Topic: big bore drag motor, beehive springs warranted?

[gschuld]

So lets take, for example    a fresh build motor: 73mm bore, carrillo rods, 12.5:1 compression lightweight pistons(190 gram bare per piston), reworked RC ported head, 327 cammed motor, stock stroke.
1060cc.

Frankie runs something similar and has the shift light set at 10,000rpm, shifting at +/- 10,200 max ideally and has the high side Rev limiter set at 11,000 to handle missed shifts.  He is running RC steel rods and heavy 245 gram (bare weight) vintage MTC 72mm pistons.  He has reported no problems with valve float or bounce control at 11,000 with conventional double spring type APE springs and I'm guessing titanium retainers (?).  He has QUITE a few years with this setup without issues.

The 73mm motor would have pistons that weight a full 55 grams less per piston, and rods more than 25% lighter. Same 327 cam.  Head flowing ability should up even or better.  His power is dropping off at about 10,000rpm.

If starting from scratch, would Cycle X beehive springs be a worthy investment for added piece of mind at the 11,000rpm zone, or are conventional springs with titanium retainers sufficient?

Beehive springs have, on paper anyway, several potential benefits.  Significantly lighter overall spring/retainer weight, virtually no resonance potential since each wind of the spring is a different diameter, spreading the harmonics out.  Lighter overall spring pressure is required for the beehive springs, so along with the lughter weight, potentially less wear on valves/guides, rocker, and cam lobes.  And testing has supported the idea that the lighter beehive spring/retainers and lower seat pressures tend to allow a modestly extended rpm range past where conventional springs start to give up, assuming the conventional springs are starting to loose precise control of the valve action.

This is all theory to me, no practical experience.  Beehive springs are certainly the more expensive option, but at what point are they worth it, considering the three main potential benefits:

1 Potential added high rpm safety factor from valve float/bounce (a rev limiter is a given here BTW)
2 Potential for extending the power band up a few hundred rpm or so  for added performance.
3 Potential for reduced stress and wear on the rest on the valvetrain.

So who has an opinion on this?

George

[bwaller]

I haven't been able to find any for mine so I have no beehive experience, but I would indeed make the switch. I think the big issue is flow and whether higher revs make any extra power (unlikely above 10K). Otherwise it's extra wear & tear for nothing.

So there I didn't answer a thing George.   

[Old Scrambler]

I used FERREA valve and spring components to convert my F2 head. The stems are 5.45mm. I replaced the exhaust valves with the 31mm SS units with flat faces. The intakes went up one size to 35mm. Rather than sinking the valves into the seats, we re-cut the seats and bored the throats hoping for compression and flow gains. We cut new colet-groves to keep seat pressure at recommended levels with allowances for the lash-caps. The cam has .408-inch lift with long duration (not quite what was advertised) and lobe-centers are at 110-degrees. I was told that although wider lobe centers tend to lower the torque-curve, that is related to how high the the RPMs go with  good HP. We degreed the cam at standard spec to avoid valve-interference on the overlap. With light-weight trial-springs in the motor, we had clearance..........so on final assembly we were more confident of clearance issues...........and found none.

With the bee-hive springs we have room for more lift (if wanted) before touching the valve-stem seal............and we have more confidence at maximum rpms (11,300) because everything is lighter. If I was drag-racing and was at the shift point but a tenth of a second short of the stripe.........I'd keep reving for the WIN

btw....my cost for the complete valve train was no more than the Kibblewhite-Cycle-X packages.......including the special machining to cut my valve-stems to the proper lengths. The only reason I did not use the Cycle-X kit was because we wanted a larger intake valve.   

[gschuld]

Well, it's a start.    I know there are some out there, like Old Srambler, running beehives in the 11,000 range.  For the most part, people seem to be using conventional springs. 

I really like the idea of the potential for less wear and tear on the rest of the valvetrain.  I've give the same priority to reducing the weight of the pistons and rods, reduces stress and wear and tear.  The wear and tear on the rocker to valve tips and rocker to cam lobes could potentially really benefit from the lighter weight and pressure.  Perhaps I'm just looking for an excuse to go unnecessarily overboard. 

I've seen me do it before.... ....

George

[gschuld]

Dennis,

Thanks for the quick reaction time...  I'm leaning toward the Cycle X beehives set, but for a ported k head rather than your f head.  The RC 327 cam has a "modest" .365 lift, well under your cams .408 lift.  I don't see any down sides short of the reportedly very unlikely potential of a spring breaking.  If a single spring beehive breaks, the valve takes a death dive for the piston.  With a conventional double spring, there is a chance that a broken spring will not drop the valve since the second is still operating, but better catch it quick...

11,300 rpm, makes me pucker up a bit...  where is your peak power?  10,500?

Grorge

[scottly]

George, if one spring breaks at 10,000 RPM, the other spring will be too weak to prevent the valve from floating and crashing into the piston.

[TurboD]

It is possible with some engine designs to survive under certain conditions, I have broken valve springs in race car engines without any other damage.

As Scottly said, if a spring in a sohc should break at 10k, bigger problems are soon to follow. lol

[Don R]

 I haven't heard much of a problem with harmonics in these  sohc  engines but I have some experience with harmonics in my 567" big block. After a cam change the first set of springs broke one at 35 passes, the next set broke one at 30 passes. We talked to some spring companies and harmonics were determined to be the culprit. We put in a different brand and shimmed them tight to recommended pressures and distance from coil bind, so far about 100 runs with zero problems.

[Bill/BentON Racing]

Seems like my Triumph TR4A had 3 valve springs on exhaust side. Any motorcycle's ever had 3? ......I neve floated one on them! Lol, Bill

[MRieck]

I haven't been able to find any for mine so I have no beehive experience, but I would indeed make the switch. I think the big issue is flow and whether higher revs make any extra power (unlikely above 10K). Otherwise it's extra wear & tear for nothing.

So there I didn't answer a thing George.   

Right...you are spinning the $hit out it for nothing except exponential wear and tear on parts. Dennis's 35mm valve with heavy porting/throat boring, 110 LC cams etc probably will get you some a bit after 10,000... I'd like to see a dyno chart where it does end. Custom cutting the keeper groove lower on the stem is certainly a good idea to get spring pressure up.
 Even if you are using a 34mm valve power peaks around 9500RPM in my experience. It won't drop off which is good for overrun but there isn't anymore there. I
 I know it has that "exotic" sound to it....."I rev it to 12,000, 13,000 RPM" but it doesn't do anything unless the engine is truly exotic. Maybe I am jaded by working with 600cc engines in the past where you can rev them to 15,000 RPM

[Bill/BentON Racing]

Yep, dyno and track verify. 9500-10,000 hp peaks,  Mikes heads just keep it there a good bit longer,  most nosedive dramatically by 9500. Mike's levels out @ 10,000, stays steady til 11,200 where we cut the run. I'd luv to see a dyno run and see one making power increasingly to 11-12000 . Bill

[gschuld]

Yep, dyno and track verify. 9500-10,000 hp peaks,  Mikes heads just keep it there a good bit longer,  most nosedive dramatically by 9500. Mike's levels out @ 10,000, stays steady til 11,200 where we cut the run. I'd luv to see a dyno run and see one making power increasingly to 11-12000 . Bill

And you had no issues at 11,200rpm with your setup?   At what rpm are you "getting into trouble", resulting in valves not doing what you want them to anymore?

Is there a viable wear and tear reduction benefit (my main interest) for our motors with beehive springs?

George

[dragracer]

At 10 grand in high gear, you can tell that the bike stops making power although it doesn't nose over. I don't shift anything I own above 10,000rpm. Engines range from my small 1030 up to our 1500cc engines. If I can't get it done at that rpm, it's time to either tear it down to figure out what's wrong, or quit racing. I'm talking 8 valve engines, not 16 valves that like higher rpms. My ZX10 makes power up to the point of bouncing off the factory rev limiter. I'm going to have it reflashed to extend it when I put the engine back together with high compression pistons and a thin head gasket. Should really scream then.

[dusterdude]

Listen to frank,"my small 1030 engine",now thats funny.1030 isnt small buddy

[Medyo Bastos]

i love the sound when it revs to just before i start smelling shiiit, even if it stops making power!