new member //1st vette//please help.

[zbest4me]

Please help. This is what I have:94 torch red vette LT1 w/ 6 speed manual transmission. Engine upgraded to a 383 CID, 3.750 Stroke Crank, 4.030 Bore, 5.7 Inch I Beam Rods, Fully Ported Cylinder Heads and Intake, Ford Motor Sports #30 LB Injectors, 52 MM Throttle Body with Air Foil, 1.6 Ratio Aluminum Roller Rocker Arms, Hokker Long Tube, 1 3/4" Ceramic Coated Headers, MSD Digital 6 Box. 420 HP



Now here's the problem: I have a "fresh" factory dual-mass flywheel with factory clutch in there now. I get serious vibration anything over 3,000 rpm. I have been told that I might need to take the Stock flywheel out and have it balanced so it is O-balanced to match the crank. I've already invested about $1600 parts & labor trying to figure this out...I need to know what to do next. thanks in advance for any help on this. If not anyone wanna buy this thing?

 

[jmccloud]

Vibration

Did it vibrate before putting in the flywheel? Or was all the work done at the same time?
If the flywheel installation was done most recently and no vibration before, I'd suspect that a drive shaft u-joint cap/retainer wasn't installed correctly. A small piece of crud or dirt under the yoke or retainer strap will raise havoc with vibration. Either joint (behind the trans or in front of the rear) would cause the same vibration. If a needle bearing was lost out of one of the u-joint caps, it can cause exactly the vibration that you describe.
Trouble shoot this by 'measuring' (feeling) the vibration at 3000rpm in various gears while driving. If it's always the same at 3000rpm, focus on the clutch. If it changes with the gear, suspect the u-joint.
The vibration damper on the front of the crank should be included in your diagnosis if it was changed between the before (no vibration) and after (vibrates now) conditions.
Hope this helps,
Smooth riding

 

[zbest4me]

Here's the kicker... It does it in neutral or rolling. clutch in or clutch out.

 

[taegdh]

If your clutch and flywheel are balanced, check the other end of the crank shaft, your harmonic balancer may be causing disharmoy with the rotating mass.

 

[zbest4me]

does anyone suggest a "fix-all" type balancer for this application? The flywheel is now balanced to -0-.

 

[kenwa]

It's the Ford injectors.

 

[zbest4me]

It's the Ford injectors.

:L I bet your right. out of all the things that was done to this thing the one thing that blew my mind was just that!

 

[kenwa]

Welcome to CAC!

 

[Moonunit 451]

Lots of folks swear by those FMS injectors, wish I could help on your problem. Be patient someone will. WELCOME

 

[zbest4me]

Thanks for the welcome to CAC.

another quick question. my idle is a steady 1100 rpm cold or hot. is that not a bit too high for a 383? or does the cam have something to do with it?

 

[Moonunit 451]

To high, check the IAC, there is a very specific procedure best done with a computer but can be done with a multimeter. Why not give some more specifics about your setup? MR, SR, Cam, TB ect.? That would help. But The IAC or a vacuum leak is where I'd start.

 

[SPANISHVETTS]

Is the crank internally or externally balanced? The flexplate, flywheel and trosional damper are different. Mixing one with the other will cause enough vibration to shake the beast apart!

 

[zbest4me]

Is the crank internally or externally balanced? The flexplate, flywheel and trosional damper are different. Mixing one with the other will cause enough vibration to shake the beast apart!

thanks, the crank is internally balanced. the dual mass just got balanced to neutral. the damper is stock without any inserts into the holes.

 

[SPANISHVETTS]

thanks, the crank is internally balanced. the dual mass just got balanced to neutral. the damper is stock without any inserts into the holes.

I think you have pinpointed your problem. Starting around ´86 all SBCs are also externally balanced and require a specific flywheel and flexplate. You do not see the balance holes in the damper because it is balanced with weights on the inside. To quote Lingenfelter;worship , ¨the engine will suffer a sever imbalance condition that will shake it right out of the engine compartment!¨