs.

When I run 30# of boost alone, it is fine. This only happens when I run the N2O which is only a 50 shot. The log files show everything is working just fine with the A/F. I also run 19º or timing with the N2O.

Any ideas?

Roger

BTW, that last run was:
1.386 - 60'
5.864 - 1/8 ET
123.15 - 1/8 mph
9.39 - 1/4 ET
123.33 - MPH

It let go well before the end of the run. Check out the 1/8 vs. 1/4 MPH. I was on a tear that pass.

 

[S2V6RACER]

The head(s) are cracked. Ask Chris Lyons about his experience with this problem about 1 year ago to the date.

 

[Nashty]

Cracked? Wouldn't have guessed that, could you elaborate?

 

[Mac in SD]

Freeze plug in the end of the head or side of the block? Either way, it's usually a sign of cracking. Champion heads were like Rice Krispies a coup;e of years ago, before they modified the castings.

 

[S2V6RACER]

Again, this happened to Lyons down at BPG last year. He ended up finding the heads all cracked up. He would blow the plugs at the last part of the 1/4.

From a forensic point of view, I find it amazing that the coolant pressure did not pop the cap on the radiator first. I imagine it happens so fast, as if when the engine power level gets to a point, it flexes the head and opens up the system to cylinder pressure. I would guess the cracks are going to be in the combustion chambers.

These must be OLD GN-1 castings. The first batch that got the 14 bolt head treatment will fail in this matter from what we found out.

Let us know!!!!!!

 

[EightSecV6]

it is tough to fix a crack in the freeze plug area, you are better off the machine an aluminum plug and weld it in place along with the crack.

 

[TurboDave]

it is tough to fix a crack in the freeze plug area, you are better off the machine an aluminum plug and weld it in place along with the crack.

That's what I was thinking. Problem you run into with aluminum heads/block is that age old problem dating way back to chevy's ZL1's Aluminum and freeze plugs being different metal expand and contract at different rates.
This will usually always lead to leaks at the plugs eventually, and if you've got something helping it along like unusually high pressures in the coolant system they're going to be popped out pretty easilly.
That's the reason the TA blocks have screw in plugs everywhere.

 

[bruce]

From a forensic point of view, I find it amazing that the coolant pressure did not pop the cap on the radiator first.

The thermostat acts as a restrictor, so the block/ heads operate at a higher pressure, then what the radiator sees. Especially at the higher RPM levels.

 

[Nashty]

Again, this happened to Lyons down at BPG last year. He ended up finding the heads all cracked up. He would blow the plugs at the last part of the 1/4.

From a forensic point of view, I find it amazing that the coolant pressure did not pop the cap on the radiator first. I imagine it happens so fast, as if when the engine power level gets to a point, it flexes the head and opens up the system to cylinder pressure. I would guess the cracks are going to be in the combustion chambers.

These must be OLD GN-1 castings. The first batch that got the 14 bolt head treatment will fail in this matter from what we found out.

Let us know!!!!!!

These are old Champions. It's still sitting in the garage all put together. Are you suggesting that the combustion chamber is cracked or there is a structural crack elsewhere? It sounds like you are saying it is in the combustion chamber and Bill and Dave are suggesting the freeze plug area.

As far as the restriction goes, I'd have to add that I basically have no radiator hoses. I run tubing in place of the lines with only short silicone hose sections at the junctions.

I'm going to sit on it for a while. I've got a buddies car to fix for now. I also just heard some devasting news about a great young man killed in a TR this weekend. I'm going to do what I can to support his family.

 

[turbobuick]

I popped two of them at last years BPG NATS. These were on early casting heads and I definitely WASN'T pressurizing the cooling system. To be honest I still don't have a reason why they popped??

The heads did crack in the usual spots by the exhaust ports and studs. They didn't crack around the freeze plug. The only logical reason I could come up with is that the early castings flex so much that the freeze plug hole can actually become distorted enough to blow the plug. I've since had the heads replaced with later casting and have not had any issues what so ever. Tom was actually VERY good about helping me out. The new heads have been off since and have not shown any signs of problems like the early castings had. I still don't think a screw in casting plug is a bad idea.

 

[Reginald West]

I have not had any problems with my M&A heads leaking but I have blown the freeze plug out on the passenger side of the block. It turned out to be a crack in the block between the freeze plugs.I pinned the block and filled it up past the freeze plugs with Hard Block. I have been racing it for a year with no problems, I even drive it on the street once in a while and it does not over heat. Glad to hear you did'nt have any problems when the coolant came out.When mine let go I was at the top of the track going about 135 and it all sparyed on the rear tires.I still don't know how I missed the wall and stopped the car.Let us know what it turns out to be.


REG

 

[Mike Licht]

I had one come out in a prototype M&A head that cracked in the middle. Once it cracks it seems to pressurize the head and they blow out. My car got a little squirrley but stayed on the track. Seems ot be common when the heads crack
Mike

 

[Dominic]

I have always drilled three holes in a triangle fashion (even 2 will work) around the freeze plug boss in aluminum blocks/heads and used small screws with overlapping washers to keep the freeze plug in place in case of an event like this. Because we all know $hit happens whe you make big power!