What's In a Valve Job...Dart 355CNC R&D
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What's In a Valve Job...Dart 355CNC R&D

  1. #1
    steelcomp was here
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    Default What's In a Valve Job...Dart 355CNC R&D

    I had a customer send me a pair of virtually stock Dart 355CNC heads that we both agreed are too big for his combination, but he wanted to see if there was something I could do to make them better, without making them bigger.
    These heads are already really good from Dart. This pair had been run on a fairly well buit 548 with some compression and cam, and a stock Edelbrock Victor "Reher Morrison" intake (pictured in the intake show and tell thread), but they were basically as delivered from dart (except that someone had "attempted" to port match them to the intake). Fortunately what they did was of no consequence for all intents and purposes.
    The engine combination did tell me one thing for sure...the heads needed more valve area, so the plan was to install a Ferrea 2.35 valve, (heads come with a 2.30) new valve job, mill the heads .030" for more compression, and see how good we can make them without touching the ports. Alst ot note, the cam will be in the ,800" lift range, so I want all the flow I can get below that number, primarily in the .4 - .7 range, or what I call the "threshold" lift area. Above .800 is not as important, so I'm staying with a 45* valve job. A 50-55* valve job would get much better high lift flow numbers, but usually at a trade off for the lower lift numbers on conventional BB Chev heads. That's not something worth trading in this instance.

    First thing to do was get a baseline:
    right/left port

    .2 154.2 / 157.4
    .3 223.2 / 227.5
    .4 292.7 / 287.7
    .5 337.8 / 332.0
    .6 375.5 / 363.4
    .7 401.5 / 384.8
    .8 409.1 / 398.7
    .9 417.1 / 410.8
    1 425.0 / 419.9

    You can see, they're not too shabby out of the box. After this, I did a clean up and blending of all the CNC transitions arounf the valve guide and short turn, and blended the valve job and bowl. There were a couple cfm improvement, but nothing to write home about. It actually lost a few in the lower lift range.

    Next was to install the 2.35 valve with a valve job I like to use. This was the result;

    .2 154.3 / 154.3
    .3 218.5 / 220.3
    .4 284.6 / 287.5
    .5 339.3 / 333.0
    .6 382.8 / 356.6
    .7 401.4 / 382.6
    .8 411.8 / 399.6
    .9 418.8 / 410.0
    1 422.5 / 416.7

    Shows a loss. There's obviously some work to do to justify the change. After several angle changes to the bottom angles on the valve job, back cut changes to the valve and some blending, I was able to recover most of the flow and then some. Eight changes over all, each tested individually to doccument the effect of each change. Making more than one change at a time on something like this can really lead to confusion, especially if the results are negative.

    The recovery;

    .2 157.7 / 158.4
    .3 227.2 / 225.5
    .4 294.4 / 292.8
    .5 347.0 / 333.5
    .6 383.9 / 360.1
    .7 400.4 / 385.0
    .8 415.5 / 404.1
    .9 424.1 / 415.6
    1 430.6 / 421.2

    You can see the gains were significant from doing nothing mroe than playing with the valve job.
    Last edited by scott foxwell; 08-16-2012 at 12:25 PM.
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  3. #2
    gn7
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    CFM gains don't come easy on a already decent set of heads do they?

    Starts getting like finding HP in a Cup engine where 3 HP is a ass whoopin



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    Senior Member carreradude's Avatar
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    Quote Originally Posted by steelcomp View Post
    I had a customer send me a pair of virtually stock Dart 355CNC heads that we both agreed are too big for his combination, but he wanted to see if there was something I could do to make them better, without making them bigger.
    These heads are already really good from Dart. This pair had been run on a fairly well buit 548 with some compression and cam, and a stock Edelbrock Victor "Reher Morrison" intake (pictured in the intake show and tell thread), but they were basically as delivered from dart (except that someone had "attempted" to port match them to the intake). Fortunately what they did was of no consequence for all intents and purposes.
    The engine combination did tell me one thing for sure...the heads needed more valve area, so the plan was to install a Ferrea 2.35 valve, (heads come with a 2.30) new valve job, mill the heads .030" for more compression, and see how good we can make them without touching the ports. Alst ot note, the cam will be in the ,800" lift range, so I want all the flow I can get below that number, primarily in the .4 - .7 range, or what I call the "threshold" lift area. Above .800 is not as important, so I'm staying with a 45* valve job. A 50-55* valve job would get much better high lift flow numbers, but usually at a trade off for the lower lift numbers on conventional BB Chev heads. That's not something worth trading in this instance.

    First thing to do was get a baseline:
    right/left port

    .2 154.2 / 157.4
    .3 223.2 / 227.5
    .4 292.7 / 287.7
    .5 337.8 / 332.0
    .6 375.5 / 363.4
    .7 401.5 / 384.8
    .8 409.1 / 398.7
    .9 417.1 / 410.8
    1 425.0 / 419.9

    You can see, they're not too shabby out of the box. After this, I did a clean up and blending of all the CNC transitions arounf the valve guide and short turn, and blended the valve job and bowl. There were a couple cfm improvement, but nothing to write home about. It actually lost a few in the lower lift range.

    Next was to install the 2.35 valve with a valve job I like to use. This was the result;

    .2 154.3 / 154.3
    .3 218.5 / 220.3
    .4 284.6 / 287.5
    .5 339.3 / 333.0
    .6 382.8 / 356.6
    .7 401.4 / 382.6
    .8 411.8 / 399.6
    .9 418.8 / 410.0
    1 422.5 / 416.7

    Obviously some work to do to justify the change. After several angle changes to the bottom angles on the valve job, back cut changes to the valve and some blending, I was able to recover most of the flow and then some. Eight changes over all, each tested individually to doccument the effect of each change. making more change than one on something like this can really lead to confusion, especially if the results are negative.

    The recovery;

    .2 157.7 / 158.4
    .3 227.2 / 225.5
    .4 294.4 / 292.8
    .5 347.0 / 333.5
    .6 383.9 / 360.1
    .7 400.4 / 385.0
    .8 415.5 / 404.1
    .9 424.1 / 415.6
    1 430.6 / 421.2

    You can see the gains from doing nothing mroe than playiong with the nvalve job were significant.


    Now in just doing the work you did, what kinda gains in power would be had? Is it worth the time and effort?? (Honest question)

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    steelcomp was here
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    On to the next step...mill the heads .030. I know where this is going to take me...right in the trash...


    After milling .030"; (right port only, just looking for a trend) #1 right port;

    .2 154.0
    .3 220.9
    .4 286.8
    .5 338.0
    .6 371.5
    .7 391.5
    .8 404.8

    LOL...no need to go any further than that.

    Same thing, only this time I went to a different valve all togehter with a different top angle and a completely different approach. After 5 differetn cchanges, I was able to recover again. Remember, this is all strictly valve job...I haven't touched the ports.
    At one point, a simple 2* change in the valve back-cut angle netted a 13cfm gain.


    The right port finally cama around after a dozen changes or so...again, each being tested on the flow bench individually and doccumented.

    Final flow on the #1 right port;

    .2 161.2
    .3 229.7
    .4 298.0
    .5 353.4
    .6 391.9
    .7 407.2
    .8 425.5
    .9 437.1
    1 441.4

    The left port proved to be more of a challenge. After the recovery from milling, I could see the mid flow numbers had really suffered, and the split between teh right port and left port was just too high.

    #7 left port after recovery;

    .2 160.8
    .3 228.0
    .4 297.0
    .5 330.4
    .6 355.5
    .7 379.2
    .8 396.9

    Again. no need to go any further. I need to fix this.
    Last edited by scott foxwell; 08-15-2012 at 09:47 PM.
    If God is your co-pilot, change seats!
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    After talking with a few "leading people" in the industry, I decided to try a completely different valve job for the left port, moving away from my "favorite", which was working really well in the right port.

    First test, new valve job, #7 left port;

    .2 153.0
    .3 223.1
    .4 288.4
    .5 332.1
    .6 358.5
    .7 377.8
    .8 399.5

    Well damn...that didn't work.

    OK...back to my own "formulas", but also keeping the foundation of this new valve job...just a few subtle "adjustments".

    Final flow, #7 left port;

    .2 156.9
    .3 225.4
    .4 294.8
    .5 340.9
    .6 370.0
    .7 387.3
    .8 413.4
    .9 431.4
    1 438.8

    There is probably a thousand million zillion different possible valve job combinations so at some point you have to declare a victory, but I think this is a pretty good illustration of just what can...and can be accomplished. It's an eye opener considering nothing else was changed.
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    Quote Originally Posted by carreradude View Post
    Now in just doing the work you did, what kinda gains in power would be had? Is it worth the time and effort?? (Honest question)
    Some of the power gain will be from improving the velocity profile with the larger valve. More area and still keeping the airspeed through the valve in a good range will make more power. How much more will depend on a lot of factors. By virtue of the airflow increase alone, you can figure 2.4-2.5 hp/cfm potential on a build like this. The other part of this is the cam. With this kind of information (I have flow numbers for all 8 intake and exhaust ports) the cam designer can get much closer to optimal with his design. Combine this work with the manifold, a better cam, and a slight increase in compression, there could easily be 100hp on the table.
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    Quote Originally Posted by gn7 View Post
    CFM gains don't come easy on a already decent set of heads do they?

    Starts getting like finding HP in a Cup engine where 3 HP is a ass whoopin
    This "test" took close to 60 hours and probably 40 different changes which means 40 different trips from the seat and guide machine to the flow bench, and back and forth. I have 6 pages of flow numbers. I think in the end, it was a worthwhile endeavor, and NO, the customer will not pay for all those hours. Most of this was on me.
    Last edited by scott foxwell; 08-15-2012 at 10:12 PM.
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    Some pics;











    Pretty good line of sight. A lot can be learned from these two pics:





    ex port needed very little work:



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    gn7
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    Quote Originally Posted by steelcomp View Post
    This "test" took close to 60 hours and probably 40 different changes which means 40 different trips from the seat and guide machine to the flow bench, and back and forth. I have 6 pages of flow numbers. I think in the end, it was a worthwhile endeavor, and NO, the customer will not pay for all those hours. Most of this was on me.
    Whew, thank goodness. I thought that hissing sound I heard was the money leaving my wallet for my next valve job!
    Hopefully you are not one of those types that speads the R&D costs across ALL your customers?



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    Quote Originally Posted by gn7 View Post
    Whew, thank goodness. I thought that hissing sound I heard was the money leaving my wallet for my next valve job!
    Hopefully you are not one of those types that speads the R&D costs across ALL your customers?
    No, just the ones who give me the most grief.
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    Quote Originally Posted by steelcomp View Post
    No, just the ones who give me the most grief.
    I CAUSED YOU NO GRIEF........you loved the challenge....
    Formally know as UNFORGIVEN...

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    gn7
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    You know me Scott, grief is how my last name is mispronounced.

    This is an excellent thread becasue it shows the little things that can make a big difference in how much power the thing makes and where the power is. You could have met or exceeded the flow numbers with a bigger head, bit it doen't mean it wuld have the same power under the curve. And "under the curve" is much bigger than most know, or will admit to.

    Good job.



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    Once again is WHY UR THE BEST AT WHAT YOU DO !!!!!!! Not bad for a damd ol carpenter
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  16. #14
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    Quote Originally Posted by TNYoungblood View Post
    Once again is WHY UR THE BEST AT WHAT YOU DO !!!!!!! Not bad for a damd ol carpenter
    I thought it was an ol dry waller that dapples in carpentry.



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