Welcome to the North American Subaru Impreza Owners Club Wednesday April 16, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Built Motor Discussion

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 11-15-2012, 03:58 PM   #1
subadict
Scooby Newbie
 
Member#: 310017
Join Date: Feb 2012
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2008 WRX Hatch
obsidian black

Default What is a race preped head ?

Hi guys. I am trying to understand what a race preped head stands for. I want you to help me see which parts are different and the effect. What I mean is :
· I understand porting and port matching
· I understand that it will have heat resistant valve et valve seat (like titanium for the valves and beryllium for the seats)
· Probably a hi performance gasket to avoid any leaks (plus maybe a O’RING)
· Springs are going to be stiffer
· They’ll probably have more aggressive cams.
· And probably beefed up studs to keep the head from popping
What else ? And what will differentiate a “hi performance” head vs “racing”. Is there something else than CFM flow and head resistance that’s improved ?
Are the heads sold by mainstream companies like cosworth race heads or hi perf heads ?

Thanks alot.

If you have any reference, please post the link and I’ll read it. No bashing : I did not know how to find a precise answer.
* Registered users of the site do not see these ads.
subadict is offline   Reply With Quote
Old 11-15-2012, 04:18 PM   #2
djdalaney
Scooby Newbie
 
Member#: 301136
Join Date: Nov 2011
Default

Race anything generally just means it is not meant for street use. A race prepped head is most likely going to be built with high RPM in mind and wouldn't be the best choice for a street driven car. You often trade low end torque for high RPM power when machining/building heads. Without a specific example, that's pretty much all I can tell you.

Also, I believe O-rings are installed into the block, not the heads.
djdalaney is offline   Reply With Quote
Old 11-15-2012, 04:18 PM   #3
biodude
Scooby Specialist
 
Member#: 271720
Join Date: Jan 2011
Chapter/Region: Tri-State
Location: NEPA
Default

its a catch phrase to get you to spend more money.
biodude is offline   Reply With Quote
Old 11-15-2012, 04:21 PM   #4
subadict
Scooby Newbie
 
Member#: 310017
Join Date: Feb 2012
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2008 WRX Hatch
obsidian black

Default

Quote:
Originally Posted by djdalaney View Post
Race anything generally just means it is not meant for street use. A race prepped head is most likely going to be built with high RPM in mind and wouldn't be the best choice for a street driven car. You often trade low end torque for high RPM power when machining/building heads. Without a specific example, that's pretty much all I can tell you.
How is the high rpm optic going to be accomplish ? What kind of machining / changes are going to be made ?

Thanks by the way
subadict is offline   Reply With Quote
Old 11-15-2012, 05:26 PM   #5
djdalaney
Scooby Newbie
 
Member#: 301136
Join Date: Nov 2011
Default

Quote:
Originally Posted by subadict View Post
How is the high rpm optic going to be accomplish ? What kind of machining / changes are going to be made ?

Thanks by the way
Larger valves and larger ports mainly. These changes will decrease the velocity of the air, but allow it to flow a larger amount of air overall. The loss in air velocity will cause a loss in low end torque, but allow for more power in the top end due to more air flow.

Keep in mind, these are generalizations. I have no idea what head you are talking about, so I have no idea what was actually done or how it will perform.
djdalaney is offline   Reply With Quote
Old 11-15-2012, 06:13 PM   #6
drewvdw
Scooby Specialist
 
Member#: 255776
Join Date: Aug 2010
Chapter/Region: MWSOC
Location: Laramie, WY
Vehicle:
2010 LR WRX
MPS powered.

Default

^^^Suddenly the usefulness of individual throttle bodies is apparent to me.
drewvdw is offline   Reply With Quote
Old 11-15-2012, 11:52 PM   #7
subadict
Scooby Newbie
 
Member#: 310017
Join Date: Feb 2012
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2008 WRX Hatch
obsidian black

Default

Pretty clear. Thanks !
subadict is offline   Reply With Quote
Old 11-16-2012, 10:32 AM   #8
kellygnsd
Scooby Guru
 
Member#: 32669
Join Date: Feb 2003
Chapter/Region: SCIC
Location: Rancho C
Vehicle:
2007 2.34LR, EFR7670
LINK G4 hybrid STi

Default

"race prepped" means whatever the shop building the heads wants it to mean. Don't become preoccupied by key words and tricky phrases. Find out what you want done to your heads and commission a quality shop to get it done. After that you can call them whatever you want.
kellygnsd is offline   Reply With Quote
Old 11-16-2012, 02:11 PM   #9
subadict
Scooby Newbie
 
Member#: 310017
Join Date: Feb 2012
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2008 WRX Hatch
obsidian black

Default

Quote:
Originally Posted by kellygnsd View Post
"race prepped" means whatever the shop building the heads wants it to mean. Don't become preoccupied by key words and tricky phrases. Find out what you want done to your heads and commission a quality shop to get it done. After that you can call them whatever you want.
I'll ask the question differently : what could be done to the head to improve performance and what are the upsides / downsides to it ? I know a little bit about components as I said above but I don't know much about machining and the effects it'll have. It may be a newbe question but I cannot find any search word on google / nasioc that'll give me more than "race prepped" heads the way you stated it.

If you have any link to help me, it would be much appreciated.
subadict is offline   Reply With Quote
Old 11-16-2012, 03:25 PM   #10
biodude
Scooby Specialist
 
Member#: 271720
Join Date: Jan 2011
Chapter/Region: Tri-State
Location: NEPA
Default

Are you gathering info for a motor build or just for general knowledge?
If its for a build, state your goals and you will most likely get more specific replies as to the amount of work that is appropriate for your application

generally speaking, you want to do things to the heads that allow for smoother and more efficient air flow through the head. Valve jobs, bowl blending, porting and polishing, are examples of the types of work that is commonly done. I wont define each, they are common terms you can search for more detail.

On top of that there are things to you can do the the mechanisms themselves, such as changing cams, valves , valve springs, retainers etc. In my opinion this is where you begin to get into the 'raceprepped' category, once you begin to exceed the factory RPM and operating temps, you will need to start upgrading the hardware to meet those needs. For example if you wanted a higher RPM application, springs with higher seat pressures are needed and then along with that you need valves designed to withstand those higher pressures. Lighter spring retainers don't hurt either.

here is an old ad from ASF machine, with some pics of a mild and more extreme example of porting polishing and a multiangle valve job.
http://forums.nasioc.com/forums/show....php?t=2038614

there is some good reading in here by element tuning as to what they believe to be effective (scroll down for the head info)
http://elementtuning.com/competition-engines/

more on porting
http://forums.nasioc.com/forums/show....php?t=1728481

Last edited by biodude; 11-16-2012 at 03:45 PM.
biodude is offline   Reply With Quote
Old 11-17-2012, 12:59 PM   #11
subadict
Scooby Newbie
 
Member#: 310017
Join Date: Feb 2012
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2008 WRX Hatch
obsidian black

Default

Thanks alot, much appreciated !
subadict is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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
Forum Jump


All times are GMT -4. The time now is 09:08 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.