4.0 Whipple pulley size

RI GT500

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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 ?
 

JimIII@jdm

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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 ?

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.
 

RI GT500

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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
 

RedVenom48

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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
Is 4" pulley the largest Whipple makes for the 4.0L? Im thinking bout running that blower with a stock size balancer like @JimIII@jdm 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.
 

gtmustang00

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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.
 

genesmob

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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 9.2se@152 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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RedVenom48

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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 9.2se@152 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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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.
 

genesmob

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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.


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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RedVenom48

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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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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!
 

ItsReal

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What issues? Reason I ask is I have a stock 5 8 with a 4.0 whipple and a 4" pulley and l&m cams. Just wondering what I should be on the lookout for when it comes to any issues.
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.

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