External Balancing - 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
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 12-12-2010, 09:01 PM
Registered User
Join Date: Nov 2010
Location: Columbia, SC
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
External Balancing

I have an externally balanced 383 chevy rotating assembly. Question- would you feel safe spinning it to 6500. Bolts are ARP throughout. If not, why so.

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 12-12-2010, 09:48 PM
327NUT's Avatar
Registered User
Last photo:
Join Date: Dec 2004
Location: So. Utah
Age: 70
Posts: 3,414
Wiki Edits: 0

Thanks: 0
Thanked 123 Times in 110 Posts
Without knowing the rest of the parts list i.e. cast...forged? how it was built and who built it I would say no. Now If a knowedgeable person built it with the right combination of parts and it was balanced and tuned properly then yes it would be safe to 6500.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 12-13-2010, 01:09 AM
ericnova72's Avatar
More for Less Racer
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 50
Posts: 13,262
Wiki Edits: 0

Thanks: 140
Thanked 1,761 Times in 1,493 Posts
Put together with properly clearanced parts and with ARP hardware... 7500 rpm wouldn't really bother me, lots of folks have done it including myself and friends for drag race or street/strip use. Circle track use would make me think twice but 6500 rpm still wouldn't bother me there.

Internal balance of "normally" external balance assemblies has been a little over-emphasised the last 5 years or so, 100,000's of engines were built external balance before this trend became so in vogue, and we didn't worry about it back then, and stuff still ran good and stayed together.

I don't see it being a necessity until you get over the 7800-8000 rpm drag level or 7400-ish rpm circle track level.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 12-13-2010, 10:32 AM
Registered User
Join Date: Apr 2007
Posts: 9,614
Wiki Edits: 0

Thanks: 18
Thanked 228 Times in 184 Posts
Originally Posted by 803Paul
I have an externally balanced 383 chevy rotating assembly. Question- would you feel safe spinning it to 6500. Bolts are ARP throughout. If not, why so.
Depends on the crank. Cast no, Forged yes. One has to keep in mind that while the whole assembly is in balance, there are local differences that want to cause the shaft in those areas to run other than in its machined centers. This results in local bending moments which castings being more brittle really don't like. A high quality damper is a must as these local distortions run in and out they put vibrations into the shaft that if they gang up can become quite destructive.

This is fine for a drag or short track engine, if you're thinking of long term survival at these revs on a road course, an internally balanced crank would be a better way to go, especially with a production block as these aren't as beefy as Bow-Tie or aftermarket components which better tolerate externally balanced cranks.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply

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:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


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
Internal vs. External Balance 68NovaSS Engine 17 06-12-2010 06:57 PM
chevy SB external oil pump? jeepers creepers Engine 6 09-09-2009 05:04 PM
Balancing Question S10 Racer Engine 11 06-05-2008 06:43 PM
Internal... External... Balance that 383!! KSailer77 Engine 8 06-09-2007 08:22 AM
383 external balance question ljjjrome Engine 24 01-18-2007 08:31 PM

All times are GMT -6. The time now is 01:19 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.