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Riceburner

Blown welsh plug

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I asked this question in my build thread but is probably more suitable in this section. First time at the track yesterday did 1 warm up lap and almost 1 flying lap when a coolant smell wafted into the cabin, I also spun in my own fluid. Got back to pits to find a welsh plug completely missing from the front of the block on the drivers side! Is there a reason it would pop/blow out?

 

Temps were fine, oil pressure fine. I used permatex no.3 (aviation cement) when installing them.

 

I was able to repair, test and drive home and the water level has not dropped since topping up. I'd like to get to the bottom of it as I think I was very lucky not to destroy my brand new motor :'(

 

Anyone else had this before? Are the low temp stat, LD28 water pump, Kameari high pressure cap a bad combo at high revs?

 

All water pumps will cavitate if you spin them fast enough, so the idea of reducing pump speed at 7000 rpm makes some sense. The thing is that at a point beyond optimum pump speed, block water pressure drops. Dropping the speed of the pump to a point to where the cavitation is eliminated will only RAISE the coolant pressure in the block water galleries!

 

I believe that you may have had a 'faulty' welsh plug in your engine. Nothing more. Your pump, radiator cap et al are just upgrades on a standard setup, applying greater pressure on the cooling system to get more performance from it (pun intended BTW). You found your weakest link, more often its a hose and we wouldn't think too hard about that one, would we?

 

You can check your block coolant pressure by fitting a pressure guage to a fitting below your thermostat. Don't let it go too far...35 psi is where you want it to peak and stabilize. Too much coolant pressure is dangerous.

 

Restrictors are far more consistant to finding the right pressure than a thermostat. You have to deal with open/closed pressures, flow rates, block pressure and temps. For racing, restrictors are king. For a 'street' engine, go the thermostat route is my call.

 

Cheers.  :)

 

 

 

 

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Thanks for the explanation Mark, I'm actually going to try the don potter resrictor with a brand new nissan T/stat. They are quite an interesting shape, the Nissan stat is slightly offset and has a rubber seal in the centre to close the stat 100%. Very different to the generic replacements.

 

It was going real hard Peter, even if it was only for 3/4's of a lap. Hehe.

post-1489-144023621263_thumb.jpg

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You're welcome Gareth.  :)

 

Why don't you try the restrictor first, without any thermostat. The resistrictor is designed to replace the thermostat in these conditions. Using both at the same time doesn't test either component to see which one is giving you the desired results you're seeking.

 

The little taggy thing next to the main part of the thermostat acts as a tiny bypass. The thermostat cannot close off 100% of the flow with one of these thermostats. I have experimented with one and twisted it off and plugged the hole. I did this because I could feel hot water in the top radiator hose before the thermostat actually opened! Solved that problem.

 

I don't know if your engine has the external bypass line from the thermostat to the intake on the front cover like mine does. I believe there is an internal one too for those situations that require it. They allow water to flow around the block before the thermostat opens, keeping the head of water pressure at a manageable pressure and prevent cavitation that would drastically reduce coolant flow through the engine. They did this for the people who rev their engine hard on a cold engine!  :o

 

Bad luck on track day man......next time hey!

 

Cheers.  ;)

 

 

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Hi Guys,

          The late Don Potter ( D.L.Potter Engineering ) had some innovative Zed car accessories available for performance engines. A few months ago a lot of new (old) components were for sale from mamabears lair in the USA on ebay. One of the items that I purchased was the Don Potter water restrictor and the instructions stated that it was to be used with a 190 degree thermostat to make the modification effective. This was used in racing cars because apparently the engines ran better at a higher temp.

Regards

David :)

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Mark, it was just bad luck I hope. I don't have the bypass hose on mine but I have always drilled a 3mm hole through the outer ring of the tstat as recommended by Bazz from Datsport and has worked well so far. Like David says, this restrictor comes with instruction saying it must be used with a tstat which is a little confusing. Ha.

 

David, this is the exact part I have, he sounded like a Datsun guru and Mamabears lair had quite a few very nice goodies. Have you fitted it yet, if so how does it go?

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Hi Gareth,

            I haven't fitted the restrictor as I don't have a race car yet. From what I understand the restrictor slows the flow of water and the thermostat keeps the engine at an optimum temp of 190 degrees. All the parts I have been collecting have been for later use when the occasion arises. One of the most interesting parts I purchased was a Dual point electronic distributor for an automatic Zed for $80.00. Brand new in the box but 30 odd years old. Anyway thats enough as we are getting away from the welsh plug issue.

Regards

David.  :)

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"restrictor..........needed to slow the water down to make the temp more stable"

 

Increase the pressure of the water around the head galleries is why a restrictor is used, nothing to do with the speed of the coolant.

 

Think about it for a second or two. Water boils at @87 degrees in the alpine regions for example....it's to do with the ambient atmospheric pressure. How do we increase the boiling point? Put a restrictor in the cooling system and the pressure of the coolant will increase. Now we can boil it at @120 degrees.

 

High school science stuff.  :-*

 

 

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It's not the restriction in the engine that raises the temperature.

It's being pressurized that does it!

That IS basic science.

 

Thank you Simon.  I believe it is a combination of both.  The water spending more time in the jacket has more time to absorb heat from the motor AND increasing the pressure increases the temperature at which the fluid boils.

 

In contrast, when I was racing my Alfa (much later than the 70's) I ran with no thermostat at all.  I needed to have the water getting into the radiator as fast as I could.  After all the car was designed for northern European conditions.

 

MaygZ

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Sorry, let me clarify that I meant to raise the boiling temp.

Not the engine temp.

That's not even highschool science, it's common sense.

If you are using pressurized coolant, that has a boiling temp higher than 100 degrees, and restricting it so it is in the engine longer, soaking the temp.

Of course it's going to increase the running temp.

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Hi, Just like to say that i will not be commenting on anyones questions or problems as i do not like getting into tit for tat rubbish so i will now only comment on my own projects and answer questions about my own work.

 

I believed this forum was to share experience and knowledge about the L series, not to one up other people or put them down through talking down to them or flat our being rude.

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I long suspected there was something wrong with our education system.  ;)

 

Hi, Just like to say that i will not be commenting on anyones questions or problems as i do not like getting into tit for tat rubbish so i will now only comment on my own projects and answer questions about my own work.

 

I believed this forum was to share experience and knowledge about the L series, not to one up other people or put them down through talking down to them or flat our being rude.

 

Pete,

 

Buddy, wise cracks like that speak and spell out volumes about the author, what matters is that what you put out on this forum has earned you a level of respect that few will ever be able to emulate, and as the good Reverend once said and I'm sure many of us have also thought reading that response, "Where has that button gone Gav?"

 

 

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Hi, Just like to say that i will not be commenting on anyones questions or problems as i do not like getting into tit for tat rubbish so i will now only comment on my own projects and answer questions about my own work.

 

I believed this forum was to share experience and knowledge about the L series, not to one up other people or put them down through talking down to them or flat our being rude.

 

Pete,

 

if that's your plan then the rest of us will miss out on both your wisdom and and your humour.  Please let that wise crack wash off your back.  I agree that sometimes these tit-for-tat things get a little out of hand (it can even happen to the most saintly of us).  Stepping back is the right thing, but please don't run away.  I for one need your advice and read everything you post.

 

MaygZ

 

Where did that f&cking button go???

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It's seems to be "the straw that broke the camels back" scenario.

 

Has no one else noticed the remarks between those 2? The constant undermining and one up man-ship has obviously taken it's toll on Peter's patience. 

I also hope Peter can overlook the , cough, "attempt" of humor.

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I long suspected there was something wrong with our education system.  ;)

You are not welcome here any more. Take your 280C barge & go away.

THAT is no way to speak to an ex-Gibson Racing Team engine builder - no matter what you 'think' you know...

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Whoa, where did all this come from  :'(

 

I hope I/we havent lost Peter's knowledge, expertise and friendship. He's such a generous person with his time and is a true master craftsman, the Michaelangelo of cylinder heads thats for sure!

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"restrictor..........needed to slow the water down to make the temp more stable"

 

Increase the pressure of the water around the head galleries is why a restrictor is used, nothing to do with the speed of the coolant.

 

Think about it for a second or two. Water boils at @87 degrees in the alpine regions for example....it's to do with the ambient atmospheric pressure. How do we increase the boiling point? Put a restrictor in the cooling system and the pressure of the coolant will increase. Now we can boil it at @120 degrees.

 

High school science stuff.  :-*

 

By the way Oz, the pressure in the whole cooling system, not just the head, is increased as the restrictor SLOWS DOWN the water flow.  The pump is attempting to pump the same volume of water through the system, but it is SLOWED DOWN at the restrictor and results in the increase in pressure.

 

Now I could have typed this the first time I read your post, but I didn't as see the value in blatantly pointing out your error.  I didn't see the value in hurting your feelings or embarrassing you.  Obviously now I do.

 

Don't know what high school you went to or to what level you went, but I suspect that you should have paid a little more attention in physics class.

 

As a side it doesn't matter if you can spell well, when you have nothing worthwhile (or accurate) to say!

 

And yes technically it doesn't increase the pressure in the 'whole system', but rather the part between the low pressure side of the water pump and restrictor.  I know that most would let that little exaggeration slip through to the keeper, but just in case you feel like taking on a battle of wits well outside your weight division!

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Guys I don't want to lock this thread because of a dispute. I also don't want to ban anyone and I don't think it should be necessary. Once you start banning people it becomes a slippery slope and I've seen this divide communities. Plus I'll also get a ton of personal emails I'm sure, which I don't really need :).

 

For the most part I'm sure both parties have something valuable to contribute otherwise they wouldn't comment and in this case different opinions. Sure somebody 'may' or 'could' be wrong, but you also have to remember that offline many of you guys have close relationships, so when someone outside of that immediate social circle comes in I respect that many of you will jump to defend each other.

 

Also members should show mutual respect for each other, even though at times I know this can be difficult to do and you may want to really prove someone is wrong. Comments on forums can sometimes be hard to properly interpret due to the restriction in the medium's tone, I'm sure we all know this. Just look at the fighting over YouTube.

 

It may seem obvious and perhaps optimistic on my behalf, but perhaps we should take this incident as water under the bridge and move on?

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Differences of opinion is one thing, being right or wrong another, but when it resorts to personal attacks, that's when I loose all respect for the one who does it. I'm sure everyone will move on, but that member probably will never be treated with the same respect ever again. Leaves a bad taste in your mouth...

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I hope everyone can move on. We all know how to take people, or who to listen too.

But,

That's not water under the bridge, it's Gareth's coolant.

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