engine vibration...where to look ?

[chargerdon]

Just checked my spare 340 externally balanced damper with a degree wheel, and the crank keyway is 10 degrees clockwise to the TDC timing mark...

Thank you sir... so nothing wrong with mine...   So will be putting it back on...   

Not sure where to look next... 

[dodj]

Well, with what I've read...I'd be looking at replacing the torque converter. But I would also research torque converters a little more because I wouldn't want to drop the trans without a little more backup to my thoughts.

[chargerdon]

Ok...i've eliminated nearly everything that i could.  Again this is on my 360LA engine with SCAT stroker kit to 408 internally balanced engine that when torque converter is a high stall (2200+ RPM Stall) torque converter with lock up.

List of things ive tried:
1) replaced the spark plugs...no change
2) replaced each spark plug wire with a spare, one at a time and checked that the vibration remained.  So not a plug wire.
3) Checked compression of each cylinder except #7 which i cant get the compression checker hose into without removing the header and their all the same.   Also, used an infrared temp checker on each header pipe at idle ant their all read in the 450-550 degree range..so their all firing. 
4) put in spare ECU (electronic ignition) and no difference.
5) replaced the coil with a spare and no difference
6) Vibration is definitely engine rpm sensitive starting at about 1800 rpm and increasing to its worst at about 2500, and this occurs both when driving the car or just revving it in either neutral or park ...A518 automatic.
7) Removed the damper its a SCAT brand neutral balance and i see no signs of it "giving" and the TDC timing mark is about 10 degrees before the keyway spot like its supposed to be. 
Ran the engine with the fan and power steering belts removed to insure none of those is causing the problem.
9) Removed the inspection cover on transmission and visually inspected the flex plate, torque converter bolts, and the torque converter in general...  all "LOOKS" ok.   Bolts tight.   

10) Havent done it yet but, i guess replacing the distributor cap and rotor would be the next thing to try.   

I HATE the thought of replacing the torque convertor as next step as its a lot of work, and expense.   Any further definite steps i can take to know for sure if its the converter ???????   

PS...on a scale of 1 to 10 for severity i would say this vibration is about a 3.   

[ek3]

un-bolt the converter from the flywheel. it will be smooth if the converter is bad.  as i said before ,i think its the converter... or flywheel is broken? 

[73_Cuda_4_Me]

It might be hard to start if TC is unbolted from flex plate...

[dodj]

 

It might be hard to start if TC is unbolted from flex plate...

It sure would be!

[ek3]

i dont know where you guys get your info from. i have a 600 hp 14-1 comp. ratio engine that uses a bert trans with nothing but a hub and a thin automatic transmission flywheel. it has never failed. 

[chargerdon]

Well i finally found about 80-90% of the vibration.   

Started to really think about when i noticed it originally, and finally realized it was when i was trying to raise the tail of the transmission higher...that A518 fits in there pretty tight and i have about a 5 degree down tilt at the u-joint to driveshaft angle.   It is a homemade transmission cross member (A518 transmission) and i had stuck a piece of hard rubber under the place where the GM style mount meets the transmission cross member to raise it a little higher.   Removed that piece and that seemed to cure 90% of the engine vibration. 

However, now i think i'm back to having a slight driveline vibration, so i'm going to try to raise the rear pinion angle upward to match the front by putting in the 2 degree axle shims in front of the axle.  Right now i'm driving it without any shims.   

Wow...Has this been an interesting journey !!

[Katfish]

Nice find,
What is the trans angle now?