Describe Your Single Mass Experience
09-24-2017, 09:15 PM
#1
Safety Car
Thread Starter
Describe Your Single Mass Experience
Background: I converted my 95 to a 6 speed and the original intent was a 650 rwhp blown 383 lt4. I chose a McLeod street twin for my clutch on a steel flywheel. This is a twin disc clutch without a sprung hub. I later decided to save the supercharger for a future project and went with a milder cam and higher compression.
I did not give much thought to the clutch when I revised my build and now I'm not happy with the noise and vibration transmitted by the unsprung clutch. I know there is some noise in neutral that will be there regardless, but how much vibration will be transmitted at lower rpm in higher gears?
Please describe what setup you have and how it sounds and feels between 1000-2000 rpm . Also include how large your cam is for reference.
I'm worried that I'm going to drop another $800 on a clutch and end up with the same noise and vibration I have now.. Thanks for any info in advance.
I did not give much thought to the clutch when I revised my build and now I'm not happy with the noise and vibration transmitted by the unsprung clutch. I know there is some noise in neutral that will be there regardless, but how much vibration will be transmitted at lower rpm in higher gears?
Please describe what setup you have and how it sounds and feels between 1000-2000 rpm . Also include how large your cam is for reference.
I'm worried that I'm going to drop another $800 on a clutch and end up with the same noise and vibration I have now.. Thanks for any info in advance.
09-24-2017, 10:32 PM
#2
Running a Spec steel (SC05S) with a dual friction Centerforce clutch disk and a GM LT4 race pressure plate. Normal driving there is no tranny noise except for some rattle if idle in neutral.
Cam is 565 lift 280 advertised duration and 110 sep angle.
I did use my old auto flex plate to match balance the Spec flywheel (it was off 18 grams), no flywheel vibration.
Cam is 565 lift 280 advertised duration and 110 sep angle.
I did use my old auto flex plate to match balance the Spec flywheel (it was off 18 grams), no flywheel vibration.
Last edited by blue94; 09-24-2017 at 11:11 PM.
09-24-2017, 11:07 PM
#3
Melting Slicks
96 LT4 with "Hot Cam", Spec lite weight billet steel flywheel, Spec Stage 3 plus disc and pressure plate. love it; some rattle at the very beginning but after a few miles, and I suspect the springs in the sprung clutch disc had a chance to soften up a bit, it was pretty normal sound wise and I really like the way a metallic clutch locks up ....maybe not for everyone, but it matches my driving style. 
09-25-2017, 09:05 AM
#4
Le Mans Master
I had a SPEC setup on my '96.
I had problems. see
https://www.corvetteforum.com/forums...h-chatter.html
I had an SC05S-2 flywheel which is the heavy steel one piece flywheel. Blue 94 said his SPEC was off 18 grams. Mine was off 20 grams. That resulted in a bad vibration at about 3k rpm and up. It would shake really bad.
I did not notice the transmission rattle that is common to ZF transmissions with that flywheel.
Your question was about 1k to 2k sound and feel. In that range I did not notice any noise and it felt solid. In other words except for while the clutch was engaging the car drove normally in that rpm range with no unusual noise or vibration.
I had a SPEC stage 2 clutch disc and pressure plate. It was the worst chatter on any car that I had ever driven.
I bought the car used with that setup so I don't know how it was installed or abused before I got it. This was a 40k mile car and I suspect the clutch had very few miles on it, but it had a lot of bad heat spots on the flywheel and pressure plate showing uneven contact/grip. The disc was trashed with scorched marks and uneven wear with a step.
I replaced it with a stock original setup and it has been working great since. I also cleaned up the SPEC flywheel and had it balanced. I expect I will use it again.
On your setup I would be concerned about not having a sprung disc with a solid flywheel. There is no cushioning when you let out the clutch. I would think it would create a vibration and a jerkiness (is that a word?). I have dealt only with street cars where your high hp car clutch requirements might be a little different.
Good luck.
I had problems. see
https://www.corvetteforum.com/forums...h-chatter.html
I had an SC05S-2 flywheel which is the heavy steel one piece flywheel. Blue 94 said his SPEC was off 18 grams. Mine was off 20 grams. That resulted in a bad vibration at about 3k rpm and up. It would shake really bad.
I did not notice the transmission rattle that is common to ZF transmissions with that flywheel.
Your question was about 1k to 2k sound and feel. In that range I did not notice any noise and it felt solid. In other words except for while the clutch was engaging the car drove normally in that rpm range with no unusual noise or vibration.
I had a SPEC stage 2 clutch disc and pressure plate. It was the worst chatter on any car that I had ever driven.
I bought the car used with that setup so I don't know how it was installed or abused before I got it. This was a 40k mile car and I suspect the clutch had very few miles on it, but it had a lot of bad heat spots on the flywheel and pressure plate showing uneven contact/grip. The disc was trashed with scorched marks and uneven wear with a step.
I replaced it with a stock original setup and it has been working great since. I also cleaned up the SPEC flywheel and had it balanced. I expect I will use it again.
On your setup I would be concerned about not having a sprung disc with a solid flywheel. There is no cushioning when you let out the clutch. I would think it would create a vibration and a jerkiness (is that a word?). I have dealt only with street cars where your high hp car clutch requirements might be a little different.
Good luck.
Last edited by QCVette; 09-25-2017 at 09:08 AM.
09-25-2017, 09:42 AM
#5
Le Mans Master
Rattle in neutral will depend on several variables besides the flywheel design. Total weight of the flywheel and pressure plate will make a difference: heavier is quieter. Also, how rough your engine idles and at how low an rpm will make difference: the smoother and higher the idle rpm the quieter. I have a 396 with significant cam overlap, and 13lb Findanza flywheel, and a lighter GM racing Valeo pressure plate, with a sprung-hub disk, idling at 1000rpm. It's probably moderately loud as these things go, but that's a pretty light flywheel/pp combo that I'm running. Yours would be much heavier.
But...I would not use a solid (un-sprung) disk. Once you ditch the dual-mass, you will want the sprung disk hubs for quietness and for smoother engagement. I don't know if there's an option for sprung disks on your McLeod pressure plate, but I'd try to find out if I were you.
But...I would not use a solid (un-sprung) disk. Once you ditch the dual-mass, you will want the sprung disk hubs for quietness and for smoother engagement. I don't know if there's an option for sprung disks on your McLeod pressure plate, but I'd try to find out if I were you.
09-25-2017, 10:27 AM
#6
I run the Spec Stage II clutch (disc and pressure plate). This is combined with the Fidanza aluminum FW like Matthew above. My disc is a spring hub. I get some transmission noise, but not bad at all. I moved my ide speed up to 1,000 RPM as I run the ZZ9 roller cam. 112 lobe sep; fairly mild. The engine idle speed at 1,000 RPM is actually nice. It's a smooth idle with that cam and it really mitigates the transmission noice while in neutral with the clutch disengage. The sound from the ZF at ide w/o the clutch engaged is like a smooth "whirl" almost like a blower wind, but not too pronounced at all.
09-26-2017, 06:50 AM
#7
Le Mans Master
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Seems pretty common that if you deviate from a stock idle and the DM FW, a lighter (single mass) FW and a sprung hub disc coupled with higher idle is SOP, but some transmission rattle is to be expected!
If your O2 sensors are the least bit "iffy", the idle can be rougher than normal - same goes for boarder line coils, wires, injectors and plugs.
On a 500 clutch hp ZR-1 (for example) in 4th gear, there is a 12 rwhp increase due to reduction of rotating mass (Fidanza weighs in at around 13# as opposed to over 40# for the dual-mass unit.) AND, the greater the acceleration rate, e.g., first gear, the greater the effective hp due to reduction of rotating mass (once the clutch is fully engaged).
Right away you'll feel the result of the lighter FW.
On the negative side, it took me a few days to readjust to the additional throttle needed. The heavier FW "stores" more energy and smooths the transition especially from a stop. But, after a couple days I no longer give it a second thought.
On the positive side, I love the snappier throttle response - especially in the first couple gears. More of the motors' "grunt" goes immediately to the wheels instead of spinning up a heavy FW. (In spite of having drag radials on the car, I'll often "get rubber" by just depressing the accelerator - in low gear [especially].)
Not everyone likes the light, single-mass FW. Some prefer quiet and the easier clutch engagement. But, even the very noticeable rattle my wife's cammed (read: overlapping) Z makes at a stop light (in neutral), I like the "snappiness" of the throttle response.
If your O2 sensors are the least bit "iffy", the idle can be rougher than normal - same goes for boarder line coils, wires, injectors and plugs.
On a 500 clutch hp ZR-1 (for example) in 4th gear, there is a 12 rwhp increase due to reduction of rotating mass (Fidanza weighs in at around 13# as opposed to over 40# for the dual-mass unit.) AND, the greater the acceleration rate, e.g., first gear, the greater the effective hp due to reduction of rotating mass (once the clutch is fully engaged).
Right away you'll feel the result of the lighter FW.
On the negative side, it took me a few days to readjust to the additional throttle needed. The heavier FW "stores" more energy and smooths the transition especially from a stop. But, after a couple days I no longer give it a second thought.
On the positive side, I love the snappier throttle response - especially in the first couple gears. More of the motors' "grunt" goes immediately to the wheels instead of spinning up a heavy FW. (In spite of having drag radials on the car, I'll often "get rubber" by just depressing the accelerator - in low gear [especially].)
Not everyone likes the light, single-mass FW. Some prefer quiet and the easier clutch engagement. But, even the very noticeable rattle my wife's cammed (read: overlapping) Z makes at a stop light (in neutral), I like the "snappiness" of the throttle response.
09-26-2017, 10:19 AM
#8
Safety Car
Thread Starter
Thank you, everyone, for sharing your experience and giving me some hope.
Paul, the O2 sensors are new, AC Delco, just to rule out any issues with them. The overlap of the cam makes it load up with fuel at idle, so I just run it in open loop. The rest of the ignition system is fairly new as well.
At steady speed at 1800 rpm on the road, you can feel the pulses of the cylinders firing and hear the input shaft of the transmission rattling back and forth. A little over 2200 rpm it all goes away and its smooth and quiet. I know there will still be noise at idle and that noise does not bother me nearly as much as feeling the pulses and hearing the noise just driving down the road when I'm not on it.
I'm swapping the cam to a smaller one with less overlap, so I know that will help.
Throttle response, its very responsive right now. The twin disc pressure plate is fairly heavy--I've never had a stock C4 pressure plate in my hands, so I can't comment on how the entire assembly compares.
Paul, the O2 sensors are new, AC Delco, just to rule out any issues with them. The overlap of the cam makes it load up with fuel at idle, so I just run it in open loop. The rest of the ignition system is fairly new as well.
At steady speed at 1800 rpm on the road, you can feel the pulses of the cylinders firing and hear the input shaft of the transmission rattling back and forth. A little over 2200 rpm it all goes away and its smooth and quiet. I know there will still be noise at idle and that noise does not bother me nearly as much as feeling the pulses and hearing the noise just driving down the road when I'm not on it.
I'm swapping the cam to a smaller one with less overlap, so I know that will help.
Throttle response, its very responsive right now. The twin disc pressure plate is fairly heavy--I've never had a stock C4 pressure plate in my hands, so I can't comment on how the entire assembly compares.
