Welcome to the North American Subaru Impreza Owners Club Thursday March 28, 2024
Home Forums Images WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
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.







* As an Amazon Associate I earn from qualifying purchases. 
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 11-21-2006, 04:46 PM   #1
HamFist
Scooby Specialist
 
Member#: 2112
Join Date: Aug 2000
Chapter/Region: South East
Location: Below 900ft. Mach .9
Vehicle:
2000 Impreza 2.5RS
BRP

Default Techie question on head porting...

Some of my v8 head-porting knowledge has been thrown for a loop. The rule of thumb is to never modify the port floor because it is a stagnant flow area. Widen the port if possible, and grind at the roof of the port.

Well...the runner makes a slow 180-degree turn from the manifold into the head port, like a long "C" shape. The port "floor" at the plenum ends up being the port "roof" at the intake valve. WTF? I'm not going to just grind aimlessly with a dremel. Matching the intake/head ports isn't a big deal and it's a simple enough task. How do you get a little fancier than that and not hurt anything?
* Registered users of the site do not see these ads.
HamFist is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 11-23-2006, 11:32 AM   #2
no-coast-punk
Scooby Specialist
 
Member#: 49087
Join Date: Nov 2003
Chapter/Region: RMIC
Location: Inside your carnot cycle
Vehicle:
1998 RST V8 STi swap
'05 R6 '95 BMW V8 hotness

Default

Anything from the long (outer) edge of the "c" you described is kosher.
no-coast-punk is offline   Reply With Quote
Old 11-23-2006, 12:43 PM   #3
Homemade WRX
Scooby Guru
 
Member#: 33782
Join Date: Mar 2003
Chapter/Region: MAIC
Location: Milton Keynes, UK
Vehicle:
96 3MI Racing
search FIRST, then PM!!!

Default

yep...just don't make a pocket plenum shape at all...try and keep the diameter's even or a slight constant taper...regardless, no buldges that kill velocity and cause turbulence

just using putty to fill in areas on ports (using a B&S Animal head), I pick up significant gains 11.6-19.6% intake from @.150->.400 lift.
Exhaust gains were were just about 5% gains from .100-.450...it was killing flow because the port geometry was horrid and needed material removed.

Last edited by Homemade WRX; 11-23-2006 at 12:52 PM.
Homemade WRX is offline   Reply With Quote
Old 11-23-2006, 04:25 PM   #4
HamFist
Scooby Specialist
 
Member#: 2112
Join Date: Aug 2000
Chapter/Region: South East
Location: Below 900ft. Mach .9
Vehicle:
2000 Impreza 2.5RS
BRP

Default

Thanks guys . What kind of taper should the ports have? Stock, it looks like it starts smaller at the plenum and gets bigger at the valves. Switching to the 04-05 plenum like I plan, it still keeps the same kind of taper and shape. Getting inside the ports on that manifold past the bends would be virtually impossible anyway. But, I can still play with that taper a few inches into the ports. I've also considered a rouge polish on the intake and heads, but I think I can clean them up fine by hand.

Looking at the head as a nice chunk of operating metal from Fuji, I see nice size ports and valves, but it's under-cammed. Looking at my RPM limit, port size limits, and stock valve sizes (nice!), the stock cam is still puny! However, I'm not immediately jumping to the other end of the spectrum. Higher lift and "shorter" diration like a Delta is exactly what I'm after. More energy in this buildup is spent on trying to match the parts well instead of just "going bigger".

The SOHC design is a fine one to work with, IMO. High compression with good intake and exhaust flow should still be pretty interesting. It'll take some port and cam work to make power to 7500rpm, but it isn't impossible. Building these same heads for boost, I'd be using the same idea: portwork, stiffer springs, and better cams. You'd STILL have to spin it higher for bigger power anyway. The stock valves should do fine, too (I hope). Consider making consistent torque at a higher rpm, but not TOO high. I can turn the port flow and cams into an advantage if I can find the sweetspot of a combination. I'm not talking magic and 1,000hp, either. Spinning to 8k would be pointless without making power there. I think there's enough in the motor and heads to do that, so I want to see for myself.

Last edited by HamFist; 11-23-2006 at 04:34 PM.
HamFist 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Quick questions on head unit wiring harness jxkim Car Audio, Video & Security 12 04-09-2010 10:14 PM
Quick question on heads nomorepoison Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 6 04-05-2009 02:35 PM
Head Porting Question ImprezaRallystyle Normally Aspirated Powertrain 9 01-10-2006 09:02 AM
Ideas on my head porting project... posted in 2.0 too... bonzai Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo) 11 12-22-2005 03:34 PM
Quick question on Heads The_extreme Technical Forum Archive 2 07-17-2000 06:57 AM

All times are GMT -4. The time now is 03:01 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2024 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.

When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission
Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.