How to balance an Engine?

[Challenger_7]

Hi all
This should be either a challenging question or one impossible to deal with
Few weeks back I bought my third 71 Challenger with a 400 souped up engine and slap stick, see photo. I was thrilled by the purchase as the car has awesome power.
Quite a few things needed attention such as hard shifting, misfiring plugs, bad idling etc whcih I assumed will be easy to deal with. Some were, but when I got to the gearbox, we discovered it leaking oil. After stripping it, we found extensive damage in the gears, pump and torque converter, all of which were changed.
The core of the problem turned out to be a badly vibrating engine which led to wear on the neck of the torque converter thus leaking oil and some driving without oil leading to burning of clutch plates.
Now having changed everything, the mechanic is trying desparately to balance the engine because he said if left like this, it will wear out the torque converter's neck again and lead to the same destruction. The way he is doing it is by welding on some weights to the surface of the converter, as sometimes is the case fom the factory, and see if it helps.
So far he managed to reduce the vibration, but it is still bad, and he is still trying by "trial and error" method. I asked around if there are any shops that deal with this but found nothing.
What can you Gurus suggest ? Please help me save my car 

[firefighter3931]

Nice car....looks great in the pics. 

Ok, onto the balance issue : a 400 engine is externally balanced. That requires the proper harmonic balancer on the front and weighted torque converter for the balance to be properly maintained. The first thing you need to do is make sure you have the correct harmonic balancer on that engine. The cast crank dampner is approx 2in thick and that is what you should have on there. If the tq converter is neutral balance and has no weights you need to purchase a weighted tq converter or a flexplate that is designed for a cast crank engine and neutral balance torque converter. B&M makes that exact part for those types of applications. 

Basicly, you need to do a little research to see what's on that car; first thing is to check the harmonic balancer to make sure it's correct. Second thing is to check the torque converter to see if it's neutral balance or has weights welded on. From your description it sounds like a neutral balance converter. That being the case, a simple flexplate swap will solve the problem. 



Ron

[Challenger_7]

Wow !!! Thank you Ron
I will certainly sleep better tonight, and thanks for the compliment
Ok on the balancing issue, I will check for the harmonic balancer tomorrow. It is visible without opening up the engine, right? It fits just before the pulleys on the crank?
As for the converter, it came balanced with roughly 15-20 grams. The mechanic took this off and the vibration became worse, so he welded new ones on, and will be trying to add more on tomorrow.
You say B&M supply flexplate. What is this, and how do I use this? Also in view of the fact that the converter has weights, do I still need the flexplate?
Also please keep in mind that the 400 engine is not standard any more and has been souped up. So only God knows what the previous owners have done to it, and I have no contact with the owners that have souped up the engine. So the question of balanced 400 engine, to me is in question. Right?

[firefighter3931]

Yes, engine balance could be an issue. I would start off by making sure that the correct balancer is on there. 

Here's a pic of the 2 styles of balancer.....the thicker one is what a cast crank 400 engine should have on it. 

The tq converter weights need to be in the correct location for the balance to be spot-on. I would remove the weights and verify neutral balance on the converter....then order the B&M flexplate that is correct for the application.  Here is the B&M plate that is needed for a neutral balance converter with an external balance engine. There is a scallop cut out of the plate that compensates for the balance issue when parts are mismatched.

http://store.summitracing.com/partdetail.asp?part=BMM%2D10237&N=700+4294925134+4294839071+4294863762+4294908078+400004+4294840135+4294925079+4294871900+115&autoview=sku

* the image in the link shows 3 flexplates....the bottom one has the scallop cut-out and is correct for the neutral balance converter/cast crank combination.



Ron

[Challenger_7]

Ok Ron, I logged onto the B&M site and this is the photo of what they are offering. The kit includes all 3 discs or do I choose from them?
And whats with the toothed one? Is that a replacement for my flywheel teeth?

[firefighter3931]

That photo show's several different flexplates/flywheels. The toothed wheel is for a GM vehicle. Why they don't just show the correct part (alone) i don't know ?  The bottom flexplate is the correct one for a cast crank/neutral balance converter assembly.  When the part is ordered you will recieve only one flexplate. 


Ron

[kamkuda]

Did you determine if you have the correct balancer.  I may a spare if you need one.   BTW, nice car!

Rob

[tecmopar]

As Ron said, check the dampener first before you go any further with the converter issue. Its been a while since I played with these "later" motors but I seem to remember the damp/balancer having an offset weight on it and stamped " for cast crank only", good luck.

[Challenger_7]

Ok comments noted with thanks.

I will be going over to the mechanic today and will check the car out to see if the damper is there. Will take some photos if I can.

Rob, thanks a bunch too for the offer. I live in Lebanon and sending that thing from there might cost a lot. In case I need one, I feel I can get it here, but if not, I will sure take you up.

Thanks.

[Challenger_7]

Ok here we are again. Went to the mech who had parked the car outside, almost froze to death, but here I am
I could barely reach from the top for a reasonable picture but I managed to catch part of the damper. So it looks like I am ok there?? Please see Pic.
As for the Torque Converter, this is a photo of the old one, which had no weights. Also pls see pic. Now if you look at the screw on the upper right hand, approx 2 o'clock, the mech said that the new one came with 2 weights welded, each one approx one inch from each side of this screw.
As for the plate that connects the engine to the converter, he said it is square in shape, and not round like the one from B&M.
So from what Ron said, do I replace the old plate with the one from B&M, AND take away the weights on the new converter, or keep the weights?
Another thing, is there a specific way to mount the flexplate, i.e. where should the cut-out part be?
Another thing from an engineering point of view, how can this plate, with a missing part in it (so to speak) "determine" how much off-balance the engine is, and eliminate that imbalance?? I dont get it
Thanks again for your input. I will be away from my computer till Tuesday, and wish all of you the best for the year to come, to you and all your loved ones, full of love, prosperity and peace.

Farouk

[firefighter3931]

Farouk, those pics help clear up some questions we had. 

(1) You have the correct harmonic balancer on that engine which is good news.
(2) The original TQ converter that is pictured is for a neutral balance engine.....this was causing your vibration issues.

The new converter is supposedly for an external balance engine but the weight could possibly be in the incorrect location.

If it were mine: I'd knock the weights off and use the B&M flexplate with the new converter. The converter will only bolt up to the flexplate one way....the bolt pattern is assymetrical. That means that the scallop (cut out) is in the correct location to create the external balance. Since the converter can only be bolted on one way....you can't go wrong.  This will be obvious to whoever is installing the flexplate....the converter will have to be moved around until all 4 bolts line up with the holes in the flexplate. 



Ron



Ps. I would have the mechanic verify that the Tq converter is in fact neutral balanced (after removing the weights) before re-installing it in the car with the B&M flexplate.

[Steve P.]

I like to paint on alignment marks on both the flex plate and the converter before final install. That makes it real easy to line the bolt hole up without having to spin the converter around. The tranny will be out for the job anyway, why not??

[Challenger_7]

Happy new year guys, and hope your year ended with a blast

Thanks Ron and Steve for the useful comments.

Ron, some more questions from me, and please bear with me as I am new to challengers (and muscle cars), and some questions are for my benefit and not so much the mechanic's.
I am an auto engineer, graduated from England (UK), but spent most of my years (and still) taking care of family business, so many times I am very much in a "back to the drawing board" situation, and have little opportunity to do stuff personally
Also being somewhat close to a "perfectionist", I always want to be sure to understand issues perfectly in order to make sure that my mechanic performs a correct job. I follow every bit of work very meticulously, and take tons of pics for records and follow up purposes.

Now to my questions:
1. To make sure I understand this well, the flex plate from B&M will replace the original plate?
2. Is the original plate also called a flex plate?
3. What is the meaning of "neutral balanced" and how would I check it out?

Thanks again, Farouk

[Challenger_7]

Ron, one more help needed.

I just logged on to the B&M site to order the flex plate, and when I clicked on it to be added to my cart, it showed the following description
"Flexplate, External Balance, 2-Piece Rear Main Seal, SFI 29.1, 6-Bolt, Chrysler, B/RB, 727, Each ".
I am confused by the word "2-Piece". Is this describing the rear main seal as 2-peice or is it referring to the flexplate?
In short, am I ordering the correct part?

Thanks buddy.

PS. Would appreciate some comments on the "engine colors" post which I made today, if you wish.

[firefighter3931]

Now to my questions:
1. To make sure I understand this well, the flex plate from B&M will replace the original plate?
2. Is the original plate also called a flex plate?
3. What is the meaning of "neutral balanced" and how would I check it out?

Thanks again, Farouk

Happy new year to you as well Farouk !

To answer your questions:

(1) Yes, the B&M flexplate will replace your original.
(2) the original plate is also referred to as a flexplate. All BB mopars running an automatic trans will use this plate to attach the converter to the crankshaft.
(3) Neutral balance can be verified with a balance machine....a transmission shop should be able to do this.



Ron

[Challenger_7]

Hi Ron, and glad you are there and thanks for the information;)

I was afraid you would answer my 3rd question with what you said. Out here there is no one with such a facility
What should my course of action be??

As previously mentioned, just to refresh your mind, the current (new) converter came balanced with 2 weights on. The engine is vibrating.
The Mech then took both weights off and the vibration increased a lot, so he returned them back on, and tomorrow he intends to try with some heavier weights.

How should I proceed now?

[firefighter3931]

I would wait for the B&M flexplate and remove (all) the weights from the converter. I would not be experimanting with a heavier weight on the converter.

As for balance verification : do you have an old style "bubble" wheel balancer available ? Possibly, the converter could be placed on the wheel balancer to check for balance. Just an idea....

The description of the B&M plate is referring to the rear main seal which is indeed a 2 piece unit.

What brand of converter is this ?



Ron

[Challenger_7]

Again excuse my ignorance, but what is a "bubble" wheel balancer? Can you provide me with a photo?
In view of the difference in language, no one here will understand what is a "bubble" balancer, and I would need to show them a photo or a specific description, and hope that someone still has this old type.

As for the converter, it is "Trans Star" make.

[firefighter3931]

Again excuse my ignorance, but what is a "bubble" wheel balancer? Can you provide me with a photo?
In view of the difference in language, no one here will understand what is a "bubble" balancer, and I would need to show them a photo or a specific description, and hope that someone still has this old type.

As for the converter, it is "Trans Star" make.

Farouk, years ago wheels used to be balanced on a machine that was very simple....the hub of the wheel was placed on the machine and there was a sight glass with a bubble that told you if the wheel was in balance....similar to using a level in carpentry work. Nowadays, wheel balancers are electronic and computerized.

Here is what a newer style bubble balancer looks like :


http://www.sjdiscounttools.com/atd-8615.html


Member John Kunkel is our resident Tranny Guru....send him a message. Maybe he has an easier way to check for balance.



Ron

[Challenger_7]

Thanks again Ron. From the photo you provided, I now know how it works, and will look for one.
I will also check with John Kunkel, as you suggest.

One question though, you repeatedly said to remove the weights off the converter. These weights are not there to balance it, and removing the weights will not make it imbalanced?

By the way, what is your comment on "Trans Star"? Is it a good make? My mech says it is very good?

Thanks, Farouk

[Challenger_7]

Hello John

As advised by Ron, who has been extremely helpful in guiding me, I am addressing this question to you (pm copy to you).
If you have the time to read through the thread (How to balance an engine) for any possible additions that will be great, otherwise your input on how to balance the converter will be helpful.
We have no machines in Lebanon that can do such a job, and Ron suggested an old bubble wheel balancer, which I will try to locate.
Do you have any other suggestions, or should I not find a bubble balancer, what should I do?
I have ordered the flexplate from B&M in the hope of getting rid of the engine vibration, and awaiting its arrival.

Thanks, Farouk

[firefighter3931]

One question though, you repeatedly said to remove the weights off the converter. These weights are not there to balance it, and removing the weights will not make it imbalanced?

By the way, what is your comment on "Trans Star"? Is it a good make? My mech says it is very good?

Thanks, Farouk

Farouk, the converter should be neutral balance without the weights. The weights are added for engines that are externally balanced with a cast crank....like your 400 and later 440 engines (74-78) Removing the weights will bring it back to neutral balance and the flexplate will take care of the "external" balancing issues. 

Trans star is a descent brand from what i've heard....


Ron

[John_Kunkel]

A couple of observations, the cast crank 400 doesn't always have the humongous harmonic balancer as pictured in firefighters post, most just have an elliptical offset on the inner hub just like the 440 6-pack only thicker; the outer ring is the normal size.

The cast crank 400 needs 100 grams of weight on the face of the converter, this is accomplished by welding two 50 gram weights, one on each side of the drainplug. As mentioned earlier, the B&M #10237 flexplate is a much easier way to go.

Forget the bubble balancer idea, the stator inside the converter is free to float from side to side until actually installed in the transmission, this prevents either spin or bubble balancing without the proper apparatus.

[firefighter3931]

Forget the bubble balancer idea, the stator inside the converter is free to float from side to side until actually installed in the transmission, this prevents either spin or bubble balancing without the proper apparatus.

Thanks for the input John.  The bubble balancer was just some hair brained idea that i thought might work given the limited test equipment available to Farouk. I hadn't even considered the stator being an issue, but now that you mention it...it makes perfect sense. Well i learned some thing new....

Seems we're in agreement on the B&M flexplate and weight removal from the converter to return it to neutral balance. 



Ron

[Challenger_7]

Thank you both for your input, highly appreciated.
As I said, I have orded the B&M Flexplate, and will post my work in progress.

Just for info's sake, in the meantime my mech has continued to add some weights until he felt that the vibration had gone 90%. I asked him why he did not add even more to get rid of it totally, and he said he did, but that took up the vibration to 3000RPM, so he left it where it is.

So, when the flexplate comes, we will have the weights removed off the converter and try it out.

Till then, happy motoring