kewlbrz

mabey a dumb question, but what is the bennefit of putting a 2.02 valve in a stock valve seat in an LS1/LS6 or 5.3 head, etc., if the seat size doesnt change, the flow would seem like it would be the same. In fact, it would seem the larger valve would hinder flow, if the seat wasnt enlarged to compliment(maximize) it.

00UNTAMED

Well if you put a larger valve in place were a smaller valve goes u will hurt the flow more than anything. Unless u took your heads in a shop and had the area underneath the valve opened up for the larger valve.

The largest valve that you should go on a street
car should only be 2.02 even if you went to a 2.05 you could gain little or no power. There has be dino runs by SMOKY YUNIC that he gained little or no power from a larger valve.

So I hope I helped out some. If you need more info I'll check this web out later! <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />

The only time you would like to go to a larger valve is when you are operating at higher rpm's.
<img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> or if you are pushing the cubic inches. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> All that I'm talking about is 346ci though. You could benifit more power for larger valves with more ci but then you won't really have the rpm's that you could be looking for. That is if you are looking for high rpm's but remember rpm's do KILL a engine. <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />

kewlbrz

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 00UNTAMED:
<strong>Well if you put a larger valve in place were a smaller valve goes u will hurt the flow more than anything. Unless u took your heads in a shop and had the area underneath the valve opened up for the larger valve.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Hmmmm, to me that still doesnt explain why putting a larger than stock valve in a stock size valve seat can flow better, even if the material behind the seat is removed, it still has to go through the same size opening.

Scalpel

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by kewlbrz:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 00UNTAMED:
<strong>Well if you put a larger valve in place were a smaller valve goes u will hurt the flow more than anything. Unless u took your heads in a shop and had the area underneath the valve opened up for the larger valve.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Hmmmm, to me that still doesnt explain why putting a larger than stock valve in a stock size valve seat can flow better, even if the material behind the seat is removed, it still has to go through the same size opening.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Great point, kewl. Also, opening up the material behind the valve would make the opening larger and thus decrease velocity. I'm with Kewl on this one. I'd love to know the answer.

LOnSLO

iTrader: (15)

If you waste your time opening up the bowl area without porting the runners also, then yes, you will see no additional flow.

kewlbrz

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by LOnSLO:
<strong>If you waste your time opening up the bowl area without porting the runners also, then yes, you will see no additional flow.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Ok, but that still doesnt seem to answer the question as to why a larger valve (2.02) in a stock seat is better somehow. In fact it seems it would hinder flow in a stock seat.

Tin Indian

Well, the stock valve is 2.00"
Then many of these head porters install a 2.02" valve in the stock seat.

I just can't see how a valve that is only [2 thousands] bigger is going to do anything.

2 thousands is almost nothing in my opinion

Oh ya, and then they change out the stock 1.55" exhaust and put in a 1.57"
Of course we get charged alot more for these "Bigger" valves. 2 thousands of an inch is not my idea of "Bigger" (especially in the stock valve seat)
__________________________________________

<small>[ October 17, 2002, 10:33 PM: Message edited by: Kimchee and Rice ]</small>

Red2000SS

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>Well, the stock valve is 2.00"
Then many of these head porters install a 2.02" valve in the stock seat.

I just can't see how a valve that is only [2 thousands] bigger is going to do anything.

2 thousands is almost nothing in my opinion

Oh ya, and then they change out the stock 1.55" exhaust and put in a 1.57"
Of course we get charged alot more for these "Bigger" valves. 2 thousands of an inch is not my idea of "Bigger" (especially in the stock valve seat)
__________________________________________</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It's 2 HUNDREDTHS of an inch, not 2 THOUSANDTHS.

Still doesn't seem like much difference...

Brian Tooley Racing

iTrader: (13)

Well, heres the deal. First off 2.02 is 2 tenths or 20 thousandths bigger, not 2 thousands. The valve and the valve job form a 360 degree radial venturi. Now if you can swallow that the intake bowl to chamber transition is one half of the venturi the other half of the venturi is the back side of the intake valve leading into the chamber, but wait, the other half of this venturi is gone, so generally the thicker you make the valve margin, or the edge of the valve 90 degrees from the face, the more you extend this missing venturi. Now, with that being said the stock valve has a very thin margin, around .020"-.030", the aftermarket valve has about a .080" thick margin. On our CNC ported head a stock intake valve only flows 266-268cfm where the Ferrea aftermarket valve flows 295-305, which is more then the other 2.02 aftermarket valves flow! This thicker margin is what makes a aftermarket valve generally flow more air. If you do not backcut the intake valve (a 30 degree angle behind the 45)it will flow more up top but less mid lift. This is what a lot of porters do to get the big top end flow, we did it too at one time. If you backcut the intake valve it adds alot of mid lift but hurts top end. So what we go for is lots of "area under the curve", I will post a link to a story on this. To give you some idea how the valve munipulates the flow curve I will show approximate flow at .3 and .6 for each different valve with a ported head. At .3 the stock valve is 208cfm, after market 185cfm, after market with a backcut 200 cfm. At .6 stock valve 267, aftermarket 315, aftermarket with a backcut 302. So you can see there are indeed huge differences in flow between valves, but not because of size so much as shape. Brian at TEA 270 782-6397

Brian Tooley Racing

iTrader: (13)

Da, i mean hundredths, not tenths

Tin Indian

sorry...double post

<small>[ October 17, 2002, 11:31 PM: Message edited by: Kimchee and Rice ]</small>

Tin Indian

Brian....

And I meant 2 hundreths of an inch, and not 2 thousands... duh, oh well

Great explanation! Thats why you don't run a flight simulation facility, and I certainly ain't NO head porter! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Ron,

JPR

I have alot to say about this topic, but I will only mention that valve size is only as good/functional as the porter behind the die grinder.

Joe.