New Rods Arrived - New Crank Needed??? - 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
  #1 (permalink)  
Old 07-09-2013, 02:33 AM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,872
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
New Rods Arrived - New Crank Needed???

Ok guys, I ordered and received my new rods for the 400ci Sprint car motor today. The problem is, they are 83 grams heavier than my old rods that the crank was balanced to so my question is, would it be cheaper to buy a new crank rather than adding almost 3 ounces of mallory to the crank? The old rods were Lunati I-beams and the new rods are Oliver Parabolic beams. I do not want to grind on the new rods.

Thanks
Attached Thumbnails
Click image for larger version

Name:	SAM_1051.JPG
Views:	117
Size:	902.1 KB
ID:	75478  

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 07-09-2013, 01:24 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: 5,218
Wiki Edits: 9

Thanks: 101
Thanked 130 Times in 121 Posts
Unless you tell us how much your machinist wants to balance, and the price of whatever crank you would buy, no way for us to say.
__________________
Boost adds dignity to what would otherwise be a vulgar brawl...

Midnight Sun Street Rod Association
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-09-2013, 01:57 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 29
Posts: 8,720
Wiki Edits: 0

Thanks: 17
Thanked 289 Times in 269 Posts
How about your pistons? Are they lighter? Is the weight in the big or little end? It may not be that bad to balance or it may be.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 07-09-2013, 02:43 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,872
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Quote:
Originally Posted by ap72 View Post
How about your pistons? Are they lighter? Is the weight in the big or little end? It may not be that bad to balance or it may be.
My new pistons are 438gr compared to the old ones at 458gr. The new rods are heavier mostly on the big end. I am trying to weigh them all now but my scale is not reading what the box says they should be so I am doubtful on the old rod weights right now.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 07-09-2013, 04:27 PM
How fast is fast enough?
 
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 29
Posts: 8,720
Wiki Edits: 0

Thanks: 17
Thanked 289 Times in 269 Posts
If you have lighter pistons and the weight is in the big end and you have a lighter pin and ring pack even with a heavier big end you may need to lighten your crank. Too many variables.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 07-09-2013, 05:36 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Unlikely there will be a net loss of bobweight if the new rod's big end has the lions share of the added weight, given that 100% rotating (rod big end) is added to 50% reciprocating. WAG would be a couple ounces heavier bobweight. Might improve on this somewhat, given l/w pins if the original pins were standard weight.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 07-09-2013, 06:58 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,872
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Quote:
Originally Posted by cobalt327 View Post
Unlikely there will be a net loss of bobweight if the new rod's big end has the lions share of the added weight, given that 100% rotating (rod big end) is added to 50% reciprocating. WAG would be a couple ounces heavier bobweight. Might improve on this somewhat, given l/w pins if the original pins were standard weight.
I am learning about balancing and some terms are still fuzzy to me so bear with me while I try to understand and probably ask stupid questions. Here is what I had when the crank was balanced.

Pistons: 458gr
Pins: 144gr
Locks: 4gr
Rings: 58gr
BE Rod: 405gr
PE Rod: 172gr
Bearings: 40gr

Here is what I have now.

Pistons: 438gr
Pins: 130gr
Locks: 4gr
Rings:57gr
BE Rod:478.2gr
PE Rod:187.5
Bearings: 40gr

If someone can take these weights and figure out if my crank would need weight added is what I am looking to find out. If I need to weigh my crank to get to that figure, just let me know. I know the crank was balanced using the old setup. If weight needs added, I may just look at buying a new crank but hopefully that is a last resort.

Thanks guys
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 07-09-2013, 09:51 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,872
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
I must have made some enemies here, no one wants to reply?
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 07-09-2013, 10:06 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Looks like the bobweight will increase by about 63.5 g, or about 2-1/4 oz.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 07-09-2013, 10:29 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,872
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Quote:
Originally Posted by cobalt327 View Post
Looks like the bobweight will increase by about 63.5 g, or about 2-1/4 oz.
So I think you are saying that the crank will need 2-1/4 oz added to it to bring it close to balance?
If I was to buy a new crank, what bobweight would I need to be looking at to order and have balanced? I assume one would want to buy one that metal had to be removed instead of added?
Can you explain how to figure the bobweight? I'm still a little confused about that because there are two assemblies per crank throw?

Thanks
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 07-09-2013, 11:05 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
The figure I gave was one rod/piston assembly, so the bobweight would be twice that. The crank is now too light given the new weights.

Typically 100% of the rotating (rod big end) mass is added to 50% of the reciprocating. An allowance is given for oil that clings to the assembly. This is sometimes said to be 3-5 g for a SBC and is added to the rotating.

An example of what a balance card would look like (and will show you what you need to know regarding what weights are considered reciprocating and what are considered rotating):


Last edited by cobalt327; 07-09-2013 at 11:18 PM.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 07-09-2013, 11:21 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,872
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Quote:
Originally Posted by cobalt327 View Post
The figure I gave was one rod/piston assembly, so the bobweight would be twice that. The crank is now too light given the new weights.

Typically 100% of the rotating (rod big end) mass is added to 50% of the reciprocating. An allowance is given for oil that clings to the assembly. This is sometimes said to be 3-5 g for a SBC and is added to the rotating.

An example of what a balance card would look like (and will show you what you need to know regarding what weights are considered reciprocating and what are considered rotating):

Thanks Cobalt, it's starting to sink in a little. Would a 48lb crank be heavy enough to balance to these new values?
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 07-09-2013, 11:29 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by S10 Racer View Post
Thanks Cobalt, it's starting to sink in a little. Would a 48lb crank be heavy enough to balance to these new values?
You need to know what the crank bobweight "target" is estimated at. In your case, a crank w/a targeted B/W of >1857.5 g is called for provided that the values are correct on the card. I'd recommend double checking everything to be sure.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 07-09-2013, 11:38 PM
S10 Racer's Avatar
http://www.warsprints.com
 

Last journal entry: W.A.R. (Wingless Auto Racing) Sprint Car Racing
Last photo:
Join Date: Nov 2007
Location: At The Dirt Tracks
Age: 55
Posts: 1,872
Wiki Edits: 0

Thanks: 3
Thanked 57 Times in 52 Posts
Quote:
Originally Posted by cobalt327 View Post
You need to know what the crank bobweight "target" is estimated at. In your case, a crank w/a targeted B/W of >1857.5 g is called for provided that the values are correct on the card. I'd recommend double checking everything to be sure.
Thanks again. I know the rod values are correct, those numbers are from Oliver and is labeled on the box. I also know the piston weights are correct with what JE says they are because I weighed them and they were correct also. I am 100% sure all weights are correct.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 07-09-2013, 11:41 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
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
opening conecting rods to use Small jouornal rods with a large crank eatonde Engine 1 12-08-2008 04:22 PM
rods and crank camaroboy1991 Engine 0 05-01-2007 09:23 AM
rods and crank rustie Engine 3 09-07-2003 12:03 AM
crank and rods joes350truck1 Engine 2 03-12-2003 08:20 PM
how much will stock rods and crank take? nastynova Engine 7 12-30-2002 05:03 PM


All times are GMT -6. The time now is 11:47 PM.


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.