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Blown welsh plug


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#21 Zedman240®

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Posted 12 April 2011 - 12:28 PM

Just uploaded; its about 3:45 in...hope the link works!



#22 RB30X

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Posted 12 April 2011 - 01:05 PM

You're Luckily you spun and rolled out of the way. Had a few cars up your rear.

#23 Gareth. J.

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Posted 12 April 2011 - 01:21 PM

I gave it some gas when it kept spinning so flicked to the inside then stalled and rolled backwards. Renault goes good, got a nice sound to it!

#24 mossy

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Posted 12 April 2011 - 02:28 PM

Ha, I have a guy in mordialloc who has done all my brake work really cheap but if your offering Simon. Thanks, david + peter that makes me feel a bit better about it. I had a really good look at the track on sunday and it all looked ok, the hole was very clean. Bit off topic but I also saw a Kameari balancer for about $380, The ATI balancer is out of my budget at the moment. I might just see how it goes with the current setup for the time being, and I'll make sure I have welsh plugs in my spares bag......


Gareth the ATI balancer isn't that much more, I just bought one, it was about $490 posted

#25 Gareth. J.

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Posted 13 April 2011 - 09:11 AM

Thanks mossy, whereabouts did you source it from? I'm guna try what I have (bmw8") and fit the don potter water restrictor.

#26 mossy

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Posted 13 April 2011 - 11:30 AM

I got mine direct from ATI, they were pretty easy to deal with

#27 ozconnection

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Posted 13 April 2011 - 07:40 PM

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.  :)





#28 peter mc

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Posted 13 April 2011 - 07:46 PM

It's a bit of a shame Gareth coz you were fairly flying!!!
It looked like you were pulling away from the Renult

#29 Gareth. J.

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Posted 14 April 2011 - 06:48 PM

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.

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#30 ozconnection

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Posted 15 April 2011 - 05:14 PM

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.  ;)



#31 Enzo

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Posted 15 April 2011 - 10:36 PM

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 :)

#32 Gareth. J.

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Posted 15 April 2011 - 11:00 PM

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?

#33 Enzo

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Posted 16 April 2011 - 09:54 AM

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.  :)

#34 ozconnection

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Posted 16 April 2011 - 04:22 PM

"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.  :-*



#35 luvemfast

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Posted 16 April 2011 - 07:21 PM

It's not the restriction in the engine that raises the temperature.
It's being pressurized that does it!
That IS basic science.


#36 MaygZ

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Posted 16 April 2011 - 07:27 PM

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

#37 luvemfast

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Posted 16 April 2011 - 07:46 PM

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.

#38 peter mc

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Posted 16 April 2011 - 10:28 PM

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.

#39 Sirpent

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Posted 16 April 2011 - 11:08 PM

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?"



#40 MaygZ

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Posted 16 April 2011 - 11:56 PM

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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