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Blown welsh plug


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#1 Riceburner

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Posted 11 April 2011 - 07:27 AM

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?

#2 luvemfast

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Posted 11 April 2011 - 07:52 AM

Good point about the water pump mod you did.
Maybe not necessary and not suited to high RPM's?

Why do you have a low temp thermostat?
How high pressure is the rad cap?

Also, maybe you just got an under toleranced welsh plug? How did it go in? any different to the others (easier)?

#3 Riceburner

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Posted 11 April 2011 - 08:04 AM

Cap is 17psi instead of 12.8psi standard. I ran all this stuff on the old engine except the pump without any issues for 2yrs, I run the low temp stat just so it opened earlier on track. It's the first plug closest to the timing cover which I believe is the exit of the pump to the block. They were fairly tight fit, used large socket and mash hammer to fit them.

Maybe an underdriven water pump pulley is required? From what I've read bob sharp used the LD pumps but with a restrictor instead of a stat, could the pump/stat be over pressurizing the block at sustained high revs? I shifted at 7,000 in all gears. Would an underdriven water pump cause overheating issues on the street?

#4 Zedman240®

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Posted 11 April 2011 - 09:43 AM

One thing I have done with my new motor, is get an under-driven crank pulley; if you will be revving a fair bit then might be a good idea to spin the alt and water pump a tad slower. Don't think they were designed with 6500+ rpms in mind...specialy diesel components.

#5 Riceburner

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Posted 11 April 2011 - 09:48 AM

Dimitri where did you get it from, would i be able to adapt the BMW balancer onto it? Will it cause overheating issues on the street?

I was in the pits next to your boss yesterday, he had a wicked little Renault.

#6 Zedman240®

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Posted 11 April 2011 - 09:53 AM

Its a copy of a Nismo balancer; bought it from Daniel (dazzed). Not sure if he can get any more? It's not on the car now and I do have a heating issue but I think that my cooling fan is to blame. A standard balancer is on the front of my L24 at the moment. With the underdriven one, I never had a cooling issue. I'm hoping to have it all together for the Island so we will see!

#7 Riceburner

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Posted 11 April 2011 - 02:33 PM

Do you have any pics of it Dimitri and it's size?

#8 RB30X

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Posted 11 April 2011 - 02:52 PM

I removed several balancers off L28's I wrecked and they were all different diameters?

What diameter is yours Dimitri and Gareth?

#9 Riceburner

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Posted 11 April 2011 - 04:34 PM

Mine is really hard to measure as it has the BMW 8inch damper on the front. Very rough measure seems around 125mm?

#10 KatoKid

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Posted 11 April 2011 - 06:38 PM

My brother has just finished building an LJ Torana for Group Nc. First test day at Winton it spat a welsh plug on his second lap. He replaced it at the track and its been fine since.

Welsh plugs can vary in fit and depend on how they are installed as well.

#11 Zedman240®

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Posted 11 April 2011 - 07:18 PM

Just measured my pulley, in the "V" is approx 80mm and at the top is 100mm. Outer overall diameter of the balancer is about 150ish I think...maybe bigger.

#12 Riceburner

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Posted 11 April 2011 - 09:27 PM

Maybe I could borrow the nismo balancer and get it copied? Do you know how much it's under driven by?

#13 luvemfast

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Posted 11 April 2011 - 09:58 PM

Hmmmm, I wonder who could copy it?
I'll have a look at it if you wanted.
Wasn't there a post about rebonding the balancers?
Could turn up the parts, then send them there.

#14 peter mc

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Posted 11 April 2011 - 10:24 PM

the ATI balancer is under driven . but i think it was the welsh plug at fault hear. all so check for a cracks from the hole as i have seen that before

#15 Riceburner

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Posted 11 April 2011 - 11:47 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......

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#16 luvemfast

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Posted 12 April 2011 - 07:39 AM

That Kameari balancer looks like reasonable value too.

#17 Zedman240®

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Posted 12 April 2011 - 09:34 AM

I'll post up the video later today, but Harry (my boss) had his video recording camera watching you from behind and about 150 meters before the right hand where you spun, you can see a puff of steam/smoke blow out from the drivers side then you going around the turn and losing it..

#18 RB30X

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Posted 12 April 2011 - 09:37 AM

That would be sweet.

#19 Riceburner

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Posted 12 April 2011 - 09:48 AM

Haha awesome. I was just purging the NOS before the front straight ;D

#20 luvemfast

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Posted 12 April 2011 - 10:02 AM

Hanging to see that video  ;D




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