Internal or External balance 408???

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BrianT

BrianT

Here we go again...
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My block is at the machine shop right now and I have a question about balancing the rotating assembly. I have a forged Scat crank, H beam rods and forged dish pistons.

I spoke to my builder initially and he said that internally balancing was not necessary for my intended usage, which is a Saturday night street bruiser. We were talking about so many things that I kind of blew it off. So I was speaking to him again yesterday and we addressed it again. He said that he can balance it to within two grams on each throw, and for what I'm going to do, it's not worth the added expense of the heavy metal. He said that he would be willing to do it if I insist, but he quoted me $200-300 extra on top of what I'm already paying him to balance it, and I'm fine with that.

Let me say that my builder is a well respected Mopar guy with years of experience building race engines. I would just like to get a few more opinions on whether it is worth it to spend another $300 on internally balancing a street engine. What do you think??
 
My 340 was external, when I had it rebuild I had it made for internal. I prefer internal balance vs external, but that just me.
 
I just found THIS on Summit Racing's website. 12" by .438" diameter slug of Mallory metal for $60. That's not cheap, but won't break the bank??? I have heard of people needing three slugs of MM to bring a crank into balance. Would it really take three foot long slugs???
 
With Respects BrianT,

Info on the block? I.E., pics of the Year designation & 'casting clock'.

---Further, pics of both 'decks' after teardown ---

If possible :D
 
mech1nxh said:
With Respects "T",

Info on the block? I.E., pics of the Year designation & 'casting clock'.

---Further, pics of both 'decks' after teardown ---

If possible :D
Click to expand...

It's a 1990 roller block LA. No pics of the "casting clock". Why would you need pictures of the "decks" of my block when we are talking about balancing?? Here ya go, I hope it helps?!?

IMG_20120805_073358.jpg
 
BrianT,

My opinion, for what it's worth (not much probably), would be to pay to have it internally balanced. What's your total build cost, $6,000? That means $300 is equal to about 4% of your total cost. The internal balance gives you the freedom of not worrying about a specific harmonic dampener or flywheel/flexplate to keep the engine in balance. I had my 408 internally balanced and it cost me $225.

Here's a good overview of the process:
http://www.eaglerod.com/index.php?option=com_content&task=view&id=27&Itemid=25
 
I would prefer internally balanced. Having a rotating assembly balanced at the source rather than further out just makes more sense. My 408 is internally balanced.
 
Balance it so anything you attach such as damper, flywheel, or converter can be installed neutral balanced. Easier to install in any car in the future. Never go cheap on the long block. If the weight is off just a little for the externally balanced parts the motor will be junk. Make it so all parts get Neutral balanced for the motor.
 
This is why I love the Scat kits...they come internally balanced. Scat charges 200.00.
 
ou812 said:
This is why I love the Scat kits...they come internally balanced. Scat charges 200.00.
Click to expand...


I'm not sure what you mean Brian? This IS a "Scat kit" came directly from them all in one box. EVERYONE recommended buying it unbalanced and letting my builder do it himself?
 
ou812 said:
This is why I love the Scat kits...they come internally balanced. Scat charges 200.00.
Click to expand...

I went with a internally balanced kit from scat. My builder recommended it. Said they could balance it for much less than he could with the price of Mallory. All they deal with is scat unless a customer brings in his own stuff of course. He says he does double check them and has never had the need to add to the balance from scat. My guys more say a chevy guy but they have been in the biz for 30+ years and has done his far share of mopars.
 
Internally balance it. And I don;t trust any manufacturer telling me everything's ducky because everyone's idea of "ducky" is different. I don;t want "good enough". I want a balance card and to know the guy doing it.
 
I'll add my two cents here.... Internal balance. The only way to rock!
 
I wouldnt trust any company who sells a kit already balanced, I don't give a fck who it is including Scat. It is gunna be checked no matter what, been there done that and NEVER again.

On another note I had my last crank 'Scat 4" Forged' balanced and it took 2 sticks of Mallory. Understand now this is an $800.00 Crank. Why in the HELL cant they get it balanced for that $800.00 when they are making it. That just blows me away.

Oh and YES Internal Balance!!
 
all 340's were internally ballanced . if youre using a ballanced rotating assembly, it is by definition "internally ballanced"
 
a68postcar said:
all 340's were internally ballanced . if youre using a ballanced rotating assembly, it is by definition "internally ballanced"
Click to expand...

Survey SAYS..... X :D

Nope, cast crank 340's were external balance
 
Hey Brian,

Definately go with the internal balance. You can get the Scat kits balanced or unbalanced. Also, my 408 has Scat Forged Crank, with Scat H beam and Icon slugs. Hughes Engines (I live only an hour away from their shop) had the pieces and balanced everything, but did not have to use the Mallory. Just a little puzzling that you would need to go with the heavy stuff.......but maybe I am missing something?? Possibly piston weight. Mine are 16cc dishes, but I run a Magnum Edelbrock head on a 91 LA.
 
aengineguy said:
Hey Brian,
...my 408 has Scat Forged Crank, with Scat H beam and Icon slugs. Hughes Engines (I live only an hour away from their shop) had the pieces and balanced everything, but did not have to use the Mallory. Just a little puzzling that you would need to go with the heavy stuff.......but maybe I am missing something??
Click to expand...

Our rotating assemblies are the same. Mine has not even gotten to the stage of balancing yet, I was just discussing it with my builder. It might not need an ounce of weight and that is what we are hoping for. But I am prepared to buy the Mallory metal if necessary.
 
Forged crank,H beam rods,forged pistons and external balance ? You went with the best so far,dont comprimise now. I had my 408 assm internal balanced for under $300. I have forged Mahle pistons and needed no mallory. What brand pistons do you have and are the heavy ?
 
Demon 408 said:
What's your total build cost, $6,000?
Click to expand...

Ha! I have that much in PARTS for the long block. No headers, torque converter, carb or machining costs...

Mo-Par said:
What brand pistons do you have and are the heavy ?
Click to expand...

They are Icon 745 pistons. They weigh 635 grams with the pins. I don't know how this compares to other forged stroker pistons.
 
BrianT said:
I'm not sure what you mean Brian? This IS a "Scat kit" came directly from them all in one box. EVERYONE recommended buying it unbalanced and letting my builder do it himself?
Click to expand...

Not everyone! Because I would not have recommended that.
 
Not trying to start an argument Brian because I respect your opinion, but tell me why? ALMOST everyone said that I shouldn't trust the mass production line and let my local builder do it and get it right. I'm just curious why you, as a machinist, would want to have to possibly correct someone else's work instead of just doing it right in the first place??? Plus, it's less money for you as a business owner.
 
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