4.5 Whipple

[In426WeTrust]

I'm really considering upgrading to the 3.8 whipple from my 4.5 whipple. But before I do I want to pulley down. Has anyone in here run or ran a 4.5 whipple & what was the smallest pulley you ran. I'm thinking of dropping down to a 4.25. If anyone ran a 4.25 upper what was your experience

 

[Unholy707]

I had a 5 and 4.75. Made 900 whp on the 5 with conservative tune. Don’t switch to the 3.8 if your 4.5 has been problem free.

 

[Marc W]

I ran a 4.0 with the +10 at the crank. Made 1202 at the wheels thru a T400 and a 9” rear. That’s close to 1300whp with the factory trans and rear. Secrets to getting the 4.5 to work…. Plenum spacer is a must. One of the billet tensioners to keep the belt on, and an ice box or interchiller to keep it cool.

 

[In426WeTrust]

I ran a 4.0 with the +10 at the crank. Made 1202 at the wheels thru a T400 and a 9” rear. That’s close to 1300whp with the factory trans and rear. Secrets to getting the 4.5 to work…. Plenum spacer is a must. One of the billet tensioners to keep the belt on, and an ice box or interchiller to keep it cool.

1300

I ran a 4.0 with the +10 at the crank. Made 1202 at the wheels thru a T400 and a 9” rear. That’s close to 1300whp with the factory trans and rear. Secrets to getting the 4.5 to work…. Plenum spacer is a must. One of the billet tensioners to keep the belt on, and an ice box or interchiller to keep it cool.

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T400 13000 rwhp. That just sounds like a Beast! - I'm getting my car dyno tuned for the first time in a week & my goal is to reach 1000RWHP. I don't know if my current pulley combo 5" upper 10% lower ati , E85 - dual pumps & long tube headers will make that . So I was thinking of just dropping down to a 4.5 or maybe even 4.25 come dyno day. but also knowing I'm stock bottom end right now & don't want to get too crazy lol.

 

[Marc W]

My engine was a built 426 so those numbers reflect that. As far as making the 4.5 work though, those things are what it needs. They are actually a very capable supercharger but with the new gen Whipples established now, they have been left behind. I ran 8.70’s at full 4500 lb weight with that supercharger so they have a lot more capability then they are given credit for.