383 which harmonic balancer to use?

[roadnotca]

Is it really that big of a deal that it's perfectly balanced?

Now, I'm confused as to why they even offer a blueprinted/internally balanced kit.

The cam runs out at 5600, so the rev limiter will be set at 5300. Don't plan on spinning it that hard for very long, or very often.

Rotating assembly balance is critical all the way from 0 revs to grenaded. Balance this; $$$ for a balance before build, or $$$$ for a boat anchor.
Just my humble opinion.
I've built enough engines to know that with today's options, it's cheaper to buy a crate motor.

 

[blazinzuk]

What they are talking about here is whether the crank needs extra weight on the flywheel and balancer to counter act the weight of the crank. Having your rotating assembly balanced is more of a thing that the pistons and rods are all the same weight.

Unless your crankshaft cost about 400 bucks by itself you will need the balancer and flywheel for the 400 not for the 350

It has to do with the way the counterweights are on the crank. Not whether the rotating assembly is balanced or not

 

[broncoman6524]

ah that makes more sense now.

I'm not to the point of putting it in the truck. So I'll try to call eagle again and see what they say.

All I know is I paid 989 for the crank, rods, pistons, etc.

 

[4X4HIGH]

Let me set you straight. I'm an automotive machinst by trade (21 years). When a 383 stroker is built it MUST be balanced regardless of internally or externally. Now if the engine is balanced internally then you must use a harmonic balancer and flywheel that are "zero balanced" which means no extra external weight. If the engine is balanced externally then you must use a "weighted" harmonic balancer and flywheel from a 400 SBC. This is where you would have tons of trouble if you tried to externally balance a 1 piece rear main seal engine as the 400 SBC flywheel WILL NOT bolt to the 1 piece rear main seal crank.

Do yourself a BIG favor and do not buy a pre balanced "kit". I just recently built a 496 stroker engine for Greg72 that the parts where bought as a balanced "kit" and it's a good thing i checked things out beforehand as it was nowhere near being balanced correctly. You are tons of money ahead of the game if you just buy the required parts and have your local reputable machine shop balance it for you.

If you have anymore engine questions you can PM me and i'll be happy to help answer them correctly for you.

 

[roadnotca]

Let me set you straight. I'm an automotive machinst by trade (21 years). When a 383 stroker is built it MUST be balanced regardless of internally or externally. Now if the engine is balanced internally then you must use a harmonic balancer and flywheel that are "zero balanced" which means no extra external weight. If the engine is balanced externally then you must use a "weighted" harmonic balancer and flywheel from a 400 SBC. This is where you would have tons of trouble if you tried to externally balance a 1 piece rear main seal engine as the 400 SBC flywheel WILL NOT bolt to the 1 piece rear main seal crank.

Do yourself a BIG favor and do not buy a pre balanced "kit". I just recently built a 496 stroker engine for Greg72 that the parts where bought as a balanced "kit" and it's a good thing i checked things out beforehand as it was nowhere near being balanced correctly. You are tons of money ahead of the game if you just buy the required parts and have your local reputable machine shop balance it for you.

If you have anymore engine questions you can PM me and i'll be happy to help answer them correctly for you.

Now we're talking.

 

[4X4HIGH]

Having your rotating assembly balanced is more of a thing that the pistons and rods are all the same weight.

This remark is only half correct. When an engine is balanced you are making sure that all the pistons, rods, rings, and rod bearings all weigh the same but at the same time you are making a correction for the weight of the crank counterweight versus the weight of a piston, ring, rod, and rod bearing. Basically you weigh all the pistons and find the lightest piston then make all the others the same weight, now you do the same for the rods but balancing the rod end for end as well. Now you take a piston, set of rings (for one piston), rod, and rod bearing and weigh them all together. This is the total weight that the crank counterweight needs to weigh to be balanced properly. Now it's time to add or subtract weight from the crank. You now need to make up a "bobweight" (weight equal to piston, rings, rod, rod bearing) and bolt that to the crank (rod journal) and spin the crank and find out where you either need to add or remove weight.

 

[kevin400ex]

there are aftermarket cranks out there now that are manufactured with different counterweights. this is what determines if its an internal or externally balanced crankshaft. most of the eagle and scat stuff are internal balance regardless of the stroke and main size. you can even get a new internally balanced crank for a 400.

for an internally balanced engine you need to know the weight of the (all cylinders should be the same) rods, big and small end, the pistons rings pins and locks and rod bearings. the machinist will take these weights to determine your bobweight and balance the crankshaft acordinly

on an externally blalnced engine, all the above is required as well, but the flexplate/flywheel, and the balancer must be installed on the crankshaft when balancing.