i just built a 383 stroker with a one piece rear main seal. what do i have to do to externally balance the motor???

 

take it to a engine shop

 

Take to machine shop that does engine balancing:

Pistons/pins/locks if floating pistons
rings
rod bearings
rods w/caps, nuts, rod bolts
externally balanced crank
externally balanced flywheel/flexplate
externally balanced balancer

If crankshaft is an internally balanced design then the balancer and flexplate/flywheel don't need to be taken since they will be neutrally balanced.

They'll need all that to balance the rotating assembly. You can't balance an assembled engine.

 

I think you just made someone very, very mad

 

na i think thats bullsh*t. i talked a few machine shops and they said to use the 400 balancer and that i had to add an additional weight to the flywheel. they called it a "bob" weight or somthing. has anyone ever heard of somthing like that?

 

i go to alfred state collage and my instructor said that the balancing issue can be corrected without dissasembling the engine.

 

Wow it was like just yersterday on how bad this is. While your talking about this I had my engine balanced the correct way Im assuming since nothing was touched on the flexplate or balancer. Will I be ok switching balancers because i would like to upgrade to a SFI balancer?

 

Something like the everyday 305/350 could be easily balanced because the balancer and flexplate just need to have a neutral balance.

383/400 have the balancer/flexplate weighted to correct the rotating assemblys off-balance.

If you want it done right tear it apart.

Shaggy what engine are you running?

If its an internal balance and it was done right youll have no problem swapping out balancers.

 

It sounds to me like the rotating assembly was just thrown together with no balancing at all, internal or external. I wouldn't count on it living long.

 

I was thinking the same thing.

Get him to guarentee your engine when you start pounding bearings out of it.

If you're building a 383 with a one piece rear seal then it's not a factory 400 crank. Is the aftermarket crank internally or externally balanced? If it's internally balanced then you can't put an external balancer, flexplate/flywheel onto it. If it's an externally balanced crank then yes it needs a 400 balancer, flexplate/flywheel but just installing those doesn't balance the rotating assembly. Unless you buy a new replacement 400 balancer, it will be at least 25 years old. I'd throw any old balancer away. They just have offset weights to counteract the missing internal weight on the crankshaft.

Whenever internal parts have been changed, especially different pistons from what the crank was designed for, the entire rotating assembly needs to be rebalanced.

When I took my 540 parts in for balancing, it was put on the spin machine 8 times before all weights came out to zero weight.

 

i bought the whole bottom end as a kit. it was supposed to be "assemble and go". im not stupid i know what im doin, i wouldnt just "throw" together an engine. but the manufacture's that i got the kit from oviously dont know what the hell they are doin because ive been tryin to figure out this problem for 4 weeks and the company's just cant seem to get they're stories straight about what they sold me.

 

Do you have a link to the kit you used online or anything?

 

my instructor isnt guarenteeing anything. he told me it will throw bearings within 100 miles thats how bad its unbalanced. im not stupid enough to drive it like that. the block is bored 40 over instead 30 does thast make a difference? i do have links to where i bought the kit from but they keep bull****ting me about what i need to do

 

isnt the weight on a 400 the same oz. as a 350? i know for a fact that its in the same location

 

Post a link and maybe we can help figure it out.

 

The weight of what?

 

exactly what is the problem?

What parts came in your kit, and what parts did you reuse from your existing engine?

 

the weight on the flywheel

 

How would I be able to tell how it was balanced? It looked like he grinded on the rods. He said he matched pistons best he could to each rod. I could see he did some considerable grinding on the crankshaft. The flexplate and balancer looked untouched.

 

Is the "stock" flywheel on the engine, or a "special" one for a 383 stroker that has the proper imbalance like on a 400?

 

i didnt reuse anything. new cast scat crank, speedpro pistons, forged rods, speedpro cam etc. every thing is brand new. the problem they told me that its a balanced assembly and ITS NOT. now they keep bull****ing me about that im wrong and ive had plenty of "qualified" people look at it and they tell me its not balanced properly and they dont even know what to do

 

if the balancer and flywheel are untouched than than its an internally balanced motor

 

The original small block chevy engines with the 2 piece rear main seal were all internally balanced, there were no counterweights outside the block. The balancer and flywheel were neutrally balanced. When they did the 400 block, Chevrolet decided there wasn't enough room inside the engine to put all the counterweight on the crankshaft, so they added counterweights to the dampener and flywheel. This added weight outside the block makes the 400 an externally balanced engine.

When the 383 first started becoming popular, everyone was using modified stock 400 cranks, with the appropriate dampeners and flywheels, so most but not all 383s were externally balanced as well.

When Chevrolet went to the 1 piece rear main seal, they changed the shape of the mounting flange on the rear of the crankshaft. To offset this change, a small weight was added to the flywheel. These engines are still usually called internally balanced though, and they still use the same neutrally balanced dampeners.

Aftermarket 1 piece RMS stroker cranks can be confusing though, since they can be internally or externally balanced. Since there were never any factory 1 piece RMS 400 crankshafts, they don't have any sort of a reputation to live up to, so to speak.

 

yea the original flywheel is on the engine. its a one piece rear main seal engine. a 400 flywheel wont bolt up

 

If it shakes like a dog sh!tting tacks, it's an imbalance problem. I would think this is still externally balanced, and you're using the wrong flexplate (I'm assuming auto trans) and or balancer. Did your rotating assembly come with a balancer and a flexplate?

 

As long as when your engine was balanced they didn't change the factory balance of the dampener, you can just swap it over.

 

I dont think its internally balanced since I used a stock 400 flexplate and balancer. Although he didnt touch them I assumed this was still considered externally balanced but this stuff gets confusing. I just paid the guy but am pretty clueless on what he actually did. I noticed some balancers have some drilled spots on them while some dont. Whats the difference?

 

That's half the problem right there. You need one with the 400 imbalance, not the imbalance for a 350.

edit-ask me how I know, been there done that.

 

Aftermarket 1 piece RMS stroker cranks can be confusing though, since they can be internally or externally balanced. thats true and the company that i bought the kit from cant tell me anything about the kit they sold me. and stupid me i dont remember if the crank was drilled or not when i assembled it

 

Which balancer is on it? One for a 350 or 400?

 

no the kit didnt come with a balancer/ flexplate

 

Have you got that link?

 

lo-tec, the motor that u bilt have a one piece rear main? if so what exactly did u do to balance it?

 

ape-iron, na i dont have the link it. the kit came from northeast machine shop out of tonawanda

 

My buddy and I swapped an LT1 into an 84 Z. When he order the flywheel, he ordered one "neutral" balanced, and that's what he got. Since it's a one piece RMS, it has some imbalance built into it from the factory. Well, the jackass at summit sent us one that was really neutralled balanced, and it ran like the dog sh!tting tacks. Different imbalance, same principle. Here is the part # from summit:

SES-3-60-11-026

WRONG APPLICATION, but the right principle. You need a flywheel with the 400 imbalance for a one piece RMS. Also, again, what balancer is on the motor?

Edit*****merry x-mas

HAY-10-024 looks like what you need for the flexplate. From summit:

Flexplate, SFI, SBC 383 Stroker 1Pc.Rr.Seal 1986-91, Ext.Bal., 153 T, 12.75 in.

 

'When Chevrolet went to the 1 piece rear main seal, they changed the shape of the mounting flange on the rear of the crankshaft. To offset this change, a small weight was added to the flywheel. These engines are still usually called internally balanced though, and they still use the same neutrally balanced dampeners.'
ok... apeiron.. were both one the same page i have the weight i just dont know where to put it... and i have to use the 400 balancer right?

 

There are three possibilities I can think of:

1. Your rotating assembly is internally balanced. It needs a stock 350 balancer and flexplate.

2. Your rotating assembly is externally balanced. It may need a stock 400 balancer. However since there were no factory 1 piece RMS 400 flywheels, it's difficult to say what flywheel you need.

3. Your rotating assembly is unbalanced or incorrectly balanced.

Since the original vendor doesn't seem to be able to tell you what you have, the only reliable option is to disassemble the engine and take your parts to a reputable machine shop for balancing.

Even if you had the weight to add to the flywheel, it's not just something you can expect to weld on yourself and have it work.

 

I think he has # 2, unless he paid thousands of $$$ for it. Most kits are externally balanced. Look up to my previous post, I actually found a part # from hayes for the correct flywheel.

REW, once again, what kind of balancer is on the motor now?

 

lo-tec, right now i have the 350 balancer on it but i also have a 400 balancer, ive tried them both, but with out the "extra" weight on the flywheel

 

Just not to confuse. I have a two piece rear seal and crank. Just trying to learn something while the subject is up.

 

lo-tec, apeiron, i do have a #2 i didnt spend mo $$$ for it, right now the motor has a 350 balancer on it

 

this is the add on weight from summit for a 2-piece RMS:

SES-3-60-11-026

 

If I was a betting man, I would put on the 400 balancer, and get the correct flywheel listed above. Call Hayes (or summit to see if they have something else that's the equivalent) to verify it b/c I'm getting my info from summit's website, but I think that's the solution.

 

i just want to thank every one that is helpin me. especially with all the part numbers and everything. the info is kinda "fuzzy" to me right now but il be sure to review it tommarow. but im not leaving yet, i just want everyone to know that i apprectaite their help

 

Here's a pic shaggy56:

 

Now why should I go to the neutral balance? Is something wrong with the external balanced parts?

 

lo-tec, apeiron- u guys have deff. helped out alot

 

Rew, one more thing. Once you put the 400 balancer on, VERIFY using a piston stop that the timing marks for TDC on the balancer and the timing chain cover coincide. A lot of times the timing pointer is for one balancer, and the groove in the balancer is for a different timing chain cover. One less thing to worry about down the road b/c they don't always line up.

 

Neutral balance is the goal, so that the engine isn't going to be tearing itself apart. Internal/external balance is just where the weight is placed to achieve neutral balance.

 

shaggy, na nothings wrong with an externally balanced assembly,it all depends on the kind of small block that you use. neutral balanced engines are only used for certain for certain vin# blocks