O.P. Relief Valve Failure

[1600dave]

Don't hold me to it (been 12 months since I built my engine), but from memory a 3/4" welsh plug does the trick. I just measured a spare L18 block, and the hole is 19mm, I would assume it'll be the same on an L6. I remember having to slightly chamfer the leading edge to get it to start in the hole.

 

I tapped and fitted threaded plugs to all the other oil galleries in my engine, can't remember why I didn't do this one the same way ? Maybe it was too large for the taps I had on hand and I was too tight to buy another one 

 

I installed the welsh plug "upside down" as shown in one of the various Datsun mod books (can't remember which one) - ie hollow side inwards, use a socket just smaller then the hole to knock it in carefully then tap it right in the centre with a flat punch (again as per the book I had). The idea is it will tighten it a little by taking some of the "roundness" out of the plug. Don't know if it really helps, but won't hurt (unless you whack it hard enough to knock it right in or crooked, etc).

[RB30X]

So where do you get welsh plugs from.

[peter mc]

repco  or any auto shop sell them

[jamo240]

Hey guys

 

I haven't seen anyone identify a mode of failure here...what caused the relief valve to fail and come adrift? It's unlikely to be pressure, as that is not much higher than standard. So is it vibration? If it is, then why not stake the block where the valve is retained...this might allow you to retain the valve's function while reducing the likelihood of it failing??

 

When I was at Nissan Motor Sport in the Skyline days, I saw some dumb things done to race engines on the basis they were a race engine, and therefore had to change everything away from factory designs....as often as not, the factory setup could be made to work just fine provided it's function was adapted to the competition application. The complete removal of factory installed systems should be done with due consideration, as the factory does not include these systems because they like wasting money on unnecessary parts!

 

Cheers

 

Jamo

[peter mc]

the valve does not come adrift .the ball falls out when the front of the valve cracks more to do with age of the part i think. but the one that failed in my race engine was about a year old . the only thing i will say if you do this mod is change you oil filter often as it will see all the oil now that the bypass has gone

[Wayne G]

Well said Jamo! Unless you are a serious racer, and there seems to be a few around this site, the factory spends many hours doing R&D and testing and a weekend warrior, myself included, thinks they know better?

 

This valve is in place to maintain oil supply to engine with a blocked filter. Most vehicles owned by people on this site probably maintain their vehicle enough that this will never happen, but the valve also opens sometimes when the engine is cold too. This valve fails from age/vibration/heat and can likely be purchased new from Nissan at an economical price.

 

To either have engine failure from lack of oil due to blocked filter or engine failure from the valve failing and probably blocking the oil gallery, that is the question?

 

For what is is worth, I have built many race engines and even more street engines. Race engine always have the oil filter bypass valve removed because I want every bit of oil filtered and hopefully the operator is more aware if an issue arises.

[luvemfast]

I have one of Neil Cartlidge's old blocks that I'm building up.

It has s brass welsh plug, looks to be about 10mm and is inserted normally, not backwards.

 

If Neil did it, it's good enough for me or anyone else!