Joe Gibbs 4.8 Radix question
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Joe Gibbs 4.8 Radix question
I have a 2004 RCSB Joe Gibbs Silverado with a 4.8 5-speed manual with the supercharger, Corsa exhaust and custom Gibbs tune of course. I know the fuel pump was upgraded with the supercharger option but I don't think the injectors were (someone please correct me if you know otherwise). Currently the truck is making 5-5.5 lbs boost stock and I want to change the pulley to a 3.4 or 3.2 (3.9 was stock for 4.8) to up the boost to around 8.5lb or 10.5/11lb debending on the pulley. Would you recommend new injectors stepping down to 3.4 pulley? I know going to 3.2 would most likely require it, but then a custom tune would probably be needed too. I don't wanna get too wild with mods, probably going to stop with pulley for now. Currents mods are shorty headers and Airaid CAI, on top of the factory Gibbs mods of course.
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Don't know what injectors came in your truck, but I'd bet a good custom tuner would tell you whether you were at or over your injector's capabilities. If you're running the stock tune, you're probably leaving quite a few ponies on the table even if you don't pulley down. A radix blown truck with a 5sp manny tranny has to be a lot of fun. I'm jealous.
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I Had a 4.8 5 speed gibbs (non-supercharged) and I put a Magnacharger 112 on it. My first mod was to pulley it down to a 3.25" pulley I belive and custom tune. It was a whole new truck. I can't remember if it ended up with 11.5 at that time. Can't recall for sure. I think my supercharger came with a 3.8" pulley maybe and around 8 psi boost.
Last edited by TurboGibbs; 03-03-2010 at 05:00 PM.
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LOL! It was fun. It is fun now, but I would be perfectly happy if I had the 4.8 & 5 speed back. The mp112 is the perfect size for a streetable 4.8. 5.3 it's ok and the 6.0, its too small IMO. But works well at stock boost.
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I Had a 4.8 5 speed gibbs (non-supercharged) and I put a Magnacharger 112 on it. My first mod was to pulley it down to a 3.25" pulley I belive and custom tune. It was a whole new truck. I can't remember if it ended up with 11.5 at that time. Can't recall for sure. I think my supercharger came with a 3.8" pulley maybe and around 8 psi boost.
EDIT: Should mention, this was for a regular truck with an aftermarket maggie kit, not a Joe Gibbs truck.