xxsaint69x

Here is the problem. My new engine is supposobly internally balanced. I took the weight of my street twin flywheel and had it double checked for 0 balance(dont really trust the shop that checked it for 0 balance) but i also called mcleaod and they verified that once i take the weight of the aluminum flywheel it will be 0 blanced within 1 gram.

Well needless to say anything over 1500rpms feels like the end of the world.
When i put the weight back on the flywheel it is smooth. So here is the question....Is the motor really internally blanced? Or maybe my flywheel is totaly out of wack if i take the weight off even thought the shop and mcleoad claims that the flywheel is 0 blanced without the weight on it What do you guys think?
Marcin

number77

maybe you TQed the flywheel on incorrectly, and did it correctly the second time?

xxsaint69x

never took the flywheel off U can take the weight on/off without touching anything.
Marcin

MachinistOne

Late-model 1 Piece rear main seal cranks are internal balanced on the front and external on the rear, you need that weight to be balanced.

cliff929

It all depends on what he had done. And the crank he bought. I have a Lt1 383 that is internally balanced And I had to get a flex plate from ATI as they I believe are the only ones who make them O balance. Not sure. But it does sound like if you put the weight back on and it goes away. It is not totally internal balanced.

Anyways good luck hope the best for you.

SStrokerAce

You can balance them internally without the weight, it's actually better for the whole assembly to do it that way, just harder to do.

Sounds like you have it balanced with the weight on the flywheel.... but the question is... why did you let them do it if you don't trust them?

Bret

xxsaint69x

i just had the shop check the flywheel to make sure it was 0 blanced. I purchased the motor already assembled and have been told i will need a neutral balanced flywheel since the motor is internally balanced.

I am not even sure the shop checked it, but either way mcleaod confirmed that the flywheel will be neutral balanced once the weight is taken off.
Marcin

btw it is a cola crank

rskrause

If you were charged to internally balance your rotating assy., you deserve a refund.

Rich

Dryseals

Did the engine come with the fly wheel? Most shops want the flywheel to do the balance even if its external. You can always check the number on the crank and see the intented use of the crank.

1racerdude

If it works with the weight on then leave it (weld on) on and go have some fun.

rskrause

One of the big advantages of internal balance is that you can bolt up any neutral balance flywheel/flexplate with no problem. Provided, of course, that the internal balancing was done correctly and that the flywheel IS neutral.

Rich

Dryseals

Thats a new one for me. I just had a one peice seal 95 model crank come back from the shop I have dealt with for years, they never mentioned that. I did have to go with another set of rods as the big ends on the Eagles I had were a tad heavy. The newer cranks are a bit lighter do to the powdered rods. They had the flywheel which is a neutral balance unit. They did not use the damper I had as it is a fluid type.

rskrause

There is some confusion in terminology here. All cranks have counterweights. So, in that sense they are all, at least partially, internally balanced. However, with a Chevy 350, the counterweights are not heavy enough to completey balance a stock piston and rod assy. so weight is added externally. It could be added internally, in the form of mallory (heavy) metal. But this is expensive. it's cheaper and add the weight externally. On the stock motor, the weight is added at the rear. It could be added at the front instead, or both. But it's easiest to do at the rear. Stock rotating assys are not individually balanced. The production tolerances are tight enough that the same amount of weight is added externally without any checking. It works quite well, so they must be doing something right. How close it actually is to perfect, I have never measured.

When an aftermarket RA is used, there are two basic choices WRT balancing. The RA can be balanced against the standard external counterweight and a stock balance flywheel/flexplate used. The RA can be fully balanced internally using mallory and a neutral blance flywheel used. The latter choice is suppposedly better interms of reducing crankshaft internal torsional stress, though there are planty of externally balanced motors that seem to live fine. The big advantage seems to me to be the ease of using a neutral blance flywheel/flexplate.

Rich

MachinistOne

Early SBC's are "internally balanced" as you said, meaning that all the balancing is done on the crank, the late stuff has a weight on the flywheel, BBC's are externally balanced, small block fords have a 28oz, or 50 oz external balance, etc

There are many motors than are external balanced, and while it may be true about the torsional stresses...in a street motor the main advantage of having a truely internal balance motor is being able to replace the damper, flywheel, flexplate etc with another "0" balance unit, and KNOW that the motor will still be in balance, that the original balance job will still be good when you start replacing external parts.

Factory motors are called "over balanced" which means that there is more weight on the counter-weights than in the rods/pistons, an over-balanced motor will not cause vibration unlike a "under-balanced" motor that will shake your fillings out. This is why like you said, they can assemble motors without balancing parts, they have a over-balance.

Every motor that I have seen internal or external if balanced correctly will be a smooth no-matter of where the weight is placed.

So in answer to your question, they most likely balanced your motor assuming that the weight would be there, a terminology error, they really should have added mallory and truely internally balanced the motor like you specified, but you should have no ill effects from running the weight.

xxsaint69x

so as long as it feels smooth i should be fine?
Wont screw up the bearings?
Marcin