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Discussion Starter #1
Just an idea I'm kicking around. Would a custom box upper on a gt40 lower offer any significant gains/losses on a turbo 5.0? If I decided to go with it, it'd be down the road, like a year. What I'm picturing is the upper the length needed to match the gt40 lower, and about 6" x 6", with it sitting directly on the lower. What made me think of of this was looking at my engine since the EDIS conversion. Since there is no distributor in the way now I could run the TB on the front of the box instead of the side. Why? Well, I think there'd be some advantages. I could mod the intercooler and run the charge pipe in a basically straight line. It'd afford me much better access to the DP and passenger header. The charge pipe wouldn't heat soak as much as it does hovering 1/2" over the DP, plus I think it'd be different and could potentially look pretty cool :cool:
Opinions welcome!
 

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Years ago I ran a custom box upper on a GT40 lower and saw gains over the GT40 upper. I do not recall how much but it was enough to decide to keep it on the car. Also do not recall dimensions but I maybe have a picture somewhere. It had the TB in essentially the factory spot.


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Discussion Starter #3
A pic of that would be great if you can find it! I'm not even too worried about any huge gains in power, I just would not want any significant losses down low just for the sake of getting my TB facing forward. If I lose a few lbs. of torque (like 5-10) i'm not gonna sweat it, the car spools up lower than I expected so I would guess it'll be ok.
 

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I found this one, not sure if I have any others. It originally did not have those braces welded over the top but we "cracked" things when we had it on a different car and were pushing things a little hard. Never had an issue with it after the braces. I actually sold it to someone on here but can't recall who, been many years.
 

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I tried a box with my Trickflow lower (93 GT). Lost 35 RWHP at same boost and RPM levels. Maybe if I would have reved the #### out of it, it might have payed off, but it wasnt worth it. Looked pretty though......
 

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I tried a box with my Trickflow lower (93 GT). Lost 35 RWHP at same boost and RPM levels. Maybe if I would have reved the #### out of it, it might have payed off, but it wasnt worth it. Looked pretty though......
imho, generally, this will be true for rpms below about 6,000. Shorter runner lengths want more rpm and the boost makes up for the restriction in the length of the stock GT40 uppers. Adding more plenum area of a box upper can also affect shift recovery in automatic backed engines so stall and gear are important to get right.
 

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is this what your thinking of?..


im in the process of finishing up this intake for my twin turbo explorer motor, just needs to be welded up.
 

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before you weld it, think about/measure whether you could weld some aluminum velocity stacks on each runner to extend their length............and if you do not, radius the edge of the runner inlets.
 

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Discussion Starter #9
is this what your thinking of?..


im in the process of finishing up this intake for my twin turbo explorer motor, just needs to be welded up.
Yeah thats pretty much exactly what I was picturing! How about some more pics?
 
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