Gt40 heads, On My mav, question.

Discussion in 'Technical' started by 464925, Dec 26, 2020.

  1. 464925

    464925 Maverick 1973-Pure Muscle

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    Hello.
    I bought a set of gt40 heads.
    Wanna Buy that cam.
    It's a 73 302. Daily driver.
    Do i need to chance the valve springs? Hope not but i'm case this works? COMP Cams 942-16
    Thanks for advice.


    Grind Number:XE262H
    Engine Family:Ford 221, 260, 289, 302 c.i. 8 Cylinder (1963-1995)
    RPM Operating Range:1,300-5,600
    Cam Type:Hydraulic Flat Tappet
    Lifter Style:Hydraulic Flat Tappet
    Camshaft Series:Xtreme Energy
    Camshaft Gear Attachment:1-Bolt
    Usage:Street/Performance
    Valve Springs Required:Yes
    Camshaft Material:Cast Iron
    California Proposition 65:WARNING: Cancer and Reproductive Harm P65Warnings.ca.gov
    Advertised Intake Duration:262
    Advertised Exhaust Duration:270
    Intake Duration at .050 Inch Lift:218
    Exhaust Duration at .050 Inch Lift:224
    Intake Valve Lift:0.493
    Exhaust Valve Lift:0.5
    Lobe Separation:110
    Assembly Lubricant Included:Yes
    Intake Centerline:106
    Lobe Lift Intake:0.309
    Lobe Lift Exhaust:0.313
     
  2. Mustang1989

    Mustang1989 Member

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    I’d definitely opt for a good set of springs if the gt40 heads don’t have the dampeners in the springs. What you’re gonna want to get that you may not have thought of is a mild stall torque converter if you’re running an automatic transmission. With the 110 degree lobe separation she’s gonna have a rough idle. Another thing about the gt40 heads is that they require the use of a unique exhaust header. If I remember correctly they are pretty expensive.
     
  3. Krazy Comet

    Krazy Comet Tom Supporting Member

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    Agreed on cam..

    GT40 heads use std headers, GT40P require special headers.
     
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  4. Mustang1989

    Mustang1989 Member

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    Thanks for the correction on the heads KC! It’s been a while and I’d forgotten about the “P” heads being the ones needing the special headers.
     
  5. Ivan Colesnic

    Ivan Colesnic Member

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  6. BBMS18

    BBMS18 Member

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    +1
    These are what I’m looking at for the 5.0 going in my Comet, everything you’ll need in one kit(y)
     
  7. greasemonkey

    greasemonkey Burnin corn

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    Get a set of drop in beehive springs.
    https://www.alexsparts.com/
    And I'd go one size bigger on the cam. Maybe even retrofit a roller.
     
  8. 464925

    464925 Maverick 1973-Pure Muscle

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    Thanks for reply. :cheers2:My car is my daily driver, 4 barrel edelbrock 600cfm, performer intake 289. electronic ignition, top loader 4 speeds.

    Think that cam was ok. Can u suggest one?
    My first options was.

    https://www.compcams.com/xtreme-energy-212-218-hydraulic-flat-cam-for-ford-221-302.html


    Grind Number: XE256H
    Engine Family: Ford 221, 260, 289, 302 c.i. 8 Cylinder (1963-1995)
    RPM Operating Range: 1,000-5,200
    Cam Type: Hydraulic Flat Tappet
    Lifter Style: Hydraulic Flat Tappet
    Camshaft Series: Xtreme Energy
    Camshaft Gear Attachment: 1-Bolt
    Usage: Street/Performance
    Valve Springs Required: Yes
    Camshaft Material: Cast Iron
    Advertised Intake Duration: 256
    Advertised Exhaust Duration: 268
    Intake Duration at .050 Inch Lift: 212
    Exhaust Duration at .050 Inch Lift: 218
    Intake Valve Lift: 0.477
    Exhaust Valve Lift: 0.484
    Lobe Separation: 110
    Assembly Lubricant Included: Yes
    Intake Centerline: 106
    Lobe Lift Intake: 0.299
    Lobe Lift Exhaust: 0.303

    But the lobe is the same.

    Isn't that kit too much?

    stock gt40 springs don't work, right?

    these were my first choice. They are not good?

    https://www.compcams.com/single-outer-valve-springs-1-437-o-d-1-039-i-d-1.html
     
  9. 464925

    464925 Maverick 1973-Pure Muscle

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    Lobe separation 110. Is like stock cam. Why rough idle?
     
  10. Mustang1989

    Mustang1989 Member

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    Most stock cams are in the 114 to 116 degree range. In this case the stock 5.0 cam has an LSA of 115 degrees.

    114 degrees is actually somewhat noticeable while 112 produces a noticeable lope. Starting at 110 you start getting into rough idle . At least that has been my experience .
     
    Last edited: Dec 27, 2020
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  11. stumanchu

    stumanchu Stuart

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    GT40 heads have exhaust valve rotators on all the exhaust valves. If you get the Alex Parts drop in spring kit, you can get rid of the rotators. It requires special valve spring retainers and valve locks for the exhaust valves, which come in the kit. I like the GT40 heads in my combo, and my cam is a stock mustang GT cam. @ .050 211/211, about .450 lift, 116(?) LSA. What gear do you have? The four speed is a big plus. Do you have headers? What kind of mileage do you get, and is that important?
     
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  12. Mustang1989

    Mustang1989 Member

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    The four speed is a big plus. No stall converter needed if going for a little more lope in idle conditions. That XE256H cam sounds pretty good for a daily driver. With 110 degree LSA you're gonna get a good sounding rough idle and with the mods that you've listed the rpm range with a 5200 rpm redline sounds about right. Should make for a good daily driver with good driveability. Stu did bring up a good point with the gears. What ratio do you have back there?
     
  13. Krazy Comet

    Krazy Comet Tom Supporting Member

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    Agreed but we don't know if it's a wide or close ratio. Small blocks with close ratio trans and 2.79/3:00 gears or so are prone to be doggish. A big cam would make matters worse.

    The reason 2.79/3.08 worked so well in 5.0 Stangs, the T-5 used a 3.35 1st gear. First gear cogs in a wide ratio toploader were 2.78 & close ratio are a paltry 2.32. Also didn't hurt that the EFI, HO long runner intake kicked out probably 40ft lbs more torque.

    A little math 3.35 x 3.08 = 10.3 1st gear, while 2.32 x 3.00 only gives a 6.96. The 2.78 1st with 3.00 = 8.34.
     
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  14. Mustang1989

    Mustang1989 Member

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    I've gotta say.....you know your stuff in regards to transmissions/ gears and cam selection. Wondering what the best all around cam would be for a guy that does this kind of stuff recreationally would be though. I ran an F cam in my 5.0 which was perfect for the 4.10 ratio it had but then again.....we're talkin' toploader 4spd here and we still need the gear ratio on the diff to determine what this fella might need.
     
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  15. stumanchu

    stumanchu Stuart

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    In my car, I went with less cam, better iron heads, probably + 1 1/2 more compression, and a dual plane intake that matches everything better. I am learning as I go, but I can say that the biggest problem I have now is traction with an open 3.25. Traction was never an issue with the previous motor, it was a dog for reasons the cam could not compensate for.
     
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