14 replies to this topic

[Gaz66]

As title folks.
Just thinking ahead.
Cup or ball?
Also has anyone drilled and tapped the cap to make the blow off adjustable?

Edited by Gaz66, 07 February 2025 - 04:54 PM.

[imack]

I'm still running the one I made almost 40 years ago. Drilled and tapped the cap and machined the top surface flat. Modified a 5/16 unf bolt, turned the hex head so it's round and machined a step into it to locate the spring. Cut a screw driver slot for adjustment. Fibre washer between the nyloc and the cap to seal. Shortened the spring to suit. I've run a ball bearing from a c/v joint since the 80's and not had issues, but I know they're often not recommended.

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Edited by imack, 07 February 2025 - 05:49 PM.

[nicklouse]

Have read. https://www.theminif...huttle-vs-ball/

[Gaz66]

I read that Nick which is what inspired this thread.
It seems, as usual, there are pros and cons with each.
I've never used the ball bearing myself having always used the cup which was on the whole good but did once jam with a bit of crap and on investigation was scored quite severely.
I'm tempted to give the ball a go as and when.
Decisions decisions 😁

[imack]

I switched to a ball in the 80's when I fitted my first absolutely knackered £10 austin 1300 engine to my mini. It had no oil pressure, did 50 miles to a pint of oil, the syncromesh was weak and the standard relief valve shuttle stuck open virtually every time I used the car. The ball bearing virtually eliminated the sticking problem. But, the bottom end let go while racing an XR2 off the lights on the way home from college.
I've continued to run the ball bearing ever since.
If you decide to run the ball bearing you'll need to shorten the spring or you'll have 100+psi at idle.

[Spider]

For a Race Engine where they tend to live most of their time north of 4000 RPMs, I'd suggest a Ball, though, if you are running a Dog Box, then really, either would be fine.

 

If you do use an adjustable valve, don't be tempered to set it too high, in fact, I'd suggest going the other way if you are looking for power. 40 PSI with the oils available today is loads (in fact, the MPIs were set around 35 PSI if memory serves). Having a higher pressure than what's needed only saps power and heats the oil.

[Gaz66]

I'm curious.... What is the relevance of the dog box?

[Spider]

I'm curious.... What is the relevance of the dog box?

 

The debris that jams the standard shuttle in the Relief Valve is what's worn from baulk rings, that's all that fury fuzz on the magnet of the sump plug.  No baulk rings, no fuzz and so the relief valve is way way less likely to jam.

[Gaz66]

I'm curious.... What is the relevance of the dog box?

The debris that jams the standard shuttle in the Relief Valve is what's worn from baulk rings, that's all that fury fuzz on the magnet of the sump plug. No baulk rings, no fuzz and so the relief valve is way way less likely to jam.

Obvious really, and bits of selector hub dogs from those grindy changes 👍

[Gaz66]

What's the advantage of using this little spacer/cup?
https://www.ebay.co....emis&media=COPY

[KTS]

..presumably the cup is intended to keep the ball centred ?

[Gaz66]

..presumably the cup is intended to keep the ball centred ?

I would have thought the spring alone would have kept it centered.
All I can see it doing is upping the oil pressure .
Unless that is the intention.

[imack]

If you buy the ball and spring kit from minispares and fit it as supplied you'll find the oil pressure is way too high. You'll need to shorten the spring.
I'm guessing that most adjustable oil pressure caps will req a standard spring to be shortened too, my homemade version certainly does.
Maybe the one you're linking to is a ready made shortened spring, possibly used without the additional cup if you have an adjustable pressure cap, and with the cup for a standard cap.

[Gaz66]

It says in the description that the spring may need cutting down so I'm presuming it's standard length.

[Spider]

..presumably the cup is intended to keep the ball centred ?

 

I'd say so. The ball being what it is, the springs don't want to sit on centre, they always sit off to one side.