383 Internally or Externally Balanced???

[brickyard69]

I searched for this answer in past posts , but could not find the answer.

I am doing my homework in preparation to building a 383 for my 69 Camaro. I will be running a Muncie 4speed.

I see all the lower priced rotating assemblies are externally balanced and use a flexplate for an auto trans.

If you are running a manual trans do you have to use an internally balaced kit?

Goal for the motor is 430hp.

I was thinking about buying a crate motor but I want the ppride of having built my own motor.

Thank you for the input.

[brickyard69]

While I am thinking about it. What is best the 6" rods or 5.7?

What is the difference?

[harshman]

Internally balanced assembly. The flywheel comes balanced. Why? I have no idea but that is what I learned from my car (T56).

[morrisclassic]

Kits usually come balanced for an automatic. You can buy a light weight flywheel that is counterbalanced for a 400 which is what a 383 is essentially. Or an engine shop that balances engines can help you if you
want to use a standard flywheel. The 383 can be balanced internally but is expensive because the mallory metal that they use is expensive. I may have spelled the word "mallory" wrong.

[morrisclassic]

Use the 400 balancer. The 400 and 454 were external balanced
engines. Use the 5.7 or 6 inch rods. Scoggins and Dickey in
Texas has the best deal on stroker kits.
Billy

[Norwoodx55]

You don't NEED to run an internally balanced assembly with a manual trans., but you will need to use a flywheel intended for an ext. balance engine(counterweighted) An inernally balanced assembly is generally the prefered way to go, albeit more expensive. The cost can be offset if you already have a flywheel and damper for an internal motor(any small block BUT a 400) As for the 5.7 vs. 6" rod, I think most builders prefer the 6" for the improved rod/stroke ratio. Another thing to consider if using a 6" rod is that it weighs more than the 5.7. So if you do use a less expensive externally balanced crank you can run into the expense of adding mallory metal (as mentioned in another post) just to get the assembly balanced. Many of the int. bal. cranks are offered with the option of a 5.7 or 6" rod application, making balancing easier/cheaper to do. Hope this helps.
Brett

[brickyard69]

NorwoodX55,

if I understand you correctly, I CAN use an externally ballanced kit with a 400 flywheel. Same balancer as the auto?

Has anyone built an externally balanced 383 with a manual trans?

Where is a good plave to the correct flywheel?

Thanks everyone!

[morrisclassic]

Yes My 383 is external balanced with a 15# z/28 flywheel that has been machined . You will need the 400 balancer and a counterweighted flywheel.
Cheaper to buy the 400 lightweight flywheel. It cost 95.00 to have my flywheel machined.

[morrisclassic]

Forgot to answer the question about the balancer, manual or automatic
doesn"t have anything to do with the balancer, it"s just a 400 balancer.
The flywheel has to be counterweighted.

[brickyard69]

If I buy the externally kit already balanced, how do I balance the flywheel? Doesn't it have to be matched to the kit?

[morrisclassic]

I"m not sure if you can just switch from an automatic flywheel to a standard. Call SDPC AT 800-456-0211. They can balance the assembly with your choice of flywheels. Then you will be ready to assemble the motor upon parts arrival. They are good to deal with.They have several stroker kits from 899.00 up. Good quality parts.

[Lowend]

Yes - you can make an external balance work with a M/T... AND the internal balanced system is better.
lighter weight, truer balance, fewer harmonics, and if you ever need to replace the flywheel you don't have to rebalance the rotating assy to make it true.
Not to mention that the internal balance flywheels are cheaper

[SStrokerAce]

The internal balance will also put less stress on the crankshaft, which is always a good idea for the longevity of the setup. Not to mention that the internally balanced flywheel is going to have a lower inertia as well.

Bret

[MrQuick]

yeah if you gonna have it apart or build it from scratch might as well have it set up internally, I don't even mess around with counter balance flywheels and balancers. Plus the reasons above.

[brickyard69]

Anyone else running a 383 with a manual trans?

[Lowend]

Yep - me!

[ertoys]

This is a great thread because I called a machinist in St Louis today and I about crapped my pants when he told me $750.00-$850.00 for machine work.

That is for Boring, magnaflux, cleaning, stroker clearancing the block, installing the cam bearings and balancing the entire assembly internally.

Does this price seem expensive? or average? low?

[SStrokerAce]

No that's about in line.

For me to get a OEM block up to race blueprint takes $1700+ in block work alone not to mention the balancing.

Bret

[CarlC]

There are usually more off-the-shelf pistons available for a 5.7" vs a 6.0" rod.

[6'9"Witha69]

Not a manual here, but to reinforce what has been said, I definitely say Internal! I have had a starter eat an external flywheel. If you can't find your balance card, get ready to tear out the rotating assembly.

And yes, 6" rods make for a heavier balance assembly! I had to have 3 slugs put in my Scat crank to true it up! Usually in a 5.7 application it is under 2. Most machine shops charge per slug and mallory metal is 'spensive! And 5.7 rods let you use the more common (read:readily available, better selection) pistons since 6" rods need a piston with a raised pin height and shorter skirts.

[Lowend]

Man for out here in San Jose that is cheap for machine work...
I expected my 383 w/6" rods to need some mallory metal, but it balanced out without Mallory. Maybe I'm lucky, or maybe my machinest is just more detail oriented than most.

[Davezz28]

Most of the aftermarket "383" cranks will internal ballance if you keep the bob weight under around 1850g. If you use a reasonable weight 6" rod (600-650g) and a forged piston (around 525-545g w/pin) you should be able to internal ballance the crank. You should check with the crank MFG before you purchase and check what the bob weight their cranks will ballance to.

You will "usually" get a lighter bob weight with a 6" rod due to the fact that a piston for a 6" rod 383 is lighter than a piston for a 5.7" rod motor. The recprocating and rotational weight of the 6" rod is a little more than the 5.7" rod but the lighter piston usually is more than enough to offset the additional rod weight.

Another reason to look at using 6" rod is some of the "383" cranks out there have counter weights too large for the 5.7" rod and the piston will hit the counter weight.

Internal ballance is better on bearing durability and like was stated before, if you have the crank internally ballanced, you can change flywheels etc. with out reballancing.

If you are building a motor from scratch, you should work with you engine builder and decide what you want to do and purchase the correct parts so you don't run into problems

Dave

[6'9"Witha69]

If you are building a motor from scratch, you should work with you engine builder and decide what you want to do and purchase the correct parts so you don't run into problems
SOLID advice!

[Zee]

Like David said. My experience with 383s is that you should determine what rod length you want to use then get the crank. The better cranks will specify what rod length they are made to work with. The cranks made for 6.0 rods have larger counterweights because of more clearance between the counterweights and the piston skirts at BDC. Secondary advantage here is that less or no Mallory will be required for an internal balance. Cranks made for 5.7 rods have smaller counterweights as there is less clearance for them. Problem here is to internally balance, you will likely need more Mallory.

Generic 383 cranks are typically for the 5.7 rod as it will clear either rod and avoid having to produce two cranks for essentially the same application. This saves production and inventory costs for the manufacture but shifts balancing costs on to the end user if they want to internally balance regardless of rod choice. To minimize the cost shift, most want you to externally balance.

IMHO, there are plenty of pistons available for the 6.0 rod and I would get a crank specifically made for 6.0 rod use and a light weight piston which may eliminate the need for Mallory to internally balance. There are also a few 5.85 rod kits out there which may be the best of both worlds.