Legion

I always hear engine gurus talk about how "most" of an engine's power is made at the valves, and a good valve job will make or break a performance engine, etc.

Does any of this pertain to FI motors? I ask because I'm too cheap to pay for fresh valve jobs whenever I disassemble my motor, so I always resort to simply lapping them in. I might possibly consider a performance valve job this time around, but I'm not convinced that the valve/seat angles effect much of anything when I'm cramming in 15psi of air.





Modified by Legion at 1:57 AM 8/11/2007

Civicman86

The more a motor flows the better performance you get. A good valve job will increase the cfm that the head will flow.

quicksilver1689

its all about flow

Legion

Does anyone have any real world, conclusive proof that it's worth it? I'm not talking about flow bench numbers or rambling articles from Endyn on fluid dynamics. I mean has anyone with a turbo motor had it dyno'd, then had a performance valve job done, then had it re-dyno'd to show the difference?

urbansi

To me doing a valve job was always part of a motor build, it gives you a change to inspect your rockers and springs and all that garbage as well as checking valve seats for any abnormalities. I have had my valve done 2 times as well as the seats, its only like $150 and its a nice precautionary measure for the worried driver such as me...

Plus there is nothing worse than when you blow a motor and put it back together to realize that a valve might have slightly bent or floated and then your fresh motor smokes

Legion

Well the valves seat perfectly when I lap them. I pressure test each one to make sure they don't leak. I always fully disassemble, clean, and inspect the entire cylinder head and valvetrain whenever I pull the head off.

I'm wondering about the benefits strictly from a performance standpoint.

tony413

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Legion &raquo;</TD></TR><TR><TD CLASS="quote">Does anyone have any real world, conclusive proof that it's worth it? I'm not talking about flow bench numbers or rambling articles from Endyn on fluid dynamics. I mean has anyone with a turbo motor had it dyno'd, then had a performance valve job done, then had it re-dyno'd to show the difference?</TD></TR></TABLE>

if you dont believe people the people who listed that actually have cars probably much faster than yours why ask this question ? and ALL motors deal with fluid and thermal dynamics if you cant deal with that FACT then have someone else build your motor and be happy.

next you probably wont get a diffinate answer because NO -ONE only gets there valves done only an then go dyno it takes a complete supporting P-N-P to get good results. an if you dont want a valve job because you want to save money then dont do it

agrn93ls

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Legion &raquo;</TD></TR><TR><TD CLASS="quote">Well the valves seat perfectly when I lap them. I pressure test each one to make sure they don't leak. I always fully disassemble, clean, and inspect the entire cylinder head and valvetrain whenever I pull the head off.

I'm wondering about the benefits strictly from a performance standpoint.</TD></TR></TABLE>

Legion...

im with your thinking. a lap in for FI should be sufficient in my opinion. when all motor every little detail is very important with flow but i think some forget to realize that gaining flow on motor versus FI is a bit different. being as that the air is being pressurized/forced into the cyl would theoretically make you wanna think its not important i have nothing to back that up though but in my opinion grinded down guides and multi angles dont apply as much to FI since the pressure forces the air past that. i would think the gains would be insignifficant considering that.

njn63

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by agrn93ls &raquo;</TD></TR><TR><TD CLASS="quote">

Legion...

im with your thinking. a lap in for FI should be sufficient in my opinion. when all motor every little detail is very important with flow but i think some forget to realize that gaining flow on motor versus FI is a bit different. being as that the air is being pressurized/forced into the cyl would theoretically make you wanna think its not important i have nothing to back that up though but in my opinion grinded down guides and multi angles dont apply as much to FI since the pressure forces the air past that. i would think the gains would be insignifficant considering that.</TD></TR></TABLE>

Another way to think about it but on the same track. With an NA motor you're trying to extract every single HP and a "big gain" can be 2-3hp. With a FI application, almost no one is going all out and you can gain 20hp just by upping the boost.

For this reason i'd say if you feel confident lapping the valves in yourself and everything checks out, your money can definitely be put in better places.

Legion

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony413 &raquo;</TD></TR><TR><TD CLASS="quote">the people who listed that actually have cars probably much faster than yours </TD></TR></TABLE>

Oh, is that a fact.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">why ask this question ? </TD></TR></TABLE>

Probably because I was looking for educated responses...? A one sentence response stating "because it flows more" means nothing.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">and ALL motors deal with fluid and thermal dynamics if you cant deal with that FACT then have someone else build your motor and be happy. </TD></TR></TABLE>

Unfortunately, you can't rely on textbook science when discussing engine theory. There are so many different forces acting at once that it would be impossible to predict an outcome based on math and physics. What I'm looking for is a definitive answer in terms of what really matters - overall power output.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">next you probably wont get a diffinate answer because NO -ONE only gets there valves done only an then go dyno </TD></TR></TABLE>

I'm glad you can so confidently speak for the rest of the world. I had no idea you were such an omnipotent being.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">it takes a complete supporting P-N-P to get good results. an if you dont want a valve job because you want to save money then dont do it </TD></TR></TABLE>

I've noticed that you have a penchant for making stupid remarks on this forum. I know I said "all input welcome," but what I meant was "all knowledgeable input welcome."

If I sound grumpy, it's because I wasn't expecting to be patronized for asking an honest question

Legion

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by agrn93ls &raquo;</TD></TR><TR><TD CLASS="quote">
Legion...

im with your thinking. a lap in for FI should be sufficient in my opinion. when all motor every little detail is very important with flow but i think some forget to realize that gaining flow on motor versus FI is a bit different. being as that the air is being pressurized/forced into the cyl would theoretically make you wanna think its not important i have nothing to back that up though but in my opinion grinded down guides and multi angles dont apply as much to FI since the pressure forces the air past that. i would think the gains would be insignifficant considering that.</TD></TR></TABLE>

Well that's what I'm thinking. This particular cylinder head has already been ported out beautifully, it's just lacking a valve job. I can see how portwork would still be beneficial on a forced induction motor (since the smaller ports create a restriction), but I don't get the valve job theory. It's not reducing any restrictions, right? Isn't it just altering the angle of entry for the intake charge? I was under the assumption that multi-angle valve jobs had to do with charging the cylinders, which would be a moot issue on a FI car.

EARLdaSQUIRREL

the valvejob can make or break a ported head, if it makes 3-10hp na, then imagine how much you would gain forced induction.... that would be like saying no need for a better intake manifold because the air is being "crammed" in there..

Legion

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by coptzer &raquo;</TD></TR><TR><TD CLASS="quote">the valvejob can make or break a ported head, if it makes 3-10hp na, then imagine how much you would gain forced induction.... </TD></TR></TABLE>

Well I don't want to "imagine," that's why I'm asking for real data.

DESTROYER

eh, this is the best i can give you:

ka24e single cam motor, forged internals, built for boost. ran 7 months with stock head. 363 RWT.

Same motor, newly ported heads and valves. on a flowbench moved a whopping 68 more cfm than stock. 458 RWTorque. Same tune, same everything.

proof enough for me. unfortunately, i dont have any charts on my comp, so take it or leave it i guess.

tony413

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Legion &raquo;</TD></TR><TR><TD CLASS="quote">

Oh, is that a fact.

Probably because I was looking for educated responses...? A one sentence response stating "because it flows more" means nothing.

Unfortunately, you can't rely on textbook science when discussing engine theory. There are so many different forces acting at once that it would be impossible to predict an outcome based on math and physics. What I'm looking for is a definitive answer in terms of what really matters - overall power output.

I'm glad you can so confidently speak for the rest of the world. I had no idea you were such an omnipotent being.

I've noticed that you have a penchant for making stupid remarks on this forum. I know I said "all input welcome," but what I meant was "all knowledgeable input welcome."

If I sound grumpy, it's because I wasn't expecting to be patronized for asking an honest question </TD></TR></TABLE>

1. your asking a rather unintelligent question ( my opinion)
2. why is it that a Vtec head with the same cam spec on the high side verus a non-Vtec with the same cam specs generally get more HP at lower boost settings ?
3. are you saying that full-race is dumb an shouldnt relie on the thermaldynamic and fluiddymanics studies they did when constructing their manifolds an WG palcement ? also are you calling all the engineers that work at car companies "dumb" because thats how they base some of what will and will not work ?
4. Once some IS proven its usually not a theory anymore
5. i was refering to how you basically called Endyn a dumb im sure he know more about P-n-p then most the people on this forum.
6.EVERYONE on this forum has, have, and will continue to make some bad post hopefully they will learn from it as i have also can you find some of my stupid remarks an PM them to me so i can "set you straight"
7.when was the last time if at any time you seen someone that WAS NOT a company, modify only the valve section of the head and then go dyno ? if they did look to only expect about 1-3hp, as the head is a multi dependent system.
8. sry if i sound like an *** but you didnt have to go there on somethings

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Legion &raquo;</TD></TR><TR><TD CLASS="quote">
Well that's what I'm thinking. This particular cylinder head has already been ported out beautifully, it's just lacking a valve job. I can see how portwork would still be beneficial on a forced induction motor (since the smaller ports create a restriction), but I don't get the valve job theory. It's not reducing any restrictions, right? Isn't it just altering the angle of entry for the intake charge? I was under the assumption that multi-angle valve jobs had to do with charging the cylinders, which would be a moot issue on a FI car.</TD></TR></TABLE>

whats the job of the valves ?
also some of what you just said should give you, your answer
next why is that making valves larger in diameter usually yield better flow ?
the valve itself is a restriction device BUT its there to guide air into the chamber. im assuming that you think just because the cylinder is being "forced" with air that it all goes the same place an doesnt matter. if thats the case why does any run a downpipe or any form of exhaust after the headers or turbo ???

njn63

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Legion &raquo;</TD></TR><TR><TD CLASS="quote">Unfortunately, you can't rely on textbook science when discussing engine theory. There are so many different forces acting at once that it would be impossible to predict an outcome based on math and physics. What I'm looking for is a definitive answer in terms of what really matters - overall power output.
</TD></TR></TABLE>

Yes, yes you can if you're intelligent enough. There is a reason companies have engineers that design stuff on a computer instead of spending days on the dyno. Hell, in the most recent issue of Engine Masters they did a LS2 head shootout and *gasp* the head that flowed the most CFM on the flow bench made the most power.

If you're really interested, there is a 2 page article in the summer issue of Engine Masters about properly sizing valve seats. It sorta pertains to this topic although they didn't do any dyno testing because it's not necessary and gains on a dyno depend so much on setup.

Civicman86

I don't really see why "the motor flowing more air" does not suffice? There is no explanation really needed if you understand how the motor works. Motor = air pump. The more air you get into the motor the more power you will gain. Hence why people add those hairdryer looking things. Why do you think people are so worried about before and after CFM's when getting headwork done?

Also your right you can't really rely on theory but if you understand the theory then you will have your answer. The theory will usually give you an answer that is the absolute best, because like you said there is usually other forces that are not taken into account, usually for simplicity.