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4.0 Whipple pulley size

Discussion in 'SVT Shelby GT500' started by RI GT500, Jul 7, 2019.

  1. RI GT500

    RI GT500 Member Established Member

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    I have a fully built motor with a 15% crank . With my 4.0 Whipple and a 4” blower pulley , I’m wondering what kind of boost it’ll make ?
     
  2. JimIII@jdm

    [email protected] Authorized Vendor Authorized Vendor

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    Same combination we run on Cobra Jet Mustangs they make about 25-26 psi. Factoring they run open headers but sport 10:1 compression. You should be somewhere close to that still. My opinion, it's a TON of boost for pump gas. I would only run that much on race fuel or E85. Otherwise I would get a STOCK size ATI balancer ring and replace your 15% with that until your running better quality fuel.
     
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  3. RI GT500

    RI GT500 Member Established Member

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    Thank you !! I’m going to run E-85 . Maybe a 93/Torco tune as well , I guess I’ll drop the boost for that , thanks again
     
  4. lexustech48

    lexustech48 RIP FoMoCo 1903-2014 Premium Member Established Member

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    Is 4" pulley the largest Whipple makes for the 4.0L? Im thinking bout running that blower with a stock size balancer like @[email protected] recommended. I want to run 9.5 or 10:1, but Im going to add cams. Likely on Flexfuel for street hooning then race fuel/race e85 for the track or grudge nights in Mexico.
     
  5. RI GT500

    RI GT500 Member Established Member

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    Exactly
     
  6. gtmustang00

    gtmustang00 Active Member Established Member

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    Did you ever do a 93/torco tune? What did it make for power? My buddy has a stock 5.8 with a 4.0 Whipple and he's having some issues with it. Trying to figure out what it should make roughly on 22 lbs.
     
  7. genesmob

    genesmob Active Member Established Member

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    I have a jdm 1500 long block with ss cams (love it) With a 15pct lower and a 4” upper it makes around 19-20psi in warm weather, Iat2 stays very cool with a triple pass he and a 14’he pump. With a 3.75 pulley it’s 21-22psi and around 1000whp (auto loses over 50whp compared to stick) with 16.5 deg on pump e85. Under [email protected] in the quarter in a full wt convertible so far. I’ve dynoed with smaller pulleys and the 4.0 isn’t done yet.


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  8. lexustech48

    lexustech48 RIP FoMoCo 1903-2014 Premium Member Established Member

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    What compression pistons are you running?

    How much extra boost do you estimate that 15% balancer adds to the 4.0 upper?

    I've got my eye on a 4.0 whipple in the future, but want to run on pump gas for road trips, cruising and such.
     
  9. genesmob

    genesmob Active Member Established Member

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    Compression is around 9.8:1.
    15pct lower is the only balancer I’ve had. I run the 4” upper on 93 octane for a couple tanks before I put it away for winter but I don’t beat on it and under 12 deg. of timing.


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  10. lexustech48

    lexustech48 RIP FoMoCo 1903-2014 Premium Member Established Member

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    Thats good to hear, Im considering 10:1 for my pistons. Id be doing the same with timing, but with less boost on a stock balancer it should be a smidge safer for my goals.

    I appreciate the reply!
     

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