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I am looking at building a 383 with 2 piece rear main 4 bolt block. I need to be internally balanced because im using a clutch setup am I correct on this? If I build a kit from scratch could I just get a internally balanced 383 crank then buy rods and pistons that were all matched in weights or would I still need to get it all balanced?
 

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Balancing ?

To correctly balance an engine they need to have crank,rods,pistons,flywheel or flex plate, dampner,rings and rod bearings when it is balanced.
 

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You can get a flywheel with a balance weight on it that would avoid the extra expense of buying an internally balanced crank. Same flywheel as for a 400 SBC, since the crankshaft is the same as for a 400.

The crankshaft needs to be balanced to the rods and pistons (bearings and pins too), regardless of which ones you buy. Making all the rods and pistons the same is only a small part of the balance job. You are far better to buy these components and have your machinist balance everything. Or buy a balanced assembly (crank, rods, pistons), which is really the same thing.
 

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You can get 383 assemblies as "external" or "internal" balance..

External balance uses a crankshaft with smaller counterweights. Places counterweights in balancer and flex/flywheel. 383 uses 400 chevy components. Detroit engine producers have done this for many years. It is cost efficient and reliable. Perfectly good for street and mild race engines.

Internal balance is just that. All weight equalization is done in the counterweights within the block assembly. Balancer/flywheel are "neutral".

If you buy any assemblies or "kits", internal or external balance. I do not reccommend the "balance job" done by the sellers. A competent balance shop will produce a much closer assembly. Usually + or - 1/2 gram..
 

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I am looking at building a 383 with 2 piece rear main 4 bolt block. I need to be internally balanced because im using a clutch setup am I correct on this? If I build a kit from scratch could I just get a internally balanced 383 crank then buy rods and pistons that were all matched in weights or would I still need to get it all balanced?
If you want a 383 interanally balanced your beat choice would be using a 6 inch rod as the cranks that are used with 6 inch rods have a bigger counter weights and will extrernally balance with out heavy metal.

Don't buy a prebalanced rotator as we have found them not to be very close.
 

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I built a 383 a few yrs back and was externally balanced and never
a problem. Did not get anything balanced professionally, and the guy
I sold it to is still running it....I know where you can pick up a 400
aluminum 168 tooth flywheel pretty cheap if you decided to go
the external route.....My 496 is internally balanced, but the guy
who built it also owns a machine shop, and I guess he thinks
internally balanced is better..That would be a good question to
know.
 

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if you use a later model 87/ later block with the one piece crank seal you can go to a hydraulic roller cam really cheap using stock parts and pick up a lot of performance and reliability :)
 

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I am looking at building a 383 with 2 piece rear main 4 bolt block. I need to be internally balanced because im using a clutch setup am I correct on this? If I build a kit from scratch could I just get a internally balanced 383 crank then buy rods and pistons that were all matched in weights or would I still need to get it all balanced?
I am going thru the same build, 350 to 383. I am using a '69 Truck 350 4 bolt main w/2 pc rear main. The guy at the machine shop said to help keep cost down I can keep my flywheel & balancer if I use an internal balance crank.

Also he wanted to get parts as a 383 kit rather than mix this and that.
 

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Having built a half a dozen 383/388 combos for my cars I can tell you several things.
1) if you want to make over 500 HP or use nitrous, DO NOT use a factory 400 crank- they crack too easy ( I have 4 that will prove this!)
2)Always preassemble the engine before balancing to check for interferance- No 5 rod will hit the cam unless you are using factory 400 rods or some aftermarket rod specifically for this setup. depending on your cam several others may hit too!
3)assemble all rods and pistons and bolt them to the crank (supported in wooden V blocks. then rotate the pistons past the counterweights to check clearance. Eagle cranks with 5.7 rods and the old TRW pistons will clash. gotta grind the counterweights.
 

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383 assembly

I built a 383 that had One of the rod bolts hitting casting flashing near the cam tunnel (just another area to check):anim_25:
 

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I would stick with an internally balanced setup. Buy a crank rods and pistons and have them all balanced professionally at a local machine shop or engine builder. With internal balance you dont have to worry about giving them the flywheel and harmonic damper as they are neutral balance.

And yes, listen to CNC BLOCKS and get a setup with 6" rods if possible. It will make a little more power as there is less side loading on the piston - the rod angle varies less throughout the stroke.
 

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Discussion Starter #12
Ive looked at the scat kits they are around $850 internally balanced im thanking that will be plenty of motor for me. and still keep the cost down pretty good.
 

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383 engines

If you are straped for cash, the external balance parts are cheaper. you can use a 400 balancer and have a regular 350 type flywheel rebalanced when your shop does the balance job. if your engine is going to be race car quality, go the internal route. regards grady
 
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