18 replies to this topic

[phil hill]

If I remember correctly part of the reason for fitting the ball-bearing in place of the shuttle/bullet valve is to mitigate "sticking" shuttles.  In the "good old days" the fix for this was to drill through the back of the shuttle, giving any "foreign objects" trapped in the bore of the valve somewhere to go, but the power of perceived wisdom tells you that "you gotta have a ball and spring if you're building a 'performance' engine............" 

 

Other variations on the theme exist, in the MGB world they have a "tadpole" valve, which is a ball with a "tail" if you can visualise it.  The "tail" fits into the end of the spring, and this would perhaps help if the spring and ball started to cockle over in the bore, but I'm also going to assume that the seat area is to suit a ball rather than a taper.

 

I too have suffered from this "ball and spring" delusion in the past, and for a while I ran the ball-bearing with a standard i.e. non-S spring, and the oil pressure was back into the "normal" range but there were some strange pressure fluctuations.  Now I run a standard spring and shuttle, as per the original design.  

 

Phil.

[Cooperman]

For consistency with pressure the plunger seems the best option. It is possible for the plunger to stick slightly open, but this usually happens after a full engine re-build if a bit of DGS is left somewhere in the engine.

It is a good idea to polish the outside diameter of the plunger with very fine wet & dry and some metal polish and ensure that it slides in and out freely when doing the 'dummy build'. 

If you wish, a small washer can be fitted in the closing cap to slightly increase spring loading and I usually do this on my engines.

90 psi is a good pressure at cold, dropping when hot to around 20 to 25 at tickover, 50 at 3000 rpm & 65 to 70 at 6000 rpm. That is using a top quality 20w50 oil like Valvoline VR1 or equivalent.

[Spitz]

I happened to check my valve the other day.  My pressure would drop fairly low (40lb) while hot.

I replaced the valve with a new of the same and a new spring.  The new spring was about 5mm longer than the old one.
Pressure is much much better now.

 

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[Earwax]

If you choose to use the ball and spring mod... ( and the reasons for and against are stated above) it is usual to chop a coil or two from the length of the spring and it is beneficial to place a rod within the spring... something like the threadless shank of a long bolt,   and usually at a  length equivalent to the diameter of the ball shorter than the actual spring ( ie inserts inside the spring and allows full opening but then prevents the spring from bending and possibly catching

 

this generally eliminates the sticking problem.  ( apologies for complicated wording... and i don't have one nearby to measure sorry.)