HP gains from just a valve job?

Discussion in 'High Performance Modifications' started by need-for-speed, Oct 17, 2017.

  1. larrylarry

    larrylarry Veteran Member

    1,292
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    Dec 22, 2011
    San Antonio Tx
    Cylinder heads is where the HP is at. You can gain some HP by doing a valve job but 25 hp is unrealistic IMO. If you’re wanting to do some work yourself you can streamline the valve boss on the intake & exhaust runners. You can grind some off the push rod pinch point but not a lot, contour it some. Gasket matching the intake to the head usually doesn’t help much unless it’s really off but I do it any how. On the intake runners you want to leave a ruff surface like what 60 gr sandpaper roll would leave. Don’t do the exhaust like that only the pushrod boss shaping. A spring change might help to. LS6 springs with the correct retainers, there beehive springs, you can get GM LS6 springs for around 60.00.
     
  2. DB Z28

    DB Z28 Veteran Member

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    Nov 30, 2003
    Fond Du Lac
    Also When doing the 3 angle valve job have them to do a back cut on the intake valve. That helps in the mid range flow
     
  3. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

    .


    Unless you are racing the thing in some heads up class with a head restriction, I would not hog them out another millimeter!!!!
    Porting heads is not something I would trust to youtube.
    Gasket match up 3-4" maybe, but I've seen some brutal hack jobs, and heard even more horror stories!!!
    If you don't know what you're doing, fix what you got and go have fun.

    I would ask about a 5 or 7 angle valve job, and maybe a radius valve job, but honestly even if they found you a touch of HP, is it worth the time, energy & dough??

    Good luck.

    .
     
  4. Bandit723

    Bandit723 Veteran Member

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    262
    Oct 1, 2016
    Waupaca WI
    I would say if your heads are tanked just have them rebuilt and enjoy the car again. If you are looking to gain HP a better set of heads are worth looking at.
     
  5. DB Z28

    DB Z28 Veteran Member

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    Nov 30, 2003
    Fond Du Lac
    Most of your gains will comes from fixing the short turn and bowl work and a good valve job
     
  6. camaro71/holland

    camaro71/holland Veteran Member

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    Aug 27, 2003
    The Netherlands
    Up to ~ 0.150 lift, the most restricting part of the head is the throat and the valve.

    By improving this (first) you gain most for normal (street) driving where the engine benefits from the lower valve openings opposed to max lift for racing.
     
  7. need-for-speed

    need-for-speed Veteran Member

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    Feb 7, 2003
    Conroe, TX
    mrdragster and bandit, I am going to take your advice and just get a regular valve job and not try anything myself.

    $280 valve job includes slight milling, 3 angle, and I'm going to supply new springs from comp cams.

    thanks for the info.
     
  8. 1980RS

    1980RS Veteran Member

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    Jun 17, 2006
    Here is some things I have learned about cyl. heads. Get the best valve job you can afford period, Why? because that is where there are some big gains in HP. I know of one person who was running 12.20's with his old Mopar 440 and was bummed about how slow the car was after getting a valve job by the local machinist. On a suggestion he was directed to a guy who only does performance heads and he paid this guy to redo the other guys work and you know what happened? the 440 now ran 11.70's and that's all he did. I bought my own Sioux seat and valve grinder in 2000, the machine sat until I decided I did not want to pay people for valve jobs any more. I did free valve jobs for people and told them they were Ginny pigs going in on this and if the valve jobs did not work out, well it was free so no bitchin' about it. After that I got pretty good the second year and I did find out something very interesting grinding valves, almost all the new valves I go to cut for people were not concentric and almost everyone of them needed to be trued up on the stones. When I ported and did my first 3 angle valve job on a pair of Bow Tie heads I tossed them on the car and picked up a ton taking the car from the 12.0 range to the 11.70's no other changes. I have read that some heads benefit form a 55° seat but I would need to test the head on the flow bench to see if it works. Since 2012 I have done my own heads and the car keeps going quicker and faster, the heads I have done lately for others say their cars run smoother than they did prior to the work. Cutting seats and valves is a lot of fun IMO and it really lets you see the best performance gains. Oh just so you guys know a good friend of mine who is an NHRA class racer says some of the valve jobs here in MN are in the $1000 range for those cars, ouch.
     
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  9. DB Z28

    DB Z28 Veteran Member

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    Nov 30, 2003
    Fond Du Lac
    The 55 deg seat do flow better and their is a gain but don,t last as long as a 45 deg seat for street use. On the Pro stock heads we use 55 deg seats and we cut the seat profiles with a Newen CNC machine.
     
  10. need-for-speed

    need-for-speed Veteran Member

    620
    1
    Feb 7, 2003
    Conroe, TX
    DBZ28 and 1980 RS , thanks for the good info !
     

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