Vibration after open track with FFR

mj_duell · #1 (**permalink**) 10-22-2007, 12:31 PM

Quote:

Originally Posted by CobraEd

I would check the ring on the harmonic dampner behind the front pully just to be sure. If it is loose, it will cause very bad vibrations that change with the RPM.
.

I'll check that out as well. I was wondering.... I beat the car up pretty good all day, what are the odds the clutch cable may need adjustment or repair? Could it be hanging up the clutch slightly and causing chatter? I didn't think of this before because I do not see any slip when I'm on the gas.

--Mike

DAVID GAGNARD · #2 (**permalink**) 10-22-2007, 02:35 PM

Mike;

If the vibration stops when the clutch pedal is depressed and the clutch is dis-engaged from the pressure plate, I would have to think it is the clutch itself, or the pressure plate........outside chance it could be a problem with the flywheel.....

I would pull the trans and check this out before running the car much more.vibrations don't usually go away on their own and can and do lead to other problems down the line....if the vibration is severe enough, it will eventually cause other things to work their way lose and cause more problems...

also, check out the pilot bearing in the end of the crank while you have things apart.....

My guess, is the clutch disc itself may have lost some of it's material and throwing things out of balance, just my hunch.....

David

mj_duell · #3 (**permalink**) 10-22-2007, 07:15 PM

Quote:

Originally Posted by DAVID GAGNARD

Mike;

If the vibration stops when the clutch pedal is depressed and the clutch is dis-engaged from the pressure plate, I would have to think it is the clutch itself, or the pressure plate........outside chance it could be a problem with the flywheel.....

I would pull the trans and check this out before running the car much more.vibrations don't usually go away on their own and can and do lead to other problems down the line....if the vibration is severe enough, it will eventually cause other things to work their way lose and cause more problems...

also, check out the pilot bearing in the end of the crank while you have things apart.....

My guess, is the clutch disc itself may have lost some of it's material and throwing things out of balance, just my hunch.....

David

Hi David,
I was afraid someone would say that. Tonight I checked the balancer, driveshaft, engine mounts and tranny mount as well as clearances. Nothing wrong. That seems to leave me with the inevitable.

One thing I did find during my search is that I have lost a header bolt on the driver’s side and a few others were loose. I was unable to fire up the engine to see if that had any effect because of the time. I’ll give it a check tomorrow. I have sworn off any new thrashings of the car until I get the problem fixed.

Thanks,

Mike

DAVID GAGNARD · #4 (**permalink**) 10-23-2007, 04:04 AM

Mike;

Loose header bolts,especially on aluminum heads is very common......I've lost track of how many came out on my car......that should not have any effect,except maybe blowing a header gasket now and then....Usually after every two or three track sessions,once the car cools down,I run a wrench on all the header bolts,after two or three times doing that you should be o-k, but keep checking them......

I've seen some clutch disc's loose a piece of material before, sometimes a pretty good size chunk can come off and then it will throw things out of wack, also,if your pressure plate is the type with the weights on the "fingers", you could have lost one or more of the weights and that will definetly throw things out of balance...

I know it's a pain to pull it down, but it's better to do that then have something else vibrate loose and tear up.......

At least you did not find pieces of oil rings on your oil drain plug like I did this weekend!!!!!!!!!!!!!!

One thing I've found out is that track time on a car is about equal to 10 times that amount of mileage on the street or MORE.......I spend at least one hour checking things on the race car before hitting the track each time just to make sure everything is tight and in good working order............

David

mj_duell · #5 (**permalink**) 10-23-2007, 04:44 AM

Hi David,
Yup. I know I'm headed for a tranny removal. No big deal just time consuming. I have seen cars that have never leaked or made any noise suddenly start spraying oil and back fire when I tracked them. You are correct, the track does take it's toll.......I'd never stop doing it though

I always check things out before track time and between runs. I lost a couple lugs at WGI and was lucky enough to make it back to the garages. I had tightened them down before my first run that day. Taught me a very valuable lesson about checking the car every time!

I'll keep you up to date on the clutch. I won't have time to get to it until this coming weekend.

"At least you did not find pieces of oil rings on your oil drain plug like I did this weekend!!!!!!!!!!!!!!"

Bummer! Never a good sign. Let me know what you find.

--Mike

carmine · #6 (**permalink**) 10-23-2007, 06:27 AM

Mike; does the vibration go away or become less as your rpms go above aprox 2400 rpm.

mj_duell · #7 (**permalink**) 10-23-2007, 06:38 AM

Quote:

Originally Posted by carmine

Mike; does the vibration go away or become less as your rpms go above aprox 2400 rpm.

No, but I wish it would.

It does seem to level off a bit when the rpm's get high enough.....maybe around 3000 or so. It's really driving me nuts. I will figure it out in the end, but I believe I'm in for a long search. If I had to describe the vibration, I would say that it is not present at idle. It builds starting just slightly on throttle and is pitched with the RPM's. The engine vibration is not noticeable by eye, but is definitely coming from the engine, accessories or bellhousing area. The engine performance is normal with a steady idle, no back-fires, rough idle, stumbling etc. It almost feels like the timing is off if you know what I mean. Something is not balanced or the adjustment is off.

--Mike

John McMahon · #8 (**permalink**) 10-23-2007, 06:37 AM

Mike,

Its easy to see why you may not have seen the missing header bolts!

mj_duell · #9 (**permalink**) 10-23-2007, 06:45 AM

Quote:

Originally Posted by John McMahon

Mike,

Its easy to see why you may not have seen the missing header bolts!

I knew that pic would turn up eventually

. Maybe I need to put those glasses back on and the problem will show itself! That was a fun event, can't wait until next year!

--Mike

JCoop · #10 (**permalink**) 10-24-2007, 09:45 AM

Motor mounts cracked or broken...just a thought...

RICK LAKE · #11 (**permalink**) 10-24-2007, 11:49 AM

Carmine What dampener is on the motor? Stock, ATI, Any markings? I will still go with the clutch assembly. Pulling the trans and clutch itself would be the first place to try and locate the vibration. It could be a bad bearing in the water pump, pulley not spinning true on the crank, If this problem just started I would stay with the clutch and flywheel first. Rick L.

JCoop · #12 (**permalink**) 10-24-2007, 12:26 PM

The reason I thought motor mounts is because for the longest time, my SPF BB would break the RH sidepipe mounts and vibrate at around that same RPM; whether driving in gear or in neutral at rest. The 3rd time I welded the mounts, I decided to change the motor mounts to poly (from Dennis O.) and haven't had a problem since. Didn't even realize it but the original rubber mounts were cracked from "spirited" revving and driving.

Worth a check, anyway. Cheers and good luck!

carmine · #13 (**permalink**) 10-24-2007, 12:44 PM

Interesting what you mention about the mounts, had that same problem with the right side, then changed to poly mounts from Olthoffs but vibration still there. What do you mean by you ( welded the mounts ). regards Carmine

JCoop · #14 (**permalink**) 10-25-2007, 06:07 AM

Quote:

Originally Posted by carmine

Interesting what you mention about the mounts, had that same problem with the right side, then changed to poly mounts from Olthoffs but vibration still there. What do you mean by you ( welded the mounts ). regards Carmine

I welded the broken piece on the sidepipe mount, then I bent a cut piece of .5" round steel rod to the same angle as the sidepipe mount, then welded that to the underside of the mount to reinforce it. Ground it down to finish it and painted it hi temp black. Make sure you use a welding blanket to protect the door and sill paint...

Actually, the new mounts transmit more of the engine resonance now than it did before. It's throughout the entire range, however. I feel it more on the seatback and can get annoying on a long drive. It got rid of a drone I had between 2400 and 3500, though. I suspect that was the broken motor mount. I guess it's a trade off for the crispier feel and seemingly more immediate response I get.