Balance confusion on 383... - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #16 (permalink)  
Old 08-03-2012, 07:46 AM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 7,696
Wiki Edits: 0

Thanks: 309
Thanked 740 Times in 711 Posts
thanks Mr P-body,I thought the high RPM process wass called under balance do to the other ends being slightly lighter,,,,,,I send clutch parts not to be balanced but to ensure the factory did a decent job, I also send my flex plate/flywheel for the same reason.I do take my engine builds above 6000 RPMs,even my 434 can rev to 7k.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 08-03-2012, 07:54 AM
zildjian4life218's Avatar
Listen and Learn
 
Last wiki edit: DIY junkyard electrical fan controller
Last journal entry: SBC 305 Twin Turbo
Last photo:
Join Date: Dec 2008
Location: WNY/Rochester, New York
Age: 25
Posts: 1,602
Wiki Edits: 7

Thanks: 44
Thanked 8 Times in 8 Posts
Quote:
Originally Posted by Mr. P-Body View Post
Most aftermarket forgings ARE "internal". Most castings are not. All of them can be "converted" using Mallory Metal (tungsten) as stated. Not cheap to "convert".

Many shops with a balancer have "on hand", stock 400 balancer and flexplate. We have a Pontiac flexplate that "lives" at the balance shop for this purpose.

The "bolt on" weight is popular among the 383 "crowd" because it allows the use of the "zero" flexplate or flywheel (they usually already have a 350 piece).

The clutch "cover" (pressure plate) is often attached during balancing for manual transmissions. Not used in automatic applications. With modern manufacturing techniques, this has become less an issue than it was 20 years ago.

Lastly, some "myths" about balancing. SAE "standards" are that the rotating assembly is balanced to within 1/2 of 1% of the total rotating "mass". In a 383, that amounts to about 28 grams. Most balance shops routinely balance to within 1 gram, FAR exceeding standards. The slight variations from using different "stock" balancers and flexplates/flywheels are not significant.

For higher revving engines (over 6,500), often "over-balance" is included. That's where the factor for the bob weight is changed from 50% (reciprocating) to a little higher percentage to offset the downward "thrust" under hard accelleration (engine speed, not car speed). High-end "big" engines usually have an over-balance of 4-5%.

FWIW

Jim
Awesome reply! He has an aftermarket cast crank that is externally balanced. So does he need the 400 harmonic balancer along with the flexplate?
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 08-03-2012, 08:16 AM
Registered User
 
Join Date: Dec 2009
Location: illinois
Posts: 373
Wiki Edits: 0

Thanks: 1
Thanked 32 Times in 32 Posts
Best reply I can give is ---check w/ the manufacturer..

dave
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 08-03-2012, 08:43 AM
bigdog7373's Avatar
Of course it's fast
 
Last photo:
Join Date: May 2010
Location: florida
Posts: 2,673
Wiki Edits: 0

Thanks: 13
Thanked 49 Times in 49 Posts
Quote:
Originally Posted by zildjian4life218 View Post
Awesome reply! He has an aftermarket cast crank that is externally balanced. So does he need the 400 harmonic balancer along with the flexplate?
Yes 400 flex plate and balancer. This has been said multiple times.
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 08-03-2012, 11:13 AM
68NovaSS's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Working with chromed bolts
Last journal entry: New to me T-Bucket
Last photo:
Join Date: Sep 2002
Location: Nine Mile Falls, Washington
Posts: 5,222
Wiki Edits: 9

Thanks: 102
Thanked 131 Times in 122 Posts
Quote:
Originally Posted by CNC BLOCKS NE View Post
OHHHHH yes it does as the 5.7 rod crank uses shorter counter weights and in most cases they are extrernally balanced.

A 6 inch rod crank uses bigger or taller counter weights and can be internally balanced.

Thats why all OEM 400's with their short rods are externally balanced.
I understand that, what I was referring to was using a 5.7/6.0 rod on an aftermarket stroked crank, say 383, using the appropriate pin height pistons. The poster didn't mention using a particular crank, be it OEM or aftermarket, just the rod being used.

What I don't understand is why you say a 5.7 rod crank is usually externally balanced, case in point, a stock, internally balanced 350 Chevy uses a 5.7 rod.
__________________
Boost adds dignity to what would otherwise be a vulgar brawl...

Midnight Sun Street Rod Association
Reply With Quote Quick reply to this message
  #21 (permalink)  
Old 08-03-2012, 12:13 PM
Registered User
 
Join Date: Nov 2011
Location: Virginia
Posts: 705
Wiki Edits: 0

Thanks: 0
Thanked 75 Times in 75 Posts
I've never seen any correlation between rod length and "type" of balancing. The application usually determines the type.

The flexplate or flywheel AND the balancer MUST be physically attached to the crankshaft during the process if "external". It's not uncommon to spin a crankshaft without the balancer and flexplate/flywheel if "internal". The balancer and flexplate/flywheel can be "spun" independently and checked for "zero".

Jim
Reply With Quote Quick reply to this message
  #22 (permalink)  
Old 08-03-2012, 01:01 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,745
Wiki Edits: 0

Thanks: 4
Thanked 416 Times in 359 Posts
Quote:
Originally Posted by zildjian4life218 View Post
Awesome reply! He has an aftermarket cast crank that is externally balanced. So does he need the 400 harmonic balancer along with the flexplate?
Yes!

The aftermarket 383 stroker cranks that use external balance are made to also use the 400's damper up front and flywheel or flexplate at the rear.

Bogie
Reply With Quote Quick reply to this message
  #23 (permalink)  
Old 08-03-2012, 04:33 PM
CNC BLOCKS NE's Avatar
CNC Blocks Northeast
 
Last photo:
Join Date: Sep 2006
Location: NORTHEAST
Age: 54
Posts: 1,433
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 17 Posts
Quote:
Originally Posted by 68NovaSS View Post
I understand that, what I was referring to was using a 5.7/6.0 rod on an aftermarket stroked crank, say 383, using the appropriate pin height pistons. The poster didn't mention using a particular crank, be it OEM or aftermarket, just the rod being used.

What I don't understand is why you say a 5.7 rod crank is usually externally balanced, case in point, a stock, internally balanced 350 Chevy uses a 5.7 rod.

I think the OP is talking about a 3.750 stroke not a 3.480 stroke big differance between the two.
Reply With Quote Quick reply to this message
  #24 (permalink)  
Old 08-03-2012, 04:49 PM
68NovaSS's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Working with chromed bolts
Last journal entry: New to me T-Bucket
Last photo:
Join Date: Sep 2002
Location: Nine Mile Falls, Washington
Posts: 5,222
Wiki Edits: 9

Thanks: 102
Thanked 131 Times in 122 Posts
Quote:
Originally Posted by CNC BLOCKS NE View Post
I think the OP is talking about a 3.750 stroke not a 3.480 stroke big differance between the two.
I have a 3.750 stroke aftermarket crank in my 383 blower car, with 5.7 rods, and it's internally balanced, it can go either way, no question about that. I'll assume from your post, an OEM 400 crank doesn't lend itself to internally balancing.
__________________
Boost adds dignity to what would otherwise be a vulgar brawl...

Midnight Sun Street Rod Association
Reply With Quote Quick reply to this message
  #25 (permalink)  
Old 08-04-2012, 05:05 AM
CNC BLOCKS NE's Avatar
CNC Blocks Northeast
 
Last photo:
Join Date: Sep 2006
Location: NORTHEAST
Age: 54
Posts: 1,433
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 17 Posts
Quote:
Originally Posted by 68NovaSS View Post
I have a 3.750 stroke aftermarket crank in my 383 blower car, with 5.7 rods, and it's internally balanced, it can go either way, no question about that. I'll assume from your post, an OEM 400 crank doesn't lend itself to internally balancing.
I have internally balanced 400 cranks its very costly but it was for a cheater circle track engine.

I have seen a few 5.7 rod cranks that will internally balance but most seem to be internally.

All the strokers I build I use 6 inch rods better rod ratio, less piston hanging out of the borre at BDC, liter piston, internally balance.
Reply With Quote Quick reply to this message
  #26 (permalink)  
Old 08-04-2012, 09:30 AM
Registered User
 
Join Date: Dec 2009
Location: illinois
Posts: 373
Wiki Edits: 0

Thanks: 1
Thanked 32 Times in 32 Posts
Bogie , Sorry , but all aftermarket are not external/external ! Strokermotors lists 3 different scenario's- Int/Int-Int/Ext - Ext/Ext. Most,but not all 6" rod listings are Int. Most , but not all 5.7" rod listings are int..

dave
Reply With Quote Quick reply to this message
  #27 (permalink)  
Old 08-06-2012, 11:24 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,745
Wiki Edits: 0

Thanks: 4
Thanked 416 Times in 359 Posts
Quote:
Originally Posted by 2old2fast View Post
Bogie , Sorry , but all aftermarket are not external/external ! Strokermotors lists 3 different scenario's- Int/Int-Int/Ext - Ext/Ext. Most,but not all 6" rod listings are Int. Most , but not all 5.7" rod listings are int..

dave
Dave, I believe I used the term "that use external balance" the remainder being. "use the 400 balancer". I was not intending to discuss the effects of 6 inch rods versus 5.7 and their effect on crank balance only to clarify that the external balance 383 stroker crank is intended to use, or at least start from, the 400 damper and flywheel or flexplate.

An internal balanced 383 stroker will use the neutral balanced 350 damper and flywheel/flexplate as the best starting point. This will hold true whether the crank began life as an internally balanced with 6 inch rods or and externally balanced with 5.7 inch rods that is forced by the use of Mallory Metal to become an internally balanced crank. Which is to say that the choice of external or internal balanced damper and flywheel/flexplate needs to match the choice of external or internal balance crank.

I am not a big fan of externally balanced engines, while the crankshaft as a whole rotates on center just as it does when internally balanced; there remains a long distance between out-of-plane forces which results in bending moments along the crankshaft. Evidence of these can be seen in the main bearings when the engine is opened up you will typically see bearing shells that exhibit inconsistent wear both within the diameter and across the width. Given that the engine builder needs to understand how much of this is flexing of the crankshaft between bearing bays and how much is lack of alignment through the bearing bores.

Internal balancing eases this situation somewhat but doesn't entirely make it go away. Crankshafts do funny things which is one reason why there is so much counterweight on the ends compared to the inboard throws. Some if this is simply space related where the inboard throws don't have enough space for full counterbalance and some is the tendency of the crank to want to orbit its ends instead of just rotate them on a center. So the big counterweights are king of pulling the ends back to the plane of rotation. The center two throws usually don't have counterweights as all but depend upon their masses in opposition to achieve balance. The problem with this is that there is a lever arm distance between these throws that results is the loads being offset by that distance, this then wants to bend the crank between the number two and four main with number three being a pivot point. This is the reason why 4 bolt and cross bolted mains are found in the middle of high performance blocks. This condition can be relieved by the use of counter weights on the inboard side of throws two and three. But for a street engine this adds cost where it typically isn't necessary although the old Ford Y block crank was weighted here. The extra weight slows crankshaft acceleration so it's usually isnít found on drag race engines. It is rather commonly found on NASCAR cup engines where constant high loading on the crank requires better bearing bay to bay balance for reduced wear on bearings and less concentrated loading into the block at this point combined with a reduced need for absolute maximum rates of crankshaft acceleration as found in drag engines. There are of course exceptions where some builders feel the aftermarket competition block and crankshaft are sufficiently strong enough to sustain these loads for the needed periods of time and they want the lighter faster to accelerate crankshaft that is more akin to what the drag racers would use.

Bogie
Reply With Quote Quick reply to this message
  #28 (permalink)  
Old 08-06-2012, 01:53 PM
Registered User
 
Join Date: Nov 2004
Location: California
Age: 67
Posts: 828
Wiki Edits: 0

Thanks: 27
Thanked 21 Times in 19 Posts
68 NovaSS and BigDog7373
Thanks for enlightening me. When I bought my parts (back 10-12 years ago) the market was more limited, and the vast majority of internal balanced 383 Stroker cranks required the 6.0 rods. This was for the reason that CNC Northeast mentioned, or at least I thought and continue to believe. The Mallory Metal is, of course, an answer for almost anything remotely within reason. But, it is very expensive. And the more you need, the more expensive it becomes. As a result of your posts I went to the Eagle and Scat sites and found a broad assortment of cranks and kits set up for internal balance with 5.7 rods. I have to presume this requires the use of their specified (or somewhat akin) pistons, to clear the counterweights.

Anyway, again, thanks for enlightening me . . And CNC Northeast -- I still agree that for an internally balanced 383 it probably makes most sense to use 6 inch rods . . but it seems there are ways to use those 5.7 inch rods now in an internally balanced 383, without the need for Mallory Metal. I'm sure you knew that already, but I (for one) feel enlightened.

PatM
Reply With Quote Quick reply to this message
  #29 (permalink)  
Old 08-06-2012, 02:16 PM
Registered User
 
Last photo:
Join Date: Jul 2004
Location: At Speed
Age: 51
Posts: 1,336
Wiki Edits: 0

Thanks: 2
Thanked 27 Times in 27 Posts
There can be a big difference in weight between different rods and pistons, too. Lighter parts make it easier to balance with smaller counterweights.
Reply With Quote Quick reply to this message
  #30 (permalink)  
Old 08-06-2012, 02:44 PM
Registered User
 
Join Date: Nov 2004
Location: California
Age: 67
Posts: 828
Wiki Edits: 0

Thanks: 27
Thanked 21 Times in 19 Posts
lmsport
Yeah, so true. My machinist/balancer had to remove a lot of material from the counterweights because of the very light (Lunati Streetrace, no longer available, I think) rods, pistons and pins that I selected. His comment after completing the balance was the the engine should be a "zinger", meaning quick to build up revs. . . . . I hadn't mentioned it to him, but that was exactly what the goal was. Now that I think of it, when I gave him the crankshaft and the value for the bobweights, I don't think he believed me. He asked me to bring in the parts. So I brought in one piston, one pin, spirolocks, one rod, one bearing and a ring set, all previously static balanced. I don't recall the exact bobweight (I think 1668, but I can't swear) but his calcs came out within 1 gm of the value I had given him.

Pat
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
chevy 383 balance Icelander Engine 2 03-28-2008 06:00 PM
383 balance funbiz99 Engine 21 03-14-2007 09:12 PM
383 stroker balance CAMARO Engine 23 03-14-2007 08:38 PM
383 Balance Qurstion funbiz99 Engine 4 02-27-2007 04:45 AM
383 Balance Question crusherdbuzz Engine 7 04-29-2006 11:04 PM


All times are GMT -6. The time now is 01:43 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.