Oh crap..... Internally balanced engine with an external balance flex plate?!

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SRT_DSTRHOLC

SRT_DSTRHOLC

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So when I originally purchased my flex plate it was from a friend of a friend, said it was internal balance flex plate. Gave it to the machine shop along with the bottom end and internal balance balancer. They got it done and never looked back. The engine was just taken out because I am replacing a transmission seal. I also bent the flex plate where the bolts go, and was looking to replaced it.... Then I noticed that the one I have from B&M has the notch cut out of it which is the external balance one!!! Damn it!!.... I need help on what I need to do... Can I replace it with the internal balance one or what?!?


For those of you about to ask about vibrations, the car vibrated a lot already because it's a stroker making 500hp and pound exhaust 3inch with turn downs under the car.
 
I would contact the machine shop, more than likely they balanced the rotating assy with the the balancer and flex plate as one unit. If that's the case I would just purchase the same part number flex plate and use it. If they didn't balance as a unit I would use the internal balance flex plate. But the shop is the key in my opinion. But there are others here with a lot more knowledge than me.
 
Yup. Sounds like it was internally balanced with an externally balanced flex plate. No big deal, really, just get another one just like it.

Did the engine run good and smooth with no vibration?
 
Way back I had a 360 (OE external-both ends) & after new pistons etc I had it internally balanced with the OE external balance dampener up front and a neutral torque converter/neutral flexplate on the back. If I think of it I'll ask him if using a neutral dampener will let the bobweight come in lighter
 
Sweet, honestly like I said the car vibrated a lot because of the engine size, no interior so it was hard to tell. I'll just get the same one, bolt it in and see if I notice anything this time around
 
If you don't run down the machine shop and ask them then you may be missing the boat.... engine size by itself does not cause vibrations.
 
When you balance a crank, if you use a neutral weighted harmonic balancer and a neutral weighted flex plate/fly wheel, you don't spin them, it just adds more weight to mess with. It's only if the assembly is externally balanced do you spin the entire mess.

I would simply call the shop and ask how they balanced it and then use the suitable flexplate, which will probably be returning the external flex and getting a neutral flex. S/F.....Ken M
 
EchoSixMike said:
When you balance a crank, if you use a neutral weighted harmonic balancer and a neutral weighted flex plate/fly wheel, you don't spin them, it just adds more weight to mess with. It's only if the assembly is externally balanced do you spin the entire mess.

I would simply call the shop and ask how they balanced it and then use the suitable flexplate, which will probably be returning the external flex and getting a neutral flex. S/F.....Ken M
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I asked for them to internally balance the bottom end. I gave them the balancer which is neutral/internal balanced and the flex plate that apparently is external balanced. This was done awhile ago, but the engine was just recently assembled last year
 
nm9stheham said:
If you don't run down the machine shop and ask them then you may be missing the boat.... engine size by itself does not cause vibrations.
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So you are saying a big engine won't vibrate a car that it would be like the honda my neighbor has on start up? I don't agree with this. Even stock 440 cars would shake at idle and vibrate the car.
 
Fst73_410 said:
So you are saying a big engine won't vibrate a car that it would be like the honda my neighbor has on start up? I don't agree with this. Even stock 440 cars would shake at idle and vibrate the car.
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Well....yeah. The one stock 440 I rebuilt was smooth as silk at idle, and smoother than most 4 cylinders....whatever.

The problem here is that we cannot possibly tell the vibration that you are feeling; the info is too limited to really say what it is: motor or trans mount? Driveline? Exhaust bumping around? Big motor? The advice to check with the machine shop is sound advice. They could have balanced it WITH the external balance flexplate or could have set it aside and internally balanced it; you just don't know at this point. The PO could have been told and not understood....

But do as you like..... you are spending $$ on a 50/50 shot of fixing the issue at this point, and asking the machine shop may help improve those odds. (BTW, this same discussion took place about 2 months ago here!)

Just one question: Does this flexplate have a 'bite' of material missing out of one edge? Or a weight on one side?
 
Fst73_410 said:
Sweet, honestly like I said the car vibrated a lot because of the engine size, no interior so it was hard to tell. I'll just get the same one, bolt it in and see if I notice anything this time around
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To say an engine vibrates a lot because of its size is your mind trying to cover up a problem.
 
Fst73_410 said:
So you are saying a big engine won't vibrate a car that it would be like the honda my neighbor has on start up? I don't agree with this. Even stock 440 cars would shake at idle and vibrate the car.
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Yeah we are. My 500ci Viper Truck idles just like our 06 Charger. Now my 96ci Harley vibrates constantly. The size (externally or internally) of the motor has NOTHING to do with the vibrations.
 
So they neutral balanced your flex plate.

Like nm9 says, it doesn't matter the displacement or power, if balanced correctly it should rev up and down smoothly.
 
The less number of crank throws the more it will vibrate and require a higher RPM to stay running. Most 4 bangers use a balance shaft so the accountant types don't get all worked up sitting at idle with the AC on.
 
Rapid Robert said:
Way back I had a 360 (OE external-both ends) & after new pistons etc I had it internally balanced with the OE external balance dampener up front and a neutral torque converter/neutral flexplate on the back. If I think of it I'll ask him if using a neutral dampener will let the bobweight come in lighter
Click to expand...
Well, you did not have it internally balanced if it was an external balance damper up front; the weight changes were necessarily inside but the front half of the engine would still be considered external balance. (The whole term of 'external balance' is a bit misleading anyway; it is just a setup where part of the counterweight is external.)

And the bobweight has nothing to do with the counterweight locations, internal or external; bobweight is all in the pistons/rods/pins/etc. If you want to see, go to the Eagle site in the technical section and look at the bobweight computation example they show. Maybe what you are thinking is if the neutral balanced damper could allow no material added to the crank? The answer is that you would need MORE weight on the crank counterweights.

The way to have less material on the crank counterweights is to lighten up your rods/pistons/pins enough; that change lowers the bobweight against which the counterweights are balanced. We did this with our 340 and a 273 cast crank: part of our piston and rod selection was to get our piston/rod/pin weight to be much lighter than the 273/318 stock weights, and so only removing crank material was needed. As I recall, 80+ grams was taken off of each end of the crank, mostly in the outermost counterweights, but also a bit on the second outermost ones.

What is bothering me about having so-called external balance on one end and neutral balance on the other end is that the counterweight addition/removal on the one end will be different on the other end by a significant amount. This will end up with different counterweight moments on one end versus the other and some degree of end-to-end rocking vibration. So you could well end up with some level of an unusual vibration that you normally would not have.
 
Thanks for your description. I talked to Brian at IMM already. Like I stated, which he also stated. If the engine was balanced with the current balancer and flex plate, they more than likely added more metal to the crank. Meaning just replace the balancer. When the engine goes back in if I notice anything, I'll pull it again.
 
I already told you that it was an external flex plate so it has the chunk out and a internal balancer up front. Like I also said, the engine was balanced in 2010, and recently assembled last year. I doubt they would remember.
nm9stheham said:
Well....yeah. The one stock 440 I rebuilt was smooth as silk at idle, and smoother than most 4 cylinders....whatever.

The problem here is that we cannot possibly tell the vibration that you are feeling; the info is too limited to really say what it is: motor or trans mount? Driveline? Exhaust bumping around? Big motor? The advice to check with the machine shop is sound advice. They could have balanced it WITH the external balance flexplate or could have set it aside and internally balanced it; you just don't know at this point. The PO could have been told and not understood....

But do as you like..... you are spending $$ on a 50/50 shot of fixing the issue at this point, and asking the machine shop may help improve those odds. (BTW, this same discussion took place about 2 months ago here!)

Just one question: Does this flexplate have a 'bite' of material missing out of one edge? Or a weight on one side?
Click to expand...
 
I doubt it, my car idles at 1400 rpm with the big camshaft I have, also on e85 and 4200 stall. So if your car still idles at 900rpm or less then we are talking about different situations. And the excuse of Engine size wouldn't dictate if the car vibrated is vague, so you're saying a pro mod or anything should run smooth too?


nm9stheham said:
Well....yeah. The one stock 440 I rebuilt was smooth as silk at idle, and smoother than most 4 cylinders....whatever.

The problem here is that we cannot possibly tell the vibration that you are feeling; the info is too limited to really say what it is: motor or trans mount? Driveline? Exhaust bumping around? Big motor? The advice to check with the machine shop is sound advice. They could have balanced it WITH the external balance flexplate or could have set it aside and internally balanced it; you just don't know at this point. The PO could have been told and not understood....

But do as you like..... you are spending $$ on a 50/50 shot of fixing the issue at this point, and asking the machine shop may help improve those odds. (BTW, this same discussion took place about 2 months ago here!)

Just one question: Does this flexplate have a 'bite' of material missing out of one edge? Or a weight on one side?
Click to expand...
 
charger426 said:
Yeah we are. My 500ci Viper Truck idles just like our 06 Charger. Now my 96ci Harley vibrates constantly. The size (externally or internally) of the motor has NOTHING to do with the vibrations.
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Your srt 10 truck is fuel injected and made to run at a lower rpm. Do a 512 stroked 440 with 2inch headers and 3inch exhaust and tell me it doesn't feel like your Harley, oh yeah plus the car has poly engine mounts and transmission mount with a torque strap and weighs 2800 pounds, no interior, roll cage and frame connectors. If you're telling me it's suppose to run like a new car. Thanks for your help.
 
Let me do one post before everyone misunderstands what I am saying. The car is full of poly bushings, poly spool mounts, poly trans mount and torque strap.410 stroker, idle at 1400, turn down 3 inch exhaust. No interior at all besides seats and dash, everything fiberglass except doors. Put your had on the side of of the car and you feel the vibrations of the engine though the poly mounts. I've had this car up to 6k and 120-140mph. On start up has 80psi oil pressure. Engine has 735 miles on it. Was told if what I had was an issue that there would be a noticeable vibration unlike anything else, I have not noticed this that I recall. https://instagram.com/p/9R4l1JR0-F/ Open headers

https://instagram.com/p/627GMjR05Q/ Cold start
 
My 610 horse 408, that runs 10.60's. With a solid roller 760 lift cam, idles at 950 rpm, and purrs like a kitten without rattling the car apart....just because its not an efi engine doesnt mean it rattles the car apart. I also have poly spool mounts.

For comparison sake, I had a less than optimally built 323 that idled high, and shook more than the 408.

The "big engine" shakes analogy is a mask for other factors. Just like "big cams have to idle at 1400"...
 
johnnymac2k6 said:
My 610 horse 408, that runs 10.60's. With a solid roller 760 lift cam, idles at 950 rpm, and purrs like a kitten without rattling the car apart....just because its not an efi engine doesnt mean it rattles the car apart. I also have poly spool mounts.

For comparison sake, I had a less than optimally built 323 that idled at 1100, and shook more than the 408.

The "big engine" shakes analogy is a mask for other factors.
Click to expand...

Thank you. I still think my saying the car shaking is being taken out of context. I could say the car isn't shaking and you guys would be on my side. Maybe I over exaggerated the shaking. My car still idles at 1400 which E85 needs and my big cam with gas was at 1100 before e85. The car doesn't shake crazy or anything. I was just saying I feel the car, the exhaust kisses the floor boards too. If you put your hand on the hood of a high powered car, I'm pretty sure you would feel it .
 
Gotcha. I think its just the loose use of terms like "big cam" "high horse power" engine. And such. Not that you are using them improperly, they are just taken differently by others. A 1500 horse turbo car can idle smoother than a 300 horse sb. Anyways besides the point, and it appears you got some guidance on your original question. I know of several production engines that were internal balance, but have external balance flexplates. As the boys mention above if it was balanced like that, probably not an issue. Good luck!
 
johnnymac2k6 said:
Gotcha. I think its just the loose use of terms like "big cam" "high horse power" engine. And such. Not that you are using them improperly, they are just taken differently by others. A 1500 horse turbo car can idle smoother than a 300 horse sb. Anyways besides the point, and it appears you got some guidance on your original question. I know of several production engines that were internal balance, but have external balance flexplates. As the boys mention above if it was balanced like that, probably not an issue. Good luck!
Click to expand...

Thank you good sir
 
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