87 SBC 350 Internal / External balanced?? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-22-2004, 10:35 PM
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87 SBC 350 Internal / External balanced??

i have a 87 small block tbi 350 how can i tell if its internal or externaly balanced?

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Old 03-22-2004, 11:13 PM
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All small block chevy`s are internally balanced except the 400 small block. However, this is somewhat confusing, your 350 is internally balanced, but the rear of the crank is not, when chevy changed the crankshaft flange to perfectly round and 1 piece rear main seal in 1986, there was no where to put the needed counter weight to balance it, so the new flywheel/flexplate had extra weights added to balance it, but the harmonic balancer remained the same as previous models.
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Old 03-23-2004, 07:25 AM
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Quote:
Originally posted by DoubleVision
All small block chevy`s are internally balanced except the 400 small block. However, this is somewhat confusing, your 350 is internally balanced, but the rear of the crank is not, when chevy changed the crankshaft flange to perfectly round and 1 piece rear main seal in 1986, there was no where to put the needed counter weight to balance it, so the new flywheel/flexplate had extra weights added to balance it, but the harmonic balancer remained the same as previous models.

All small-block Chevys are NOT all internally balanced. 1985 and later small-blocks with the one-piece rear main seal are externally balanced on the flywheel end. Fortunately, the flywheel is not interchangeable between the interal and external types. You can tell the difference by determining if it is the one-piece rear seal type.


tom
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Old 03-23-2004, 08:38 AM
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what about the damper? thats the same all around?
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Old 03-23-2004, 08:57 AM
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The dampener is the same for the internally and externally balanced 305s and 350s. It is neutral balanced. You just have to watch the timing mark location.
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Old 03-23-2004, 11:12 AM
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If you`ll go back and read my post does it not say "but the rear of the crank is not, when chevy changed the crankshaft flange to perfectly round and 1 piece rear main seal in 1986, there was no where to put the needed counter weight to balance it, so the new flywheel/flexplate had extra weights added to balance it, but the harmonic balancer remained the same as previous models"
Now, what part of that is hard to understand? is it not the same thing you said in your post? is your answer any different than mine? so you just reanswered his question, I guess 2 answers are better than 1, especially when they say the same thing.
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Old 03-23-2004, 11:24 AM
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Quote:
Originally posted by DoubleVision
If you`ll go back and read my post does it not say "but the rear of the crank is not, when chevy changed the crankshaft flange to perfectly round and 1 piece rear main seal in 1986, there was no where to put the needed counter weight to balance it, so the new flywheel/flexplate had extra weights added to balance it, but the harmonic balancer remained the same as previous models"
Now, what part of that is hard to understand? is it not the same thing you said in your post? is your answer any different than mine? so you just reanswered his question, I guess 2 answers are better than 1, especially when they say the same thing.

Your answer was kind of confusing. A crank can't be both internally and externally balanced. In the case of the 85 and later one-piece rear main seal SBC's, they are externally balanced. I tried to make it a little clearer for the original thread starter, as he wanted to know simply if it was internal or external balanced.
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Old 03-23-2004, 03:55 PM
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punk1c5040
Reading this posting you should be in the Introduction to Hotrodding since you cannot understand two good explaination's.
Your answer's are well explained here and in the Introduction Forum, and in the Knowledge base.
What part of the answer don't you understand?
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Old 03-23-2004, 05:30 PM
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Tom I'm going to point out an error since you have stated it twice. SBC's went to a 1 piece rear main seal in 86, not 85.


Mike
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Old 03-23-2004, 08:25 PM
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Quote:
Originally posted by Ghetto Jet
Tom I'm going to point out an error since you have stated it twice. SBC's went to a 1 piece rear main seal in 86, not 85.


Mike
'

Actually, Mike, we both stand corrected. The one-piece rear main seal was introduced in 1985. The early 85 SBCs were 2 piece, while the later 85s were one piece. If you look in a gasket catalog (as I do every day), they state clearly that there were one and two piece designs for 1985. I still have here in the shop the one-piece designed block that I took out of my 1985 Chevy 4x4.

tom

Check this out:

http://www.pickproparts.com/PartsLis...ategoryID=5376
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Old 03-23-2004, 09:11 PM
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sorry i wasnt trying to 2nd guess anyone i just wanted to make sure before i buy a $100 damper ive gotten alot of answers before about other things that seemed to be right then when i asked what about this they changed a lil bit. no need to flip out or anything. thanks for the info tho
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Old 03-24-2004, 07:12 AM
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Thanks Tom, learn something new everyday.


Mike
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