Internal and external balance.

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Sure, the internal balanced engines are balanced in that manor, inside the engine block while the external balance engine are balanced in that manor as well by way of a off set weighted harmonic balancer and flywheel for manuals or added weights on the torque converter for automatic transmissions.

In general but more so for racing, a internal balanced engine is much more desirable. I have gone plenty quick with an external balanced 360.
 
The factory externally balanced engines to save money. It was usually done with less expensive cast cranks, which use a lighter material than forged steel cranks. The counterweights are lighter so the extra weight to counter the weight of the rods & pistons has to be made up with extra weight, which is hung externally on the ends of the crank to balance everything, as Rumble described.

Race engine are internally balanced because it's suppose to make the rotating assembly more durable and reduce flex a bit. But the extra heavy Mallory Metal slugs pressed into drilled counterweights to do this are expensive.
 
If you're switching to lighter parts(piston, pin, rods) you may be able to move to internal balance without adding heavy metal. Internal balance reduces loads on the front and rear bearings due to crank flex. External balance is typical on engines with insufficient crankcase dimensions for properly sized counterweights, like SBF's or just cost savings in general.

I wouldn't put any money into a cast crank. They do drill nice, but 4340 forged cranks are more available than they've ever been. S/F....Ken M
 
plenty of fast 360s out there with internal and external balanced cranks....

last internally balanced 360 I did...had rods that weight 630 grams..and piston weight 507 grams..crank still took a couple of slug on Mallory on the outer journals..
 
70aarcuda said:
plenty of fast 360s out there with internal and external balanced cranks....

last internally balanced 360 I did...had rods that weight 630 grams..and piston weight 507 grams..crank still took a couple of slug on Mallory on the outer journals..
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That Mallory ,has really gotten expensive,the last few years.... Something to think about.....
 
Also, all 318's are internal balance - right? I understood that only the later 360's were external balance small blocks.
 
sadly.... the 1973 340 uses a balancer... that nobody has in Stock.... also aftermarket balancers are not availible...... as far as I know....
Greetings Juergen
 
So if I am building a stroker 318 to 390 do I need to send out the rotating assy to machine shop and have it balanced?
 
Any time you start swapping parts away from an OEM assembly, you should check and, if necessary, rebalance everything. Even OEM balance jobs can be improved upon.
 
brasil said:
sadly.... the 1973 340 uses a balancer... that nobody has in Stock.... also aftermarket balancers are not availible...... as far as I know....
Greetings Juergen
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Professional Products make a balancer that comes with 3 additional weights that bolt onto the inside of the balancer...one of the weighs is for a cast crank 340....so there is something out there....they come in two flavors...Street version and a SFI version...

ALL 360 are externally balanced.....but the LA and the Magnum are not the same and the balancers cannot be interchanged...the Magnum use less external weight....
 
So when you say it is balanced are you referring to all the pistons weigh the same and all the rods weigh the same? Why would you have to drill the crank and add heavier metal?
 
So I think the counter weights have to counter the weight the rods and pistons EXACTLY....
reddishdsb said:
So when you say it is balanced are you referring to all the pistons weigh the same and all the rods weigh the same? Why would you have to drill the crank and add heavier metal?
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There is a formula that shows how it is figured...
Google how to balance engine
 
All the pistons and rods need to be the same weight, generally some shops allow a + or - of up to 20gms which can add up. The better shops want the rings and piston pins as well. I have done my own, all are the same weight but it takes time which equates to money if paying a professional shop.
There is a formula for engines with the 'V' formation and you will need to tell the shop doing the balance of the crank what is going to be your usual rev range as there is no perfect ratio with this formula. This means you could end up with a vibration at low engine speeds which will drive you crazy in a street engine but not a problem in a high revving or race engine.
If it is external balanced then you will need to provide the harmonic balancer and flywheel (manual) or make sure you have the correct convertor when getting the crank balanced.
Internally balanced engines they can balance the crank without the balancer and flywheel but it pays to take them along anyway, don't forget to take the pressure plate as well with the flywheel (manual).
All 360's are external, all 273, 318 & 340 engines are internally balanced except the '73 340's which has a cast crank.
 
you also need at least one rod bearing set ....the pins and rings need to be included if the machine balances without the pins and rings...ask for your money back..lol

also ask for a copy of the work sheet for future reference...
 
Good one 70aarcuda, I forgot to mention the bearing shells and yes it is ALWAYS good to hang onto any paperwork connected with all parts or outsourced work.
 
One important thing I forgot to mention also is that the connecting rods have to be all the same weight but the big thing here is that 'each end has to be the same weight also' as it affects the balance on V shaped engines.
Unless a person knows what they are doing this should not be done at home on the wife's kitchen scales as they won't be accurate enough anyway, plus you could damage the integrity of the connecting rod as well -- Boom, Grenade an engine quickly.
The guy who does my balancing even allows for the weight of the oil, I have never had a problem or vibration in engines balanced by him. There are a few good engine balance shops out there check around.
 
the weight of the oil? please tell how this guru knows how much oil is on- the crank, rods, pistons etc.
 
Marcohotrod said:
the weight of the oil? please tell how this guru knows how much oil is on- the crank, rods, pistons etc.
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You don't know how much oil is on anything at any given time. For wet sump engines with bores of 4 inches I use 4 grams TOTAL. When you get up to 4.4 bores I add a gram. I also change the percentage of balance as the rod to stroke ratio goes down.
 
^^ There's your answer.
Some things you just have to estimate. That figure will change with rpm, clearances, and oil delivery and controls in any given engine. When the tolerances are measured in .1 of a gram, 4-5 grams is a big value. The factory didn't bother about worrying about stupid stuff like individual component weights.
 
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