Welcome to the North American Subaru Impreza Owners Club Saturday August 2, 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 > Normally Aspirated Powertrain

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 07-08-2002, 04:47 PM   #1
Corey
Scooby Specialist
 
Member#: 618
Join Date: Dec 1999
Location: PA, USA
Vehicle:
2000 2.5 RS #89 STS
MODERacing / Bridgestone

Default More power to be had with tighter valve lash?

While doing my 2nd valve lash adjustment since installing the COBB street cams I started thinking ... If the valve lash is adjusted to be tighter than factory, it would provide more lift, and more airflow... maybe a few extra "free" HP also?

Obviously you would have to be careful not to make it too tight or your valves wouldn't close completely.

Could this be some free power to be had for all those running on stock cams?

I'd like to hear the opinions of some of the experts on this, maybe I'm way off

Corey #89 SM
* Registered users of the site do not see these ads.
Corey is offline   Reply With Quote
Old 07-08-2002, 07:34 PM   #2
ColinL
Scooby Guru
 
Member#: 114
Join Date: Jul 1999
Chapter/Region: MWSOC
Location: Wichita, KS and Whoring, OT
Vehicle:
'03 Evo, Rice White
'01 Erion CBR 929

Default

you will probably experience excessive cam wear if the lash is less than the minimum factory spec, which is the (IIRC) .008" and .010" listed under the hood and in the FSM.

beyond that point, then yeah maybe the valves won't close all the way. probably not, you'll probably just wear the cam and rocker tips.
ColinL is offline   Reply With Quote
Old 07-08-2002, 11:37 PM   #3
Patrick Olsen
NASIOC Supporter
 
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
Vehicle:
1997 Legacy 2.5GT
QuickSilver Metallic

Default

Corey - What specs are you using to set the valve lash with your street cams? Of course, it's probably different since you have a SOHC and I have a DOHC, but I'll ask anyway. I'm having the dealer check/adjust mine on Thursday, and I need to find out from Cobb if there are any special specs to use, or if the factory specs are good to go.

Pat Olsen
'97 Legacy 2.5GT sedan
Patrick Olsen is offline   Reply With Quote
Old 07-09-2002, 12:58 AM   #4
Scubaru
Scooby Specialist
 
Member#: 1530
Join Date: May 2000
Location: In Front Of You!
Default

I always thought you wanted to set your valve lash to the ''loose" side of the adjustment spectrum to free up the valve train from binding and excessive wear on your cams. Or the thats what I've learned building motorcycle motors. We just had to monitor valve clearances more often though -Scu
Scubaru is offline   Reply With Quote
Old 07-09-2002, 02:27 AM   #5
HndaTch627
Scooby Guru
 
Member#: 6551
Join Date: May 2001
Chapter/Region: MWSOC
Location: Carol Stream, IL
Vehicle:
'01 GC8 Dinged STM
'09 Concours 14 ABS Black

Default

you CAN NOT over adjust the valves...you WILL burn an exhaust valve because it is not using the valve seat as a heat sink properly...set them to .25mm on the exhaust and .20mm on the intakes...any tighter and you risk burnign a valve.

jeremy
HndaTch627 is offline   Reply With Quote
Old 07-09-2002, 02:28 AM   #6
HndaTch627
Scooby Guru
 
Member#: 6551
Join Date: May 2001
Chapter/Region: MWSOC
Location: Carol Stream, IL
Vehicle:
'01 GC8 Dinged STM
'09 Concours 14 ABS Black

Default

Quote:
Originally posted by ColinL
you will probably experience excessive cam wear if the lash is less than the minimum factory spec, which is the (IIRC) .008" and .010" listed under the hood and in the FSM.
colin the specs under the hood are wrong...they are not what the manual says to set them at...the ones under the hood are maximum allowable clearance, not the desired clearance
HndaTch627 is offline   Reply With Quote
Old 07-09-2002, 05:43 AM   #7
Corey
Scooby Specialist
 
Member#: 618
Join Date: Dec 1999
Location: PA, USA
Vehicle:
2000 2.5 RS #89 STS
MODERacing / Bridgestone

Default

Pat,

I used .007 on the intake and .009 on the exhaust as recommended by Cobb Tuning.

Thanks for all the insight guys.

Corey #89 SM
Corey is offline   Reply With Quote
Old 07-09-2002, 08:38 AM   #8
subarumantoo
Scooby Specialist
 
Member#: 3257
Join Date: Dec 2000
Location: Houston, TX
Vehicle:
2000 ImprezaRS
Blue Ridge Pearl

Default

HndaTch627 is correct: Not enough valve lash can cause the valves to burn. When the valves get hot, the stems get longer. If there is not enough clearance, the valve will not seat and hot combustion gasses will go around the valve and burn them. Bad idea to try and make power by cheating on the valve lash specs...
subarumantoo is offline   Reply With Quote
Old 07-09-2002, 10:38 AM   #9
ColinL
Scooby Guru
 
Member#: 114
Join Date: Jul 1999
Chapter/Region: MWSOC
Location: Wichita, KS and Whoring, OT
Vehicle:
'03 Evo, Rice White
'01 Erion CBR 929

Default

jeremy you were on such a roll but you failed to notice that your recommendations are exactly .008" and .010" when converted.

also, the service limit on valve lash is much higher than this number. it's so loose your valvetrain would be clattering viciously... (no comments about keif's momz please. )
ColinL is offline   Reply With Quote
Old 07-09-2002, 01:58 PM   #10
HndaTch627
Scooby Guru
 
Member#: 6551
Join Date: May 2001
Chapter/Region: MWSOC
Location: Carol Stream, IL
Vehicle:
'01 GC8 Dinged STM
'09 Concours 14 ABS Black

Default

Quote:
Originally posted by ColinL
jeremy you were on such a roll but you failed to notice that your recommendations are exactly .008" and .010" when converted.

also, the service limit on valve lash is much higher than this number. it's so loose your valvetrain would be clattering viciously... (no comments about keif's momz please. )
oh it wasn't those numbers colin, it's just that under the hood of the car the allowable clearance is .25mm on the intake and .30mm on the exahust and IIRC the manual had those as maximum allowable clearnances. but i could be wrong, i knew your numbers were right on cause well let's face it, your a damn genious .

Jeremy

p.s.: you said keif's momz sounds like a diesel truck cause she's too loose
HndaTch627 is offline   Reply With Quote
Old 07-09-2002, 09:19 PM   #11
Patrick Olsen
NASIOC Supporter
 
Member#: 120
Join Date: Jul 1999
Chapter/Region: AKIC
Location: Where the Navy sends me...
Vehicle:
1997 Legacy 2.5GT
QuickSilver Metallic

Default

Thanks, Corey, I called Cobb today to confirm and the specs are the same for the DOHC setup.

Pat
Patrick Olsen 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
Deals to be had, money to be saved! GS/GMS/SPT/Walbro subaruwrxparts.com Engine/Power/Exhaust 0 06-19-2009 10:54 AM
Agency Power Wheels in stock!! great deals to be had on enkei's as well! IMPORTIMAGE Wheels/Tires 504 09-16-2008 04:12 PM
how much more power is to be had with an ewg? godforbid67 Newbies & FAQs 1 10-08-2007 02:05 AM
HP to be had with porting? valve seals? deluxsti Factory 2.5L Turbo Powertrain 5 09-09-2005 06:48 PM
Do caps with LCD readouts & remote power on still have to be charged with a resistor? AcquaCow Car Audio, Video & Security 6 04-01-2004 01:49 PM


All times are GMT -4. The time now is 12:05 AM.


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.