Resto Mod 1973 Barracuda round 2

[70chall440]

if your harmonic balancer is externally balanced and you have a 360, then you are good, but you need an externally balanced TC as well.

If you have a 340 and a harmonic balancer that is externally balanced, then it is wrong.

[redo1973]

Time for an update. It's been a month but I expected that.  We tried to figure out the issue sooner but my son the auto technician had his wedding and honeymoon so that delayed things. We have since done the following and once again some lessons learned.  I had a noticeable wobble in one wheel as the flange was bent but not the main cause of the vibration.  I've since replaced both axles with Mosers.  We sent the drive shaft out for evaluation.  Low and behold, it was bent, needed balancing and the slip yoke was pinching the U-Joint! I now regret not simply buying one but this is now like new.  All I can think of is that this car was in an accident.  There was clear damage on the rear driver side quarter when I bought the car but the extent of the damage looked like sheet metal.  Based on these recent discoveries, I'm now thinking was hit diagonally in the rear and caught the wheel as well.  We've run the car on stands and the pulsating vibration is gone.  There is still a vibration but one that is more related to "normal" mechanical/rotating that I feel is more familiar to the car I had in the 80's.  We'll do another shake down ride this weekend.

[redo1973]

BTW - I double checked my motor balancing.  My 340 motor is a February 1972 casting 2780930.  Per my research, Mopar switched to cast cranks for 1972/1973 which are typically not internally balanced.  I have a crank # 3462387 that fits the time-frame of casting per the charts on MyMopar.  I also confirmed through pictures I took during assembly that have a cast crank.  I installed an externally balanced Harmonic Balancer and Torque converter.  The motor does not shake at idle or higher RPM's although there is vibration through to the steering wheel.  I associate this level of vibration to be the rotating parts sending vibration through the stiffness I added to the K-Frame and urethane motor mounts.  Although I researched the balancing topic during the engine build, if I do a restoration again  , I'll pay more attention to this.  If not balance internally, would probably have elected a balanced flex plate over the converter and probably avoid the urethane mounts.  It appears that there are more part options for internally balanced motors.

[djw383]

How about the tires? Flat spots?

[70chall440]

An internally balanced engine requires a neutrally balanced harmonic dampener and TQ, these are sometimes called non-balanced or unbalanced. That said, if you had the wrong components on the engine, you would get a vibration relatively early in the RPM climb and it would get progressively worse.

Flat spots in the tires will be consistent and exhibit vibration early on and get more pronounced with an increase in speed.

So let's break this down, if you are getting a vibration through the steering wheel at idle, then it has to be a result of engine vibration transmitted through the K frame. That said, you are probably correct in that what you feel is normal. The steering column is rigidly mounted into the dash frame and any vibration in the car can be felt generally. So long as the vibration isnt horrible or violent you are probably good.

[redo1973]

Thanks Mike.   I put on some miles today and although there is a vibration, its most noticeable when I put it under load, like climbing a hill yet the car accelerates fine.  I would not consider this a "violent" vibration but annoying noise.  There is more like a drone from the exhaust.  To be honest, I don't remember what is "normal" and acceptable for these cars especially with the 2.5 inch exhaust and dynomax turbo mufflers.  Especially, since today's technology is so quiet and smooth.  The steering wheel shakes pretty good but settles in gear and with RPM.  My son is back tomorrow so we'll keep tracking but it is driveable. I'll let you know what we find out.

I've not heard of flat spots on radial tires.  How do I check that or are your referring to the biased tires?

[70chall440]

Yes radials get flat spots, the tires on my Viper are horrible about it. Takes a little driving for them to kind of even out.

Based on what you are saying in reference to the vibration under load, I would suggest you take a really hard look at your exhaust and where it runs. Are you running any type of torque strap on the engine. The vibration at idle and then under load has me thinking you have a bad or weak motor mount and it is being transmitted through the car, additionally when you are under load it is causing the engine to pull the exhaust up and hit something solid which can feel like a vibration. Just for fun, rig up a simple chain on the drivers side, bolt one end to the engine and the other to the frame. You want it to be tight. then drive it again and see.

[redo1973]

I think that you are onto something.  I have the two brackets, probably 1/8 thick angle style that I've not determined how they mount.  I was thinking it to be some bracing between motor and transmission but haven't figured it out. I also have new motor mounts but will check tightness.  Sounds like today's task.  It's raining here on the east coast so I guess no yard chores today and I'll have to stay inside 

[70chall440]

Post a pic of the brackets, they sound like the original trans to motor support brackets (kind of twisted, about 6-8" long)? Those brackets were usually tossed the first time the engine or trans came out of the car. Not saying they aren't useful but I've never run them on a modified car and have never seen any on a race car; in other words those brackets are not a contributing factor to your vibration.

Give the torque strap deal a try and see if that makes a difference.

[redo1973]

I don't know where time goes.  Here is a picture of those brackets.  As for the vibration, it seems to have minimized to a motor vibration that changes with RPM and then the exhaust drone.  We'll probably change over to rubber motor mounts over the winter.   

[70chall440]

Yes, those brackets were used to connect the engine to the trans at one time.

[redo1973]

Hello all, I wish that I had good news on my Cuda's show performance but not yet.  My wife and I had some misfortune in September when we suffered a garage fire.  Fortunately my five year project was not a victim of the situation but it has certainly put a distraction in my journey.  Here are a few pictures of the shows I attended post fire. I still have some interior work and water temperature leaks but is running much better now that it is over 700 miles.  It is certainly an attention grabber.

As you all know these projects are never complete but mine is at a point that I can hang my head high and wanted to take a moment to share a thank you. I am so glad that 4 Cruisin connected me to this site.  There are so many folks here that volunteered their knowledge, support or simply show interest in my journey.  I think that knowing someone is interested in what and how you did somthing is so rewarding.  70Chall440, I can't thank you enough for the regular motivational feedback, moral and technical support.  Your project has been highly motivating and I wish you success on its completion.   I'll do my best to stay active here and continue sharing my experiences but this winter's attention is restoring the house. The Cuda is in storage and I'll get back to it when garage space becomes available.

Thanks again and I wish all of you the pride that comes with saying you restored that car.  FYI - that Challenger is a Hemi and was my only e-body competition at the show

[redo1973]

resized the picture.  BTW - ther were over 1,000 cars at that show.

[70chall440]

redo1973,

That car looks absolutely amazing! That blue is stunning and I bet even better in person. I am very glad that my own efforts and comments were helpful to you. I am very close to being done with my car, thank you.

A huge CONGRATULATIONS!!!! I know it feels great and if you are like me you are smiling like a little kid at Christmas every time you drive it.

[redo1973]

Well it's been quite a while but we've been back in the house for several months and finally able to put time on the cuda, without guilt.  My son's been tuning the carburetor and it began to smooth out a bit.  The biggest revelation was the Harmonic balancer.  The motor is externally balanced and when I bought the balancer my expectation was it was correct.  Well, another learning point, that balancing was way off. It had 12.5 ounces and we only needed around 3.5 .  A quick test with stick-on wheel weights proved the theory.  It ran much smoother with limited drone at any speed.  We'll be putting on a new balancer this weekend!  Next hopes is no damage to the rear main or elsewhere.