GregBBRD

There's little question that a dual spring will almost always keep an engine from exploding (due to the valve dropping into the combustion chamber) when either the inner or outer breaks, if the resulting valve float issue is acknowledged and the engine is shut down soon enough. A bent valve is much better than a trash head, piston, rod, etc. Even Comp Cams (who are trying to make a market out of Beehive springs, because of the larger profit/larger market share potential) recognizes this.

20 years ago, due to the quality of wire, a single spring was simply a disaster waiting to happen....

If we are to believe the advertising people, the quality of spring wire has gotten much better and springs do not break as frequently as they did, in the past. (I personally know some drag racers that would debate this....)

However, it only takes one spring to break in an engine with single springs and the resulting damage is going to be catastrophic.

There are positives and negatives to almost anything.....this seems to be true here, also.

I always try to look at the positive points and weigh them against the negative points, before making any change.

The biggest reason to use a Beehive spring: Higher rpm potential for similar spring tensions, due to the decreased mass of the spring and the retainer. In our 928 engines, the obvious question is: "Is the engine rpm in a 928 engine limited due to the current dual spring technology?"

I'm not sure I know the answer to this.....although I turn these engines to 7200 rpms, with no issues.

Maybe Carl does and can weigh in on this. Is he turning his engine more rpms to take advantage of this factor or is this just a change for the sake of making a change? (No change in top rpm?)

ptuomov

Not speaking for Carl, but my own personal motivation for running beehives is to be able to use the lowest spring loads possible which will add to both power and to reliability.

Take the Ford Coyote design team, for example. They only spin their engine to about 7,000 rpm, but they also came to the conclusion that the best way to go is with single beehive springs and the absolute minimum spring loads:

So in my opinion it's not the case that only very high rpm engines would benefit from single beehive springs.

Fortunately, the dimensions of the older modular Ford four valve heads are very similar to the 928 four valve heads, despite obvious differences. Many mod Ford springs are drop in to the 928 with new locator disks and retainers. If the lifts and loads work out for your cams, I wouldn't hesitate for a second to run the factory stock mod Ford beehives. Whatever comes off the Ford production line is highly quality controlled, to the point that racing or aftermarket manufacturers don't even dream about it. PAC also has a good record. (In contrast, Comp packages random manufacturers' stuff so that's a lottery ticket.)

ptuomov

Spoke to a former team owner at the girls' school and Nextel Cup cars at least used to run beehive valve springs.

mark kibort

looking at the HP curves of mark anderson's engine and ones like it, it certainly doesnt look like there is any point going past 7krpm. if so, do these really address a problem. I dont think the wear is an issue, and certainly the mass reduction isnt going to be worth it at the slower engine speeds. if it corrected a problem like the video shows, sure... . but, again, from the videos ive seen at 5000 to 7000rpm, i havent see any issue .. the Behive video sure shows some problems at 5200rpm which makes me wonder if it isnt a staged test with variables workinig against a cylindrical spring set.
However, i will say, (and im not the most knowledgeable guy on this topic) i have experienced valve spring breakage and his motor was completely unharmed. in fact, those eibach competition springs were still working when we pulled the motor to replace the euro with the 5 liter. if we didnt have the head gasket problem, which was the reason (excuse) to pull and change it out to the 5 liter, we might not have known we had an issue. I think i still have the spring on my workbench.

ptuomov

The camshaft wear can be a big issue at low rpms, especially at idle. The oil film isn't there at all points and the nose is being hit with the full force of the spring. At high rpms, in contrast, the nose load on the cam is relatively low because a properly specified spring will almost loft over the nose. One should think the forces and oil film thickness issues thru before concluding when and where the high spring loads can cause problems.

Mark - If you ran double springs, one of them broke, and you didn't notice anything, don't you think that you might, just might, have been running a little bit too much valve spring to start with!? ;-) Why not use the motor to push you forward on track instead of turning that power into heat in the valvetrain?

mark kibort

I agree, low RPM is a problem, expecially with over spring rates

as far as the double springs went.... this was not my engine, it was scots.. (i just am the builder! ) it was a devek cam and spring set up, but yes, there might have been too much spring...... or the driver just didnt notice the lack of power of a leaking, floating valve of one cylinder at 4500 to 6400rpm.

now as far as power goes for the marginal difference in spring force.. i say that would be less than measurable by any stretch. total force to spin the cams, 20ft-lbs? higher spring rates, 2 ft-lbs more? (a guess) i doubt any difference could amount to more than a HP or two at worst, right

GregBBRD

That's probably a good thing....otherwise the potential market share would be very small.

From what I'm reading, it seems like about 7,000 rpms and 240 degrees of duration (at .050") is about the practical limits for this style spring. (Certainly a huge majority of 928 engines fall into this category.....which makes Carl's use of this style spring appropriate.)

Any more engine/cam than that requires more spring pressure, requiring dual or triple springs.

This, alone, pretty much rules out the Beehive spring for any high rpm engine.

Which is back to my original point that not very many current race engines are running a Beehive spring.

ptuomov

I am going to expose my confusion here. I don't understand why longer duration per se would require more spring? I think longer duration with the same lift usually requires less spring at a given rpm. There's a semi-famous study by Ricardo where they took a high revving 4-banger and made the valvetrain more stable by increasing duration. In my opinion, it's the negative acceleration of the valve motion that determines how much spring is needed. Shorter duration holding holding lift constant usually requires stiffer springs at a given rpm.

The beehive single spring was somewhat limited when they only had round wire. Now that they have egg-shape wire, the applications for which beehives are the superior option are greatly expanded. It won't be replacing the triple springs in a 500 cid two-valve pushrod drag racing motor running to 10,000 rpm, don't take me wrong. But my prediction is that the beehive design will over time take over most four-valve road racing motors, including high-revving motorcycle, that have to use metal valve springs. Higher budget than that will be pneumatic. That's not a fact, just a prediction.

For 928 4-valve motors, in particular, I'd be hard pressed to come up with a combination, street or race motor, for which custom beehives wouldn't be the superior option over custom double springs. What lift, seated load, and load on the nose would be such that it could be run on a 928 4-valve engine and that couldn't matched with beehives?

GregBBRD

You're aware that early 928 engines had single springs and Porsche switched to dual springs to eliminate severe engine damage when a spring broke?

Other than the risk of catastrophic engine failure, I agree with your thought.

ptuomov

That's with two valve engines not four valve engines, cylindrical springs not beehives, and with round wire and not ovate wire, right? If so, how relevant is that really in the end of the day to using ovate wire beehive springs in a 4v 928 engine?

Strosek Ultra

One of the most high revving standard engines, the BMW V10 5.0L do have Beehive valve springs and spherical valve lifters.
http://us1.webpublications.com.au/st...11534_18lo.jpg
Åke

ptuomov

Yes, I once owned one of those and all the 40 conical/beehive springs in it! ;-)

Strosek Ultra

Did they break?
Åke

ptuomov

;-)

The valve springs were fine. However, that M5 V10 had all sorts of error codes on every time it would go below freezing point. It was right at the emissions edge as far as I understand. Also, you could pass most other cars with that M5, but not a single gas station! It guzzled gas and motor oil like there was no tomorrow.

Strosek Ultra

Cannot believe the fuel consumption was higher than for a 928?
Åke