detonation - 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 08-13-2010, 09:44 PM
Registered User
 
Join Date: Aug 2010
Location: tennessee
Posts: 15
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
detonation

I originally thought my heads had around 72 cc chambers they are phaseII bowties ive learned they hace 64 cc chambers but mine have been milled so they may be less than 60 cc now an i prolly have around 11 to 1 instead of the 9 to 1 i thought i had, i run 93 octane and have never noticed any spark knock i find that hard to believe with steel heads an 11 to 1, i run 36 degree total timing ,maybe my pointers way off ? ,How noticeable is detonation in a loud car turnin 6000 ? next time at the track would it be safe to bump my timing up a lil at a time till until i notice somthing or slow down an not worry about messin somthin up ?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 08-13-2010, 11:01 PM
Registered User
 
Join Date: Aug 2010
Location: OKLAHOMA
Posts: 6
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sound like you are running the same thing that I am running in my truck. It was a must for me to run the 93 octane. I messed up my first build in 3 days buy running cheap gas. As far as timing goes I just had to play with it till it run right at rpm.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 08-13-2010, 11:18 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,153
Wiki Edits: 0

Thanks: 5
Thanked 380 Times in 374 Posts
if you want a informed comment on your motor you might want to inform us as to what you got these heads bolted onto.

What is the real compression ratio? deck height gasket volume, dome volume etc etc.
Just cause your heads are milled does not mean they were 64cc to start with or are 60cc now.

You're assuming a lot. Just because you made it down the drag strip on that day does not mean you are ok on another day when condition are different, or are going to be ok in traffic on a hot day.

Check the TDC pointer using a piston stop.
You will not hear detonation with loud exhaust.

While it is possible to run 11:1 cr on the street on pump gas under ideal favorable conditions, conditions are never always ideal or favorable all the time and it only takes once under less than ideal conditions to cause enough detonation and bust a piston ring land.
When this happens, you won't see it coming.
In other words if you tune it and run it right on the edge, sooner or later your luck will run out.

Knowing that your engine has a high compression ratio and you are going to run it hard at the track (or on the street), it is fool hardy to short the motor on fuel octane.
Shorting such a motor on fuel octane is like filling the crank case with the worst crap motor oil just cause its cheaper.
For 11:1 cr you want a real R+M/2 octane of 98 to 102.
You can mix premimum 92 gas with 110 unleaded race gas to achieve this or run 100 octane fuel. Octane (ability to resist knock) is insurance against engine destroying damage caused by detonation and or preignition.
Ya get what you pay for.

In a high compression engine:

Think of fuel octane and extra cost associated with it, like car insurance, you don;t need it until you need it, then you really need it and are glad you got it.
How close to the edge can you afford to run?

Last edited by F-BIRD'88; 08-13-2010 at 11:43 PM.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 08-14-2010, 06:12 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 whathaveigotinto
I originally thought my heads had around 72 cc chambers they are phaseII bowties ive learned they hace 64 cc chambers but mine have been milled so they may be less than 60 cc now an i prolly have around 11 to 1 instead of the 9 to 1 i thought i had, i run 93 octane and have never noticed any spark knock i find that hard to believe with steel heads an 11 to 1, i run 36 degree total timing ,maybe my pointers way off ? ,How noticeable is detonation in a loud car turnin 6000 ? next time at the track would it be safe to bump my timing up a lil at a time till until i notice somthing or slow down an not worry about messin somthin up ?
Use the following to determine if the timing tab/mark is accurate:

DETERMINE TDC. Then MAKE A TIMING TAPE so you can see what the total timing, etc. is w/o needing a dial back timing light- which may or may not be accurate itself.

The problem w/doing track testing to set the timing, is that you really don't know where you are starting at. One run under severe, unheard detonation can ruin an engine- so you need to start at a safe timing setting and work up from there.
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:
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
Detonation... yttaf Engine 20 08-03-2010 07:19 PM
Detonation 351c Help agtpony@hotmail.com Engine 2 09-28-2006 11:18 AM
detonation resistance, short or long rods? Old School Nut Engine 34 12-31-2004 12:23 AM
Octane, Ignition, Cr & Detonation sharp21 Engine 14 12-25-2004 10:08 PM
Detonation? lluciano77 Engine 3 11-12-2003 10:04 PM


All times are GMT -6. The time now is 07:16 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.