LS5 balancer

[baxsom]

what is the correct size of a 454 LS5 balancer. I decided to go ahead and order a new one to replace my beat up one since i have it off anyway.

i got an oem replacement from napa.
it was 8"
the one that came off of it was 7"

the 7" balancers were for the 427 right.
interesting since the car had 427 heads as well.

casting# says that the engine is a 454 like it is supposed to but now i am wondering if i need to order another 427 balancer since there is a difference in balancing right?
internal vs external?
just by looking how do i tell the difference between internal and external balance

will there be an issue with the 8"

 

[Hib Halverson]

427 is internal balanced, 454 is external.

A 27 balancer is not going to work on a 54 nor will the opposite work.

I don't remember ever seeing a 7" balancer on a Corvette 454, but I sppose it's possible.

Is the balancer that came off int. or ext. balance. Look at the back of it and see if there are obvious weighted parts of the hub.

 

[baxsom]

427 is internal balanced, 454 is external.

A 27 balancer is not going to work on a 54 nor will the opposite work.

I don't remember ever seeing a 7" balancer on a Corvette 454, but I sppose it's possible.

Is the balancer that came off int. or ext. balance. Look at the back of it and see if there are obvious weighted parts of the hub.

this is what came off it

it is just shy of 7 inches in diameter. there are no holes drilled in it anywhere. just a dimple on the front. total weight is 10.5lbs.

if it were not for the crack right where the key goes in, i would just reuse it. of course i would be intersted just for novelty sake as to what a 10lbs balancer spinning 6K would do as it came apart but not enough to pay for it.

block is definetly a 454 block,
casting number is 454 and pistons are 4.58 (30 over) in diamter

when i checked the casting number on the heads that i took off they were a 66 427/390 casting.

 

[Crimson Thunder]

Are you sure somebody didn't swap in a 427 crank into your 454 block? Did you measure the stroke when you had a head off?

 

[baxsom]

i didnt even think to measure it.
considering all of the other 427 parts i have found on the car, it wouldnt surprise me.

any way to tell.

it is definetly internally balanced though
neither the balancer or flywheel has counter weights

i found the GM part number on the back of the 7" balancer and found a NOS replacement 3860060.

 

[gmjunkie]

I bought a new one from Chevrolet when I built my LS6,my wholesale cost was around $90.00!! Thats been 8-9 years though!!:L

 

[baxsom]

yeah thats about the cost of the one i found.

its a gamble being on ebay and all but i know that particular one works (unless someone along the way modified the cracked one i took off anyway)

 

[Hib Halverson]

I know you said the casting number was for a 454, but with so many 427 parts on the engine, should we double check?

What's the CN of the block?

 

[baxsom]

I know you said the casting number was for a 454, but with so many 427 parts on the engine, should we double check?

What's the CN of the block?

on the block drivers side, right where the engine mounts to the tranny
3999289 and then something that looks like a copyright C emblem

from the website
Big Block Chevy Engine Parts Identification
it says that is for a 70-74 2 bolt 454

(its a 4 bolt btw)

there is no vin, the vin plate is completely blank no marks that would indicate machining or filing

 

[TimAT]

THIS is a 454 balancer. Note the chunk of iron cast into it for external balance.
454 Harmonic balancer pictures from hobbies & interests photos on webshots

 

[baxsom]

yeah.
thats not what came off of it.
i ordered a new 67 427/390 balancer and it is identical to the cracked one that came off.
you can see on the pic that i posted that there was no offset weight.

 

[TimAT]

Bax, have you got the pan off so you can see a casting number on the crank? Take some pictures of the front throw right behind the #1 main bearing journal.

 

[baxsom]

Bax, have you got the pan off so you can see a casting number on the crank? Take some pictures of the front throw right behind the #1 main bearing journal.

damn, i already put the pan back on.

i know that the one you are talking about it has 3 deep drilled holes into it.

 

[TimAT]

Just from that little bit of info, I'd say your crank is internal balance. I don't recall GM ever drilling more than one hole into a crank for balance. Not that GM didn't, I just don't remember ever seeing one.