Pulley size

Hey fellows, I just did a CAI and canned tune on my 2103 GT500. I am about to change pulley size, get a metco idler set up, and upgrade the throttle body before I take her to Kurgans for a “good” tune. Also gonna switch to a lund ngauge maybe for the device. My questions are: isnt it better to go with the lower pulley/balancer instead of the upper pulley swap? I can only go with a 10% lower so I dont interfere with the performance pack oil/line set up. I also want a better throttle body. It looks like the 65 or 67mm twin ford racing looks good for performance and drivability. Is there a better choice? Also want to install the off road x pipe with borla super snake mufflers. I want to stay as safe as possible, because I have obviously said good bye to my warranty at this point. Does this sound reasonable or is there a better plan for basic bolt ons with the trinity? Thanks for any input.

Chancey said:

My questions are: isnt it better to go with the lower pulley/balancer instead of the upper pulley swap? I can only go with a 10% lower so I dont interfere with the performance pack oil/line set up.

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Honestly, I don't think it makes a difference. People argue with me that it does, but the blower ratio doesn't really change where one set up is better than the other. A larger upper would be less susceptible to slipping, but a lower isn't exactly a cheap proposition. An auxiliary idler can get the needed belt wrap on the upper. Even the 10% requires clearance on the timing cover. I'd go to the 2.4" and if you need more boost, get the lower, or better yet apply that outlay to a bigger supercharger.

Chancey said:

I also want a better throttle body. It looks like the 65 or 67mm twin ford racing looks good for performance and drivability. Is there a better choice?

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Unless you can get one used at a decent price, I'd go for the new VMP 69mm twin if you're buying new.

Chancey said:

Also want to install the off road x pipe with borla super snake mufflers. I want to stay as safe as possible, because I have obviously said good bye to my warranty at this point. Does this sound reasonable or is there a better plan for basic bolt ons with the trinity? Thanks for any input.

Click to expand...

I'd hold off buying any aftermarket mufflers with an off-road pipe, until you get an idea of how loud the car will become. The loss of the cats adds a lot more volume than you can imagine.

Catmonkey said:

Honestly, I don't think it makes a difference. People argue with me that it does, but the blower ratio doesn't really change where one set up is better than the other. A larger upper would be less susceptible to slipping, but a lower isn't exactly a cheap proposition. An auxiliary idler can get the needed belt wrap on the upper. Even the 10% requires clearance on the timing cover. I'd go to the 2.4" and if you need more boost, get the lower, or better yet apply that outlay to a bigger supercharger.


Unless you can get one used at a decent price, I'd go for the new VMP 69mm twin if you're buying new.


I'd hold off buying any aftermarket mufflers with an off-road pipe, until you get an idea of how loud the car will become. The loss of the cats adds a lot more volume than you can imagine.

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Got it. Im gonna go that route on the throttle body and the pulley then. Thanks Catmonkey.