mark kibort

wow.... I just looked a bunch of pics of wiring harnesses, scots, petty, my old cars.... all of them look brown.. they were red once? they all look like the classic Porsche brown wire color. If you say so..
as far as the solder, yes, I have a lot of experience soldering and while not optimal, I made sure there was a lot of solder in the key area of contact, and it went through a few layers of wire strands. a torch might have been too hot and weakened the metal at the joint...… leading me to more clarification … the loose wire didn't pull out of the lug, it broke off due to "fatigue".. so, the remaining wire that was not flexed near as much is safely pressed in the Lug, along with the part that broke off .(brown , aka 10mm red wire) with no compromise OTHER than its fatigue from bending over the many times of disassembly.

mark kibort

the video shows a couple of guys installing the super bearings at 12".... is that too far back compared to the 8" ive heard?

GregBBRD

The front bearing is very important, as the entire length of the clutch shaft, plus the 8" of the exposed torque tube shaft are unsupported by a bearing. There's a bearing at ~8" and then the tiny pilot bearing to support the other end of this entire shaft area, which includes the mass of the clutch disc and the mass of the coupler than connects the two shafts.

Things don't have to move very far or deteriorate very much, for there to be a significant "shake".

If the rear torque tube bearing migrates forward, the vibration/shake will very quickly ruin the splines on the torque tube shaft, the splines inside 5th gear, sometimes break off the "leaves" on 5th gear, ruin 5th gear bearing, and sometimes the transmission case.

Vibrations/shaking need to be investigated sooner than later.

GregBBRD

Constantine's specification is 10".

I'm not sure that there is a downside to 8".

12" seems like a long way back.....see my post above.

Bedfordman

gas pedal cable position
Out of the box thought on this vibration: Could it possibly be some resonance / fluctuation of the 'Gas pedal' cable?? ( Accelerator pedal cable to UK readers).

Mine was just looped over the top of the engine, some pictures seem to show it under the airbox.

I have passed mine thro' the air box clips as shown in the picture, gave me a smoother / lighter throttle control. I have never had the vibration you describe, but maybe airflow or some harmonic is causing your gas pedal cable to vibrate and micro change the throttle position causing this vibration??

probably a silly idea --- but it is a free option. Peter

mark kibort

no, I don't see how that could ever be an issue. when the cars throttle cable is at WOT, it is strained.... there is no chance of anything "vibrating" the vibration im feeling is a drivline or engine vibration . (most likely clutch or torque tube related)
you might need a new throttle cable for a lighter feel. routing it through the airbox is not really ideal.. there can be no "micro " anything with the the throttle plate. it just doesn't change the air that much even If it was vibrating. what I feel is DEEP in the driveline caused by the driveline itself or ignition related. ….. but much more likely to be unbalance in the driveline...……………...I have to dig in soon, now that we have some dry weather

Bedfordman

On reflection my comment may only be applicable to RHD cars, Peter

mark kibort

I was able to estimate the bearing position in the torque tube from the front of the torque tube.... its about 6-7" back. so, I don't think it is the same issue as mark. ive been testing it by running the car at near 5000rpm under no load, and there doesn't seem to be any vibration until I add a load. it can be at any speed, so that rules out all things but the drive line and first input stage of the transmission. it does feel oddly close to the vibration I felt when I was having issues with the throw out bearing (ring clip being ajar which allowed it to be mis aligned). the intermediate tabs are still locked in position at 1mm...…..
the vibration now still happens at 5000rpm, but continues to 6000rpm now too. not as noticeable at 6,000rpm but its still there. there is no other noises during normal driving. smooth as silk and very quite

mark kibort

Changed the trannie oil, and it looked good with nothing stuck to the magnets front and rear. good sign. it shifts like a dream still, even after 8 years of racing abuse. I have a feeling that its the clutch or throwout bearing. that vibration is very similar to when the ring clip holing the TOB became dislodged, effecting the balance. this time , it is NOT as bad, but still certainly not normal usually , the engine is smooth as silk to 6500rpm.... now, there is still a slight growling vibration about 5000rpm to 5500rpm, and it kind of goes away to redline, so its strange. im thinking it could also be a clutch disc failure. after all, GB said that Joe had a disc disintegrate when it had my power level with the stock clutch. also I think he had one fail at road America back when I was there with him in 2002. I hope I pull the covers and see something simple like the guide tube bolts have fallen out or something like that.

mark kibort

Well, I skipped the Laguna race in July because the vibration just seemed to be too substantial to ignore. SO, I got fired up and attacked the clutch removal just to see. nothing worse that doing a job where you are unsure if you are going to find anything wrong. anyway, pulled the clutch!! the discs still look almost new..... the pressure plate still had the TOB attached with the ring clip and nothing was disturbed (as was the cause when the clip was the issue a handful of years ago after a TOB replacement). the short shaft to TT coupler didn't pull back as easy as it usually did.. after clutch was pulled. TT shaft rotated without noise and was smooth. the bearing was only 5-6" back from the end . you could see that the front bearing had seemed to be pushed back a few mm , but not much. bolted it back together and it seemed to be much better, but still a slight vibration , but much more narrow range and much lower in intensity. I'm thinking it is within the acceptable range, but think that any imbalance is probably due to the TT itself. I made sure the clutch discs were offset by their balance mark positions...…

pilot bearing felt new. so, its all back together , with a slight fight..... my car, that was in that big crash at the track, bent the headers, so the toothed starter ring, barely fits and its a fight...… usually the entire clutch comes apart in your hands.. anyone that has done a clutch knows what I mean... so, I used a small dab of JB weld on a couple of the dowels to secure it as I assemble the clutch on the car. it works... must have done the clutch 3 times. 1st time forgot the support sleeve that holds the short shaft (UGGG) ...… 2nd time , I remembered it, but it fell off during the installation fight. 3rd time was charm after I added the jb weld to keep the clutch pack together during my rough installation . INT Plate still had the "pins" I installed 10 years ago and operating perfectly.

Next race, end of the month (Aug 2019) Laguna regional SCCA race GT2.class.

dr bob

Mark—

Check the rear bearing position too. Don’t know if you still have the torque tube damper in place. Make sure the rear bearing hasn’t moved back. Check for the plastic sleeve.

Check the harmonic balancer at the front of the crankshaft. If yours is original get one of Greg’s ATI replacements. Your statement about the vibration range changing and only significant under load points to imbalance at the driveshaft or failed front balancer.

mark kibort

Thanks! was thinking that too, especially since we are running out of options. Its slight, and could be my imagination, but I don't think it is. good idea to check the rear bearing position...…. what is the "torque tube damper"? I also was looking at the stock damper up front. kind of funny... what are you supposed to see, right? it looks fine... but heck, how do you test it??……. how do they fail??….that would be a nice and easy fix now wouldn't it , if it was the problem.

FredR

Mark,

Simple version: The engine damper is a lump of rubber spliced between metal plates- with time and heat exposure the rubber ages, hardens and thus stops doing its thing as designed and the energy intended to be absorbed goes elsewhere like into the front main bearing that GB reports seeing more and more pronounced failures. The stock dampers slips over the crankshaft- the item GB produces has a mounting hub that as I understand is an interference fit and thus transmits the energy into the damper more efficiently or so the theory goes. As and when i have the funds to spare this mod is high on my list of priority projects. The stock damper can also be rebuilt but how effective such work is I have no idea.

The torque tube damper is a static lump of metal that sits somewhere between the middle and rear bearings in the case of a manual transmission model [that has 3 bearings] - it is supported in rubber bushes similar to those the bearings sit in and they are known to go sloppy with the result that under breaking and acceleration they can swing backwards and forwards knocking the bearings out of position. I doubt that will have happened or you would have known about it given the clunk reported with such but...? Porsche fitted such after hearing "strange noises" in the rear of the cabin during prototype testing.

Rgds

Fred

dr bob

^^^ What Fred Said ^^^

The damper in the torque tube is there to kill a harmonic that happens are certain speeds. They are typically installed at a particular spot in the tube that's dependent on the frequency of the vibration in the tube. Excitation might come from either end, or via a bearing and carrier for the driveshaft. The need for them increases as the rubber supports for the bearings dry and harden, else they would do some of the dampening themselves. Constantine's carriers, in contrast, are larger and softer so there's a much better chance of killing the tube resonance, plus they transmit less driveshaft vibration to the tube too.

The damper on the front of the crankshaft is designed to prevent harmonics from breaking the crankshaft and destroying the main bearings. The crank twists with every compression and every firing stroke, in different places on the crank and different rotation points. The twisting and un-twisting test the torsional strength of the crank, and if you allow it to "ring" the added vibration will dramatically accelerate the fatigue failure. On the original damper, the rubber ring between the hub and what looks like the "timing ring" gets hard with age and heat, to the point there is no longer enough elasticity to actually kill the torsional vibrations adequately. With more power generated comes more and more torsional displacement, hence the recommendation to replace it when you see more vibration related to load increases. There are several good threads floating around on the subject.

Greg has spec'd slight interference fit on the hub he has made, vs. depending on a zero-clearance fit and the clamping available from the crank nose bolt. You can easily spot fretting on the crank nose when the fit isn't tight enough. Especially on high-output stroker engines like yours, a less than perfect fit will quickly ruin the crankshaft.

Torsional vibrations interrupt the buildup of an oil "dam" in the main bearings, and the additional movement will wear a bearing pretty quickly without that dam to lift the crank in the bearings. You can easily spot this kind of wear as it leaves a mottled wear pattern into the copper, vs. the more typical radial wear and smooth areas in the bottom bearing shells.

If you still have an original Porsche damper on the crank, get the correct replacement piece from Greg and call it good. No need to risk that race engine for something simple like this.

rjtw

Hi Dr Bob,
Not to hijack this thread, but for the rest of us with stock engines and original crank dampers, like my US ‘83 for instance with a much lower horsepower rating, is the damper something you would recommend be prophylactically replaced at this point in the absence of any other symptoms short of a teardown to examine bearings?
Cheers
Rick