C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Single Mass help!!!!!

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Old Nov 8, 2004 | 11:58 PM
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Default Single Mass help!!!!!

I just fired the stroker tonight and was greated by what sounded like a bad od knock. After carefull inspection and turning the motor over without fuel/Ignition the problem was isolated to the clutch. The motor will fire and run great but if the cluch pedal is depresed more then 3/4 somthing is knocking bad. I have a new Fidenza FW and Spec stage 3 clutch and am at a compleate loss as to what could be wrong. This was bought as a kit and came with all the bolts for both the P/P and FW as well as the new TO bearing. It looks like I am going to have to drop the trany but sugestions would be a huge help.

THKS in advance

Last edited by FD2BLK; Nov 9, 2004 at 12:33 AM.
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Old Nov 9, 2004 | 12:47 AM
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I have a Fidanza on mine -- didn't have any clearance issues. The noise you're talking about isn't the 'normal' single-mass noise. That's more like shakign a box of rocks and only happens with the clutch engaged (foot off the pedel) in neutral.

Definitely re-check the torque on everything. Make sure the clutch fork is properly seated on the throw-out bearing. Also, that the throughout bearing is secured on the pressure plate spring with the c-shaped wire clip.

Also make sure you tightened the ball stud all the way (to tighten, you have to turn it counter-clockwise) and also tighten the locking screw (clockwise). If the stud is loose, the clutch fork could be hitting the pressure plate.
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Old Nov 9, 2004 | 05:40 AM
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Originally Posted by FD2BLK
I just fired the stroker tonight and was greated by what sounded like a bad od knock. After carefull inspection and turning the motor over without fuel/Ignition the problem was isolated to the clutch. The motor will fire and run great but if the cluch pedal is depresed more then 3/4 somthing is knocking bad. I have a new Fidenza FW and Spec stage 3 clutch and am at a compleate loss as to what could be wrong. This was bought as a kit and came with all the bolts for both the P/P and FW as well as the new TO bearing. It looks like I am going to have to drop the trany but sugestions would be a huge help.

THKS in advance
If you push in and hear a knock, your clutch fork is probably hitting the Pressure Plate, do you have shavings on the ground under the bell housing?

If you push in all the way and the engine RPM goes down or it trys to stall, then you are hitting the PP for sure.
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Old Nov 9, 2004 | 10:38 AM
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Originally Posted by ld85
If you push in and hear a knock, your clutch fork is probably hitting the Pressure Plate, do you have shavings on the ground under the bell housing?
If you push in all the way and the engine RPM goes down or it trys to stall, then you are hitting the PP for sure.
I was thinking the same thing since the P/P and FW are bolted togeather and rotate togeather the shift fork is the odd man out. I am sure somthing is hitting the shift fork or the shiftfork is hitting somthing but am at a compleate loss as to how or why. I called Spec and had them double check my order and the correct FW and clutch was sent as well as the right bolts. I am woundering if the rod that goes into the slave cyl may have goten off and sliped out of the hole cuasing the rod to extent to far and will check that later on.
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Old Nov 9, 2004 | 01:54 PM
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i think a pivot ball stud that has backed out, or the use of the "long" pivot ball stud, would cause the fork to hit the pressure plate after depressing the clutch pedal about 1/2 to 3/4 of the way (with your clutch and flywheel set up). did you change the stud? if not, check to see if it has backed out.
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Old Nov 9, 2004 | 03:26 PM
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The pivot ball is the #1 suspect at this time. I did not change the pivot ball because the kit was suposed to be a direct replacment but I am now thinking either the pivot ball backed out as stated or the FW/ P/P combo is wrong and needs the shorter ball
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Old Nov 9, 2004 | 03:38 PM
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SPEC had this problem with their ZR1 clutches a couple of years ago...

I don't like their clutches... namely, cause they sent me a bad one... horrid customer service.
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Old Nov 9, 2004 | 05:23 PM
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Here is what I think,,

I know for fact that there are 2 overall lengths of ZF6 Bellhousings. One is 5.875 and one is 6.125, if you have the shorter model, you are likely going to hit the Pressure Plate with the back of the fork. They have the same part number which is really weird

Mine is 5.875 but I relieved the back of the fork slightly to clear. Coud be wrong, but it makes sense.
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Old Nov 9, 2004 | 07:58 PM
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Hmmmmm,
I find that very interesting I do have the shorter 5.875 belhousing. ID85 thanks, and what exactly did you do to the shift fork to get it to clear? I hate this answer because it means the trany has to come back down when this was suposed to be a direct replacment
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Old Nov 9, 2004 | 08:21 PM
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You have two options, buy a different longer BH or take some material off of the back of the fork like I did, @ 1/4". WHrn you take the BH back off you will see the scratch marks on the back of the fork, make your grind spot/marks wider than that.

There is a guy on ebay with the 6.125 BH for $125 + shipping
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