Balancing Valves

[DSPTurtle]

I might be way way out on the bell curve with this one...
Although intake and exhaust valves aren't being countered by a weight on the other end, the forces of the valves going up and down at a high rate of speed might make a difference.
What I found is that all of the exhaust valves are within 0.5g. However, on the intake side, the valves can vary by as much as 3g. Would it matter, should I even try... which brings me to the question... how would you remove 3g of weight from an intake valve without compromising the integrity?
Anyone ever wrestled with this one?

[Trackrash]

Originally Posted by DSPTurtle

I might be way way out on the bell curve with this one...
Although intake and exhaust valves aren't being countered by a weight on the other end, the forces of the valves going up and down at a high rate of speed might make a difference.
What I found is that all of the exhaust valves are within 0.5g. However, on the intake side, the valves can vary by as much as 3g. Would it matter, should I even try... which brings me to the question... how would you remove 3g of weight from an intake valve without compromising the integrity?
Anyone ever wrestled with this one?

Old school hotrodders would "lighten" the valves. I have done this before. It amounts to thinning the valve on a lathe toward the valve face. I did this on my 2,2 build many years ago. It is mostly done to aide flow, but has the side benefit of less inertia. The valves on the newer motors don't have room, from what I can tell, to do this. I just finished my 3,0 rebuild and was hesitant to remove any material from those valves.
I imagine racers probably do it all the time.

[michael lang]

That is a very interesting observation JB, I have to admit something like that had never crossed my mind. I guess I have always believed that lightening the valves is one of those unchangeable variables. Goes to show you, how creative you have to be for lighter = faster.

[prschmn]

I don't think I'd try getting 3 grams off a Porsche valve-but there's always Titanium!

[safe]

Light valves are good!
Change out the valves and use valves with 8 mm stems like the 993.
I don't think an imbalance between the vales matter much. There is a huge difference between intake and exhaust valves...

[DSPTurtle]

Good point on the delta between the intake and exhaust valve weights. And since the spring pressures and install lengths don't vary, I guess they are treated as individual bodies in motion. Hmm... I guess I'll have to find something else in the stock valve train to improve on. However, the inertia of a heavy valve would have it traveling with more force and hammering away on the guide.
But yeah, lighter valves would certainly be better.

[safe]

Originally Posted by DSPTurtle

Good point on the delta between the intake and exhaust valve weights. And since the spring pressures and install lengths don't vary, I guess they are treated as individual bodies in motion. Hmm... I guess I'll have to find something else in the stock valve train to improve on. However, the inertia of a heavy valve would have it traveling with more force and hammering away on the guide.
But yeah, lighter valves would certainly be better.

The easiest way (and probably cheapest) is to use titanium retainers, half the weight of the stock.
But the best way is ta change valves. Then you can not only get lighter valves, you can get some with a "flatter" backside that will improve performance of the head.

[stownsen914]

Lighter is better when it comes to valves, but I've never heard of balancing them. I wonder if it matters as much since they're not reciprocating.

[WERK I]

Valves are not a rotating medium so balancing is unnecessary. Lightening valves is done to reduce the effects of inertia.

[KTL]

I've seen titanium valves are around $65 each. In a GT3 four valve motor, that gets expensive fast. I suspect since the two valve 911 engines have larger valves, the material cost makes them even a bit more expensive?

I believe you also need to replace your valve guides with a different material to complement the titanium valves?

[prschmn]

Guides aren't a problem but seats are. You need to use Cu Br-but beryllium
is banned-there are replacement alloys though

[KTL]

Thanks for the correction Mark