Selecting Cylinder Heads

Discussion in 'Engine Topic' started by Riley, Mar 13, 2021.

  1. G72Zed

    G72Zed Veteran Member

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    Lowend makes some key points above, and to support his points, I just got back from the dyno testing/tuning one of my custom built carbs/spacers for a GM 350 crate 602 with the L31 Iron Vortec heads. This engine uses the same L31/heads as GM's 350 HO 330HP street crate engine.

    Weather they are Vortec 906 or 062, they work amazingly well, I did not go through the "Vortec head guide" as I base all my experience by what I work on, build and tune...so, direct feedback, like today.

    This engine is rated by GM @ 350 HP @ 5,400 and 396 TQ @ 3,800. It comes with 9.12 CR, Hyd FT cam with only .435/.460 lift with 212/222 @ .050 on a 112.5 LSA, all with stamped 1.5 rockers, we did not even take off the valve covers to adjust the valves, out of the "crate" , on the dyno, 2 quick FT/ring break in sessions for 20 minutes and let her fly.....

    Take a look at this dyno sheet, like Lowend states, making power with a basic 350 with Iron Vortec's is a walk in the park. No need for "high lift" cam, the Vortec head flows 230 CFM @ .435 lift, and a 350 cubic inch with that cfm will have a HP peak occurring around 5,400-5,500 rpm, just what GM states, and it hangs on not bad.

    The OEM's know more about CFM/runner shape/port speed/velocities/fill rate/VE/swirl/burn than most cheap over advertised/overseas copies, plus 100 other factors that most don't give the OEM's credit for.

    Now, if I was allowed to "modify" this engine, these heads could support 490hp, but that's a different story.

    And for my own shameless carb plug, note the AFR's and "fuel curves".....it's not much of a curve though.

    Inked350 L31 Vortec Dyno testing_LI.jpg Inked 602 94 octane 2_LI.jpg
     
    Last edited: Mar 16, 2021
  2. 1980RS

    1980RS Veteran Member

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    Too bad they did not put that cam on a 106° LCA that would have helped coming out of the corners with that engine. With nothing more than a bowl port, slimmed guides and a little epoxy in a certain spot with a 1.94 valve I managed to get more than 250cfm on the intake side and almost 190 exhaust with a 1.5 valve. Crazy numbers for not a lot of work. Looks like you have a nice dyno there G72.
     
  3. carhead22000

    carhead22000 oldblue

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    get hold of dan at d.w.a performance...he will get you heads and work them for you.very smart engine shop.
     
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  4. grumpyoldrat

    grumpyoldrat New Member

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    With your engine set up,
    I factory heads would be ideal. I would look at buying a set of 882 heads. They can be massaged for more performance, won't break the bank and work with unleaded gas.
     
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  5. dickeymoore

    dickeymoore Veteran Member

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    Look at the Promaxx heads great heads for the $$$$
     
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  6. CT1275

    CT1275 Member

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    One thing you really want to look for, after the casting numbers, are cracks. The stock Vortecs are a thinner deck and known to crack. There are good ones out there but cracks are possible. If those casting numbers are not what someone has, dont let them convince you they're Vortec because of center bolts. TPI heads are center bolt and they flow bad and have bad chambers (not Vortec!)
    You can also look after market. I've heard some GMPP Vortecs are under $1000. Other companies make these castings as well with extra material that can be surfaced and wont crack as easy. I bought Vortec castings with the correct cast # from Promaxx for about $860 for a complete built pair, good to .575 lift, screw in studs, 2.02/1.60 valves, 64cc chamber, 183cc intake port. Good flow. I think their flow numbers are advertised a little low. Mine flowed really good on the bench, but I did do a little porting. They flow pretty good with no porting though.
    I'm considering eventually going to aluminum and if I do will probably go with Blue Print Engines. Budget aluminum head that I've heard is good. Closer to $1000 though.
     
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  7. G72Zed

    G72Zed Veteran Member

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    This is a "sealed" DIRT spec rule class, so no changing that!!. Almost the same cam in the other GM "crate" offerings, so idle quality, tuning window, wider flat curves instead of a more peaky curve and a narrower power band is what they are after. With such low lift and small duration the LSA is somewhat balanced, and keeps the cylinder pressures in check as well. As the head get's better and more balanced, the wider the LSA can be used, everything being equal.

    Yes, those Vortec's can make power out of mid lift cams and some work like you do, 250 CFM can support 515 HP in a well built pump gas SBC.

    It's my buddies dyno, not mine, but I'm on it all the time anyway.
     
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  8. Z-Life

    Z-Life Nasty Member

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    Gone are the days when you could go to the salvage yard and find some double hump sbc heads just laying around, or on a wrecked car. 2.02 1.90s and depending on the condition you could get by with new springs, guides and a valve job. Hot rodding has changed so much so many choices and combinations. I dont think you can go wrong with some aluminum edlebrock performers @700-800 price range. Hopefully you'll have some money left over for an intake and cam, there is where you need to take some time deciding, I would say to first determine what you want as the end result and do what it takes to get there. Not a daily I'd go crazy but make plans for no vacuum at the intake, you will then be doing manual brakes, electric booster, or hydro boost brakes. So its a never ending process of spending money..... the guy next to you at the light has 15" rotors and 18" rims with an ls3 in his 2nd gen. as far as 119k a lot of miles on vortecs, well yes and no, vortecs can be good for 2-300 thousand miles, but if your going to put in a crazy cam better get some better springs.
     
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  9. need-for-speed

    need-for-speed Veteran Member

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    Why do you want to remove the 700R4? When I replaced my Turbo 350 with a 700R4, I could not believe what a difference the lower first gear made. I can burn rubber from here to Dallas LOL. You will miss that lower first gear.
     
  10. 1980RS

    1980RS Veteran Member

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    After you run a set of Vortec's stock with a good valve job one will never use a double hump head again, I know I don't. My last sew was some home ported 186's that I thought were pretty good, dropped on a set of mild ported 292 Turbo heads and the car went from 12.6 to 11.9, after that I put my 1st set of home ported Phase 1 Bowtie heads on and the car was in the 11.6'[email protected] Last year the mild Vortec heads I did blew all of the others away. Made me a believer.
     
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