Ok.. with my 360 LA bored stroked to 408 Internally balanced, I have picked up what im fairly certain is an engine RPM related vibration.
I thought after a high speed run that i had a driveline vibration, and pretty sure i did...but reworking the transmission (A518) to higher in the tunnel and adding a 2 1/2 degree shim to the rear axle i'm fairly sure i've corrected that. Last week with the entire car up on jack stands the rear supported under the axle, and using my cell phone camera to take movies of both the front and rear u-joints at speeds up to 75 (yeah...i was real nervous doing that) they both appear to be rock solid. So, fairly certain that's corrected.
But i still have a vibration. Driving the car at about 55 you can feel it in the seat of your pants and in the steering wheel... Not a sawing like would occur with tire out of balance but a buzzing feeling. So, began to notice that it is RPM related more than speed. .i.e at 55 when i engage the overdrive and then the locking torque converter dropping RPM to about 1700 the "buzzing type of vibration definitely is reduced to almost normal release both putting RPM back to around 2400 and you can definitely feel it !!
I thought what the heck and replaced the spark plugs with new ones, but that made no difference. Today i started to simply rev the engine slowly while parked and in neutral and starting at about 2400 RPM you can feel the vibration and at about 3500 its darn noticable...again...its almost like a vibrator that you can feel in the steering wheel and in seat of your pants.
Again, think maybe ignition i want to check each cylinder... so i used my infrared gun on each of the headers at full operating temperature i shot all 8. Here are the results...all farenheit cyl 1 about 480, 3 about 600-630, 5 510-530, 7 480-540
passenger bank... 2 380-410, 4 409-440, 6 455-570, 8 425-440 I think this proves all cyl are firing and the middle two on each bank definitely the hottest. While this was going on the outside temp here in NC was around 55 and the temp gauge in the car was showing low normal. I shot the thermostat neck and it was a solid 185 (180 thermostat in her).
Last time i checked the timing the static was at about 15-17 BTDC and the total was at 38 BTDC. I was going to check it again, but discovered that my timing marks on the Damper (SCAT unweighted) were missing. I guess their on with tape and it must have come off. Wonder if the damper is the problem???
Any suggestions what to check next ??
I had similar vibration issues, 360LA. I had checked the u-joints as they sat and they seemed fine. Chased my tail for a few weeks. Finally dropped the shaft and both seemed fine on the workbench as well. Lube was fine and no slop I could detect. I swapped them out anyway... vibration gone. Prolly the best $50 I spent last year other than the new house... lol.
GL!
-scoot
Thanks Scooter...but in this case pretty sure its the engine itself, as i can feel the vibration sitting still just by revving the engine in neutral.
^^^ In that case.. I'd double check timing, advance and retard it and see if there is any change to the frequency. If no, check that dampner.
My2c
I had a similar bad vibration on my 340/727 combo, and finally isolated it to the torque converter. This was on a 70 340, internally balanced. This was not an overdrive/lockup TC, though. Correct style torque converter and flex plate, but was 'generic' store brand from a popular on line parts store. I ended up installing a good name brand TC (that cost twice as much), and that cleared right it right up.
OK, lets back up a little. Has this vibration been there since the engine was new ? Diagnosis is a step by step process. Always start at the beginning and eliminate one thing at a time. Never assume that anything is ok just because it is new. Plenty of defective parts out there.
More detailed history would be good.
Quote from: MoparLeo on November 15, 2021, 11:05:19 PM
OK, lets back up a little. Has this vibration been there since the engine was new ? Diagnosis is a step by step process. Always start at the beginning and eliminate one thing at a time. Never assume that anything is ok just because it is new. Plenty of defective parts out there.
More detailed history would be good.
NO, when i first had this engine built, by a reputable close engine shop it was fine. It was built and INTERNALLY balanced using SCAT brand stroker crank. And a new SCAT brand damper for internal balance. Very smooth. At that time i was using a 904 transmission with a new torque converter for internal balance. It ran good but was worried the new horsepower was too much for the 904 plus i wanted overdrive.
Then i changed out the transmission putting in an A518 and a new Lock UP Torque converter for internal balance. It seemed to run pretty well for about 6 months, but, the first time i had a chance to drive the car on a fast highway I noticed a bouncing type of vibration at higher speeds. Starting at about 65 and taking it up to 80 it was a really bad bouncing type of vibration. SO i decided to check the drive line angles. Found them way off... Did a lot of work to get the A518 higher at the rear..which is difficult as not a lot of clearance, and then put in a shim at rear axle...
Still thought i had a drive line issue, so that is when i used my cell phone camera to record both U-joints with car on stands and running it up to 75. Locks rock solid..plus that vibration is way different then when the driveline was off.
Began to really pay attention to when it occurs and realized that it is RPM sensitive not speed. I.e at 55 it runs around 2200 rpm and that is when it starts, but, turn on the overdrive and LU dropping the RPMS to about 1500 and it is way less. Then noticed that just sitting in neutral and revving the engine slowly the vibration begins around 2400 and by 3500 RPM its i strong buzzing kind of vibration. So no longer thinking driveline.
After that is when i was going to check the timing and noticed the timing marks gone from the damper. I guess they had used a timing tape and it came off.
Ill try advancing and retarding it after i find the TDC mark and see if it makes any difference. I am also really thinking maybe all of the work to raise the transmission tail has "damaged" one of the engine mounts. I have the type of mount on drivers side that has the safety bolt thru it.
I've found solid, pinned and poly lock mounts do transfer a lot more engine vibration... good for troubleshooting if you are in tune with how your engine optimally runs.
If you are getting it sitting in neutral and revving the motor you can probably eliminate everything rearward of the flywheel.
That it ran fine before but just started notes something definitely changed or is failing.
Let us know what you come up with on the timing.
Obviously the vibration was not engine related if it changed only after the transmission/torque convertor was changed. That is why you don't just start to change several things at once and go back to what was changed or removed and replaced. What about the driveshaft ? Flex plate, torque converter ? Properly check the driveshaft angles ? Home made trans crossmember or professionally assembled unit ? Details matter.
https://www.therangerstation.com/tech_library/pinionangles.shtml
You didn't say how long you've been chasing this issue. I assume you've run multiple tanks of gas through the car since the issue first popped up? I had a very similar issue after the car sat over the winter.(with Sta-Bil in the gas) Engine vibration starting at around 2000rpm. It turned out to be bad gas.
Quote from: MoparLeo on November 16, 2021, 11:12:49 AM
Obviously the vibration was not engine related if it changed only after the transmission/torque convertor was changed. That is why you don't just start to change several things at once and go back to what was changed or removed and replaced. What about the driveshaft ? Flex plate, torque converter ? Properly check the driveshaft angles ? Home made trans crossmember or professionally assembled unit ? Details matter.
https://www.therangerstation.com/tech_library/pinionangles.shtml
Yes, the vibration probably started about the time i changed the 904 out and A518 in. However, you have NO CHOICE but to change several things when you go from 904 to A518. First the torque converter has to change as the 904 and 518 have different splines at the front. Yes, the transmission crossmember has to change as the A518 is a much bigger around unit, and NO there is no A518 in a Challenger off the shelf crossmember. So, i fabricated it myself. The yoke had to change because the spline count is different. The Driveshaft had to be shortened. I had that done at a professional shop and BALANCED...they also replaced the two U-joints with new ones. SO unfortunately that all has to be done at the same time as a system!!! No changing one at a time and going back !!
HOWEVER, i do believe that the vibration i felt at that time WAS driveline vibration as i didn't get the tail of the transmission high enough...a518 fit in the tunnel but lower do to its much larger diameter in the tail section. That is why i reworked the crossmember and the transmission mount to get it higher. Originally, i had about a 6 degree down angle. Now i have a 3 1/2 down angle (measured at the front crankshaft pully after the rework. The pinion with a shim about 2 1/2 degree up angle. That makes the front u-joint angle about 2 1/2 degrees and the rear about 1 1/2 up... So that the difference between the two is only 1 degree. This falls in line with the guide you listed.
BUT, i think i've had two DIFFERENT vibrations. The first was almost guaranteed to be driveline angle related and was speed related
.
I.e the faster i went the worse it got and it was a "bouncing" type of vibration. That is why i did all of the work to raise the back of the transmission higher.
Now, the vibration i get is
NOT speed related, but is RPM related and occurs with car sitting still and simply revving the engine...it gets pretty BUZZY at about 3000 and up. Thus i think along with the camera shots of the u-joints that it is no longer driveline but instead engine. So, what changed? Again, i'm thinking that the work i did with the A518 to raise its tail, either damaged the flexplate, or the engine mounts. Or maybe the engine vibration has been there for a while and i didnt notice it due to the driveline vibration. Hard to remember for sure.
Hmmmm. Everything smooth before 518 swap. Wasn't evident at lower speeds.
Driveline angles can certainly give you high speed vibration.
Have you shifted into neutral at highway speed just to 100% eliminate tires bearings etc?
You have ensured your driveline angles are correct? centre section pinion not loosened off a bit? (happened to me). Maybe output yoke of trans have some bearing play?
If all those other items are good...... Based on what you have entered as evidence, I'm thinking you may have a flex plate or torque converter crack/failure/out of balance issue.
Good luck. Vibration issues can be a bear to eliminate.
engine vibration in neutral means it is not drive line related. you have most likely got a bad converter/ broken flywheel or balancer /pulley issue.
:popcorn:
What do you know about the build ?
Was everything properly balanced inside ?
if you use a lighter piston without balancing for example the rotating assy inside could be the issue.
A customer bought a crate 360 years ago , I checked everything before installing it , there were numerous issues , cam was out 1 tooth for 1 .
I can't recall all the other issues but it was poorly built . after fixing obvious problems we installed it & the dash would bounce 2" at 2500-4000 rpm .
We had to pull hte engine tear it down completely & have it all balanced to fix it .
Not saying this is or is not the issue with yours . It could be just a bad converter / flex plate / damper problem , all external issues , but it will not be easy to eliminate those if it is the issue .
Chryco...It was professionally built and internally balanced (paid about $250 to have this done... when first installed it was very smooth... so this has definitely crept in.
Yesterday, i did compression test on 7 of the cylinders and all were in the 195 +- 5 range. Done while engine was warm but not hot... Throttle held wide open and two plugs at a time out. Couldn't get the compression tester screwed into the #7 cyl as the header prevents the compression tester with its host to go in straight...will try again today. But probably ok...
Also, going to try today to advance/retard static timing to see if that makes any difference. If not i think my next step (in order of simplicity) is to try replacing each spark plug wire...one at a time to see if it makes any difference.
Then next ill take the inspection plate off of the transmission (of course have to remove starter to do this), and try to visually inspect the flex plate and torque converter to see if anything obvious.. and of course make sure the torque converter bolts are tight.
After that will take off the engine mount to make sure it isn't broken. I hate to do that because i have to remove the header bolts and move the header to get out the main 4 1/2 inch bolt that secures the mount to the frame. Then ill probably have to replace the manifold gasket. Note: My mount i think i got from Mancini or maybe Schumaker has the safety bolt thru the rubber so that if the rubber breaks the bolt will still hold the engine in place.
My comment about making several changes was not about the conversion.
Obviously you have to change many things to do it. But making several changes at once when you are trying to chase down a problem.
Do you have access to a reputable garage That has a good tune-up tech ? They will have scanners, tools etc. that most people won't have at home and the expertise to find engine related problems quickly. It can cost a lot more in time and unneeded part replacement to try to find it yourself. Just an idea.
The suggestions that you get on these websites are generally from people who have had years of experience and access to a wide range of tools.
You can't buy experience but you can pay someone who has it.
If you are going ahead, then start with the engine. Recheck the tune. Don't fool with advance curves and such, just the basics first.
Pull and check all plugs, gaps etc.. Check inside distributor cap, rotor, that all wiring primary and secondary are clean and tight. Timing,
.
Just good basic inspections. Most problems are found to be simple things.
After you eliminate the engine vibration, then you can go after the drive line problem. Most likely loose or misaligned parts.
Verify everything is installed properly again, never assume. Good luck with your quest.[/font]
Decided to check my spark plug wires next. They are Mopar Performance Blue carbon graphite suppressor 8.0 mm wires. I have no idea what the ohms rating is supposed to be on these wires... I got readings of between 3500-3800 ohms per foot for each of them except ONE. That one read 330 ohms per foot. Looking at that one it is NOT the same wire as it is blue but with no markings on it, so not part of the original set. Could that much of an ohms difference cause the engine to be "slightly mis-firing" on that cylinder???
Anyone know what the older Mopar Performance 8.00 mm carbon graphite wires ohms rating is supposed to be ?
According to your readings, all the wires are bad. Should be closer to 150 Ohms per foot.
Quote from: MoparLeo on November 19, 2021, 02:12:52 PM
According to your readings, all the wires are bad. Should be closer to 150 Ohms per foot.
Sorry but that's not accurate. While some wires do have much lower ohms per foot the typical wires spec out pretty much at what he's seeing. Case in point the 1st set I pulled up states 3500ohms per foot. https://www.summitracing.com/parts/tay-70051
Quote from: MoparLeo on November 19, 2021, 02:12:52 PM
According to your readings, all the wires are bad. Should be closer to 150 Ohms per foot.
:dunno: Depends on the type of wires.
But, A misfire will not manifest itself as a consistent vibration. On again, off again variable maybe, but not what you describe.
"Typical" is subjective. I clicked on your link and the first wire I found had 50 ohms per foot....
"A wire with high resistance can be in the 5000 ohms per foot range for especially high-output ignition systems, whereas a low resistance performance wire could easily get double digit ohms per foot. Lower resistance means more of the ignition coils energy is going towards bridging the gap or the spark plug. " We are checking "Ohms" but did we already check the simple stuff ? The cap, rotor, connections etc.. more likely to cause misfires and rough running. Don't try to make simple things complicated.. K.I.S.S. look it up if you don't know what it signifies.
Last week i removed the transmission inspection plate... and inspected the flex plate and the torque converter and checked the bolts. All looked good...no cracks or anything of note.
So yesterday went the other direction and removed the harmonic balancer. It is a Scat brand for internal balanced engine (my engine was internally balanced when built). Nothing noticeable on it either... One thing that bothers me is that if you scribe a line from the keyway to the outside it lines up about 10 degrees to the RIGHT of the mark for TDC. Is this correct ? Or did it move on the elastomer ? Stated another way the TDC scribe mark is about 10 degrees counter clockwise from where the keyway points. This correct or a problem?
put a piston stop and a degree wheel on it. find true TDC on #1. Then compare the timing marks
Since you're still searching for answers, please take a look at this thread. It was more about noise than vibration and at a lower RPM, but just maybe....
https://forum.e-bodies.org/engine-transmission-and-rear-end/4/potential-causes-for-rattle-noise-as-my-340-approaches-3k-rpm-fixed/22987/msg275892#msg275892
Quote from: chargerdon on December 07, 2021, 06:24:06 AM
Last week i removed the transmission inspection plate... and inspected the flex plate and the torque converter and checked the bolts. All looked good...no cracks or anything of note.
So yesterday went the other direction and removed the harmonic balancer. It is a Scat brand for internal balanced engine (my engine was internally balanced when built). Nothing noticeable on it either... One thing that bothers me is that if you scribe a line from the keyway to the outside it lines up about 10 degrees to the RIGHT of the mark for TDC. Is this correct ? Or did it move on the elastomer ? Stated another way the TDC scribe mark is about 10 degrees counter clockwise from where the keyway points. This correct or a problem?
I don't know how it is for a small block like yours, but on the original damper for my 383, the keyway and TDC scribe mark are 90 degrees out of alignment. Maybe someone with a smallblock damper can chime in. Seems worth taking a closer look. Good luck.
Thanks... nobody has a small block damper on the shelf to look at ??
Quote from: chargerdon on December 07, 2021, 01:43:50 PM
Thanks... nobody has a small block damper on the shelf to look at ??
I did an image search for "small block Mopar damper" using Google, which came up with a number of pretty good photos. To me it kinda looked like the keyway and TDC scribe mark were in alignment, but 10 degrees isn't that much, so hard to tell for sure from the photos. You might get more traction if you start another thread asking if someone has a small block damper to look at. :alan2cents:
So at one time, you didn't have these issues and then after a while, they just started up?
When you feel the vibration at speed, can you let off the gas and coast, does it still feel the same?
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...
Quote from: 73_Cuda_4_Me on December 08, 2021, 05:57:34 AM
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...
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.
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.
8) 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.
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? :takealook:
It might be hard to start if TC is unbolted from flex plate...
:vipermanhiding:
Quote from: 73_Cuda_4_Me on January 10, 2022, 03:42:51 PM
It might be hard to start if TC is unbolted from flex plate...
It sure would be!
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. :bradsthumb:
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 !!
Nice find,
What is the trans angle now?