I asked this question before with no response.
Surely someone know something about this.
I read about this in one of David Vizard's books.
He explains that most valves have a 45 degree face, meaning the valve makes contact or seats on the 45 degree cut (or face) of the valve seat. He goes on to explain that if you were to grind the valve face to 30 degrees so that it makes contact with the 30 degree cut (or face) of the valve
seat, more flow would be availble at low lifts, ie. more HP!
At low valve lifts, a 30 degree valve is further off the valve seat than a 45 degree valve. It is similar to having a recessed (valve sunk low in the seat) valve. At low lifts the valve is shrouded by the seat. A valve that seats on the highest portion of the seat would be unshrouded almost immediately when opening. Anybody following me here? I know my terminology may not be exactly right.
Do any of the LS1 head porters set up valves with 30 degree seats?
Anybody have any info on this.
__________________ Current project - 98' BMW M3 LS1 conversion
09/2008 - Parting out 02' Z28 - misc stuff left
05/2005 - SOLD - 99' NBM T/A, Mac Headers, Hooker Catback, 224/222 .568 112 CC XE cam, CNC heads, Eibach Pros, Bilstein HD's, Spohn Adj. PHB,
SpeedLine Aleisios.
Well, you are asking people to give up trade secrets. I am not sure there are ANY shops that will give up that kind of info. Although most shops just drop in an off the shelf valve. Ours are custom machined in house.
You do see a better flow number at low lifts but it is at the sacrifice of high lift flow. Common valve angles are to seat on the 45 and backcut with a 30. I would be interested in knowing what the big guys are doing. The norm may not apply to these heads as they have a different combustion chamber than the traditional SBC.
what you end up with is an engine that is hard to tune,very camshaft sensitive and has little top end power. (with such strong low numbers they are prone to sucking alot of fuel out of the pipe if not mated with the proper cam.)
His info in his books a few years old.And not what is used by Hi-Po Cylinder head shops.
__________________ 2003 Busa it does have a nice exhaust
30' seats were done on low reving, low cam lift motors years ago from the factory.For instance
most of the old pontiac motors such as the 400 and 455 had 30' seats.
David Vizard will spec you out a cam too for a small fee. <img src="images/icons/smile.gif" border="0"> Check out www.davidvizard.com and take the cam shaft tech break through link.
Go to the bottom of the page for the details.
I would love to know what kind of cam he would spec for a S2 head on a stock cubed LS1. <img src="images/icons/smile.gif" border="0">
But I ain't giving him any money. <img src="images/icons/tongue.gif" border="0">
Wizkid,
Yea, I called that place to get "custom" cam
specs for my SBC 408, worthless in my opinion.
For $30 he the guy gave me ADVERTISED duration and theorectical lift (which was 0.7+ inches).
The advertised duration is worthless since it will vary by manufacturer. He couldn't give me the duration numbers from 0.050 lift to 0.050. He told me obviously I wouldn't want to run 0.7 in. lift, so just pick something in the 0.6+ range. How scientific! Oh yea, you have to give him you credit card number before he runs the program.
If you are building a friggen pro-stock motor or something where money is no object and you can set up a valvetrain for the crazy lift his program suggests, sure go for it.
I just picked a cam after reading about cams that were used in buildups similar to mine. If it doesn't work, I guess I'll be swapping cams.
BTW, I haven't finished my SBC yet. I have been spending too much on the LS1!
__________________ Current project - 98' BMW M3 LS1 conversion
09/2008 - Parting out 02' Z28 - misc stuff left
05/2005 - SOLD - 99' NBM T/A, Mac Headers, Hooker Catback, 224/222 .568 112 CC XE cam, CNC heads, Eibach Pros, Bilstein HD's, Spohn Adj. PHB,
SpeedLine Aleisios.
That sure is disappointing to hear Speed Demon. You don't have his email address do ya?
It sounds like he is ripping the man off. You could have probably made a better pick using DesktopDyno 2000. <img src="images/icons/smile.gif" border="0">
When the time comes, I will see what everyone is doing and go that route. I am glad you reported back to everyone but sorry you got screwed.
Eric
[ November 30, 2001: Message edited by: wizkid ]</p>
?? VALVE face resurfacing 45 deg. or 30 deg.? 
it does have a nice exhaust 
