Sbc firing order changes? - 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> General Rodding Tech
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 02-05-2012, 10:44 PM
Registered User
 

Last journal entry: Starting the build, 333ci chev, 195 cc jegs heads
Last photo:
Join Date: Mar 2009
Location: anoka mn
Posts: 375
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sbc firing order changes?

I happen to be doing some reading recently on (ferrari, datsun L6 motors etc) v12s and L6s and angle of crankshafts etc. I came across some info on why v12s and L6 motors are "naturally balanced". Apparently aside from crankshaft angles uses of flat plane crankshafts, one of the biggest factors was the firing order of the engines and how that then affects the throw of each cylinder balance the other piston throws (in basic terms).

So - that being said, theoretically, what firing order would a sbc need to have to be balance like these motors?

Blight~

on a side note
http://speedtalk.com/forum/viewtopic.php?f=1&t=130

    Advertisement

Last edited by blight; 02-05-2012 at 10:59 PM.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 02-05-2012, 11:01 PM
Registered User
 

Last journal entry: Starting the build, 333ci chev, 195 cc jegs heads
Last photo:
Join Date: Mar 2009
Location: anoka mn
Posts: 375
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Why would this be moved to general rodding tech? This is particular about engines- where this originally was...
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 02-06-2012, 07:54 AM
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
My understanding is the firing order of a 90 V8 compromise between breathing and torsional stress. There are three that are most often used:

1-8-4-3-6-5-7-2 (Mopar, Chevy, Ford pre-~'70)
1-8-7-3-6-5-4-2 ("4/7 swap")
1-8-7-2-6-5-4-3 (Ford ~'70-up, Chev LS)

Regardless of which of these firing orders are used, there will be two cylinders on each bank firing consecutively and once the two cylinders will be adjacent cylinders that fire consecutively.

I hope Old Bogie or Techinspector1 notices this thread and fills in the many blanks/details.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 02-06-2012, 09:14 AM
Registered User
 

Last journal entry: Starting the build, 333ci chev, 195 cc jegs heads
Last photo:
Join Date: Mar 2009
Location: anoka mn
Posts: 375
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
What would be the most balance set of pulses then? Most as in the closest to being balanced.
v8s
1-8-4-3-6-5-7-21988 Chrysler Fifth Avenue, Chevrolet Small-Block engine
1-8-7-2-6-5-4-3GM LS engine, Toyota UZ engine
1-3-7-2-6-5-4-8Porsche 928, Ford Modular engine, 5.0 HO
1-5-4-8-7-2-6-3 BMW S65
1-8-7-3-6-5-4-2Nissan VK engine
1-5-4-2-6-3-7-8 Ford Windsor engine
1-5-6-3-4-2-7-8 Cadillac V8 engine 368, 425, 472, 500 only
1-5-3-7-4-8-2-6 Ferrari V8's, (all are flat-plane crank)
1-2-7-8-4-5-6-3Holden V8
1-2-7-3-4-5-6-8 Cadillac Northstar Engine

v12s
1-7-5-11-3-9-6-12-2-8-4-10 2001 Ferrari 456M GT V12
1-7-4-10-2-8-6-12-3-9-5-11 1997 Lamborghini Diablo VT

Last edited by blight; 02-06-2012 at 09:34 AM.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 02-06-2012, 09:37 AM
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 way the SBC was originally designed has served that engine well for a long time and that's what all the aftermarket and production cranks are designed around. Since there's basically only the 4/7 swap to change to (unless you were starting w/a blank sheet or were going to use a 180 degree crank or split rod journals like even/semi-even fire V6 engines use), I'd leave it be.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 02-06-2012, 09:43 AM
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 blight
What would be the most balance set of pulses then? Most as in the closest to being balanced.
v8s
1-8-4-3-6-5-7-21988 Chrysler Fifth Avenue, Chevrolet Small-Block engine
1-8-7-2-6-5-4-3GM LS engine, Toyota UZ engine
1-3-7-2-6-5-4-8Porsche 928, Ford Modular engine, 5.0 HO
1-5-4-8-7-2-6-3 BMW S65
1-8-7-3-6-5-4-2Nissan VK engine
1-5-4-2-6-3-7-8 Ford Windsor engine
1-5-6-3-4-2-7-8 Cadillac V8 engine 368, 425, 472, 500 only
1-5-3-7-4-8-2-6 Ferrari V8's, (all are flat-plane crank)
1-2-7-8-4-5-6-3Holden V8
1-2-7-3-4-5-6-8 Cadillac Northstar Engine

v12s
1-7-5-11-3-9-6-12-2-8-4-10 2001 Ferrari 456M GT V12
1-7-4-10-2-8-6-12-3-9-5-11 1997 Lamborghini Diablo VT
When comparing the firing orders, be sure you take the way the cylinders are numbered into consideration.

As an example the Ford "1-5-4-2-6-3-7-8" is (when looked at using Chevy cylinder numbering) is the same as Chevy: 1-8-4-3-6-5-7-2.

The Northstar, IIRC, has #1 on the left side looking at the "front" of the engine, driver side transversly.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 02-06-2012, 12:36 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,688
Wiki Edits: 0

Thanks: 3
Thanked 403 Times in 348 Posts
Quote:
Originally Posted by blight
I happen to be doing some reading recently on (ferrari, datsun L6 motors etc) v12s and L6s and angle of crankshafts etc. I came across some info on why v12s and L6 motors are "naturally balanced". Apparently aside from crankshaft angles uses of flat plane crankshafts, one of the biggest factors was the firing order of the engines and how that then affects the throw of each cylinder balance the other piston throws (in basic terms).

So - that being said, theoretically, what firing order would a sbc need to have to be balance like these motors?

Blight~

on a side note
http://speedtalk.com/forum/viewtopic.php?f=1&t=130
Has nothing to do with firing order, the issue is of secondary balance which is having a cylinder's parts in motion off setting the actions of another. In this case an inline 6 or a 60, 120,180 degree V12 have such a situation because of block and crankshaft configuration.

A 90 degree V8 always has a little secondary vib, there's no way around it by juggling firing orders or anything else short of a counter balance shaft.

The I6, V12 and V8 have primary balance which is the rotational masses in balance. The secondary balance the is motion of the reciprocating parts. Their motions are not linear with crankshaft degrees. Each piston with the rod small ends and some amount of shank have different rates of acceleration as the crankshaft turns and the reciprocating parts move up and down rather than round and round as the crank and big end of the rod do. For secondary balance there needs to be a combination of two cylinders worth of rods and pistons that are doing exactly the same acceleration but in reverse directions of motion to each other.

By "acceleration" I'm talking the different speeds the piston and upper rod travel at even when the engine itself is held to a constant RPM. This has nothing to do with speeding or slowing the crankshaft.

It's all in high school trigonometry class. Think how much more fun it would be with engines for examples instead of dry memorization of trig functions and the doing of inane problems. The SAE keeps bugging me to become a math mentor, maybe I should. That would be one bizarre math class.


Bogie
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 02-06-2012, 01:07 PM
Registered User
 
Join Date: Nov 2004
Location: California
Age: 67
Posts: 828
Wiki Edits: 0

Thanks: 27
Thanked 21 Times in 19 Posts
If you do it, please do it online so that folks NOT in the great NorthWest can share in the fun.

Pat
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 02-06-2012, 08:08 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,688
Wiki Edits: 0

Thanks: 3
Thanked 403 Times in 348 Posts
Quote:
Originally Posted by PatM
If you do it, please do it online so that folks NOT in the great NorthWest can share in the fun.

Pat
More detail than I know just yet.

Using your response to expose the guys to the Buick Nailhead firing order. This is the same cylinder counting as the Chev but a way different firing order of 1-2-7-8-4-5-6-3.

OK I'm locking up and going home.

Bogie
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 02-06-2012, 08:13 PM
Registered User
 

Last journal entry: Starting the build, 333ci chev, 195 cc jegs heads
Last photo:
Join Date: Mar 2009
Location: anoka mn
Posts: 375
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
what is your opinion on 4-7 swaps etc?
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 02-07-2012, 10:02 AM
1971BB427's Avatar
Registered User
 

Last journal entry: Latest changes
Last photo:
Join Date: Dec 2010
Location: Portland
Posts: 1,465
Wiki Edits: 0

Thanks: 12
Thanked 217 Times in 188 Posts
The 4-7 swap is what some racers in the 60's changed to in an effort to smooth up the engine and get a litle higher rpm's. It involves having a cam ground to this configuration, or buying one. (they are available)
The 4-7 swap is in my opinion a lot of work and money for very small gains, and not worth the time and money.
Reply With Quote Quick reply to this message

Recent General Rodding Tech 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
64 Merc cyclinder order/firing order 64merc Engine 1 07-11-2007 08:17 AM
firing order 88chevy Engine 9 04-19-2007 07:21 PM
Firing Order 67 Hugger Engine 2 06-30-2005 06:26 AM
Firing order raidmagic Hotrodding Basics 3 11-02-2004 06:53 AM
Firing Order? TonyMac Engine 7 07-11-2003 10:06 PM


All times are GMT -6. The time now is 06:42 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.