Still working on the shake at launch issue I have with my stock 69 Barracuda Formula S 383 4 speed car. Just a question concerning the bell housing. If the Parallelism of the tranny mounting surface or the concentricity to the crankshaft were out of spec. would that cause an intermittent hard shake at standstill take off? Once the car is rolling it's fine. No shifting issues. Just take off shake.

I've done lots of work on this car the past 2 years and still trying to pinpoint this issue. All the obvious stuff and then some. Thinking more out of the box at this point.

Thanks.

Alignment out will cause high rpm vibration. Sounds like clutch chatter to me. I'd check the surfaces if your clutch and pressure plate. Also the disc needs to have good springs and attached to the steel in a way that it has some space in between the two disc. I had a racing disc with solid backing on the material and it would shake terribly. I think it's called the marcell that it's attached to and it is cupped so it acts like a spring or cushion. My best guess.

Here is what I've done so far:

New Mcleod clutch/pressure plate set & throw out bearing from Brewer's.
New super stock springs and bushings.
New pilot bushing.
New tranny front bearing/seal. Ensured tranny shaft didn't have burrs or imperfections.
Resurfaced/ measured pressure plate twice during the removal and re-inspection of the new clutch components.
New rear tranny/motor mount.
Adjustable pinion snubber.
Measured pinion angle. 2.5 degrees negative. Also played around with 2 and 4 degree shims to make more negative.
Ensured correct drive shaft length.
Thoroughly inspected the linkage, 3 times.
Checked the motor mounts. They appear like new. Motor does not move a bunch during hard launch. Also looked at them with the emergency brake set and clutch release to load the motor.

I'm probably missing something but this is most of it. Car does not vibrate at all going down the road. At a rolling start does not shake. Standing still however during light or hard launch you get some degree of shake. I can actually get a violent shake at light launch. Shake that is way more than any clutch chatter I've ran into over the years.

I have added traction bars to it and set the snubbers against the springs. You can drive it with very little to no shake at launch that way. I don't like doing that but it at least allows me to drive the car.

When you say "resurface" in the above statement are you referring to the flywheel or pressure plate ?? And how did you resurface them. I have heard of flywheels developing hard spots from heat that cannot be corrected by surfacing. Your description sure sounds like a clutch, PP, FW issue.

I was referring to the flywheel concerning the resurface. The PP is new. Can the hard spot areas be identified prior to resurfacing?

Where does the shake feel like it's coming from? Back of the car, middle? What type of tire is on the car?
The reason I ask, is I had a similar situation when I swapped tires on my car. I went from a drag radial to a bias ply and had horrible tire shake on a hard launch.

What type of shocks too?

I replaced the shocks all round and have the longer units in the rear to accommodate the super stock springs.

shake feels all over but mostly in the middle. I've got 15" Mastercraft 50's on it now but it also shook with 14" BF Goodrich TA's. Both street radials.

To my knowledge without testing, No. Before the surfacing they visually appear as blued or other color irregularly shaped spots and sometimes cracks. After surfacing the surface may appear fresh and normal but can be very irregular to a friction surface (clutch material). Most clutch manufacturers typically recommend a new flywheel for the above reason.

So to be clear, the flywheel could have hard spots due to overheating that resurfacing can hide. I guess I should pull that back apart and look at the flywheel now after driving the car around for almost a year this way. It may tell me something now where it wouldn't before. The car had been sitting for quite some time and may have been shaking on the previous owner.

Launch issue, what do you mean by launch? Are you talking about a shudder if you feather the clutch from a standstill or a shudder if you "dump" it from a standstill?

read the earlier posts, it does both

keep us posted on what you find.
Myself, I might just put an entire new assembly and flywheel in.
FYI We have had very good luck with the Centerforce dual friction clutches in our own as well as customers cars

Sounds like clutch related vibration, chatter
Did you possibly get some oil or other oil based liquids on either the clutch disc, pressure plate or flywheel?
If so that may be part of the problem

What type of material is the disc face have on it? Certain High Performance materials will grab causing your shutter condition. If it's a stock type rag facing look for broken or weak mounts ,sing bushings or bad shocks

Both.

I've had the Assy. apart twice looking for those things. Non found.

The Hays setup I took out really didn't look all that bad considering all the shake. I put in this McLeod setup based on Wayne Brewers recommendation. This same setup worked great in my 68 Bee a few years ago. Shake the same before and after.

I am considering a new flywheel. I got to get it back apart anyhow but hate to just keep throwing money at it.

You can try this to eliminate some of the components as contributing to the problem.

Replace the driver's side engine mount with a solid mount, or drill a hole through it and bolt a nut with washers through it and or chain the motor down so it can't lift up any more than 1/2".

This will hold the engine from being able to lift from the torque. I've had issues in the past like this. using a solid mount eliminated the changing geometry of my linkage when the engine moved and pointed me in the direction of the aforementioned missing Marcel spring that cushions the grabbing force of the clutch.

Rigid puck style clutches don't typically have Marcel springs and they tend to chatter unless they are essentially dumped at the starting line or the engine trans is solidly mounted. I still have some of those old solid puck clutches laying around.

It wasn't until the Mcloed Street Twin's came out that I was able to have a clutch live on the street with a high output engine with no chatter.

Reading through your struggles and BELIEVE me I've BTDT, I'm wondering if the flywheel has not been the culprit all along
Especially if it has not been replaced. Other than replacing everything, The only other option I can think of is to send the entire assembly into the current supplier (McLeod) for analysis. just my

Silly though just occurred, So one other stupid question ?? any chance the crank has too much end play??

please keep us posted