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Rotarydave · 01-11-2009, 05:30 AM

I have a couple of the Atkins Set-ups and have done quite a bit of butt-dynoing as well as some engine dynoing as well. I currently have a custom set-up that yeilded a peak Hp of 301 at the flywheel, now before anyone cries BS.... it was done with high octane racing fuel, very expensive NGK Racing plugs, Holley 650, 5 inch (fresh rebuild very tight spec) camden supercharger with a -11 pulley (not recommended for street use), the engine is a 6 port 13b s5 cast irons, new rotor housings with a monster exhaust porting, no internal intake porting but the camden intake was port "modifed" to remove restriction and the external intake ports on the cast irons were ported some. The goal was to prevent any additional overlap allow extra exhausting time and reduce the time of intake restriction(hence the expanding of the ports externally). With the -11 pulley it created a max boost of about 13.5. Now this is not an extreme increase from numbers quoted previously by Atkins in other locations but I think that the engine modifications will allow it to survive longer. Everyone told me my previous engine wouldn't last, something about a stock S4 NA rebuild with s/c and 10lbs boost continually launching at 4k rpms but not shifting until 10k... decreases engine life... don't know why not like i was abusing it or anything..... BTW old engine go BOOM but not until many passes and 10k miles, I asked Atkins to rebuild it, they said I needed another core as there was nothing left of it. Oh well....

Back on topic, I have used both the 5 inch and the 7 inch, I prefer the 5 inch although the 7 inch can rev higher it takes more engine power to do so with the smaller mass the 5 inch does it faster but can go as high, at 10k rpms with a -10 pulley the 5 inch starts to cavitate and won't push more air (as indicated by boost drop) but it does get there in really big hurry due to the dramatic increase in low end torque, plus if I leave my foot out of it I can see 30 mpg. I hope this helps and if anyone wants to verify this with Atkins go ahead, the engine was installed in 2004 and just died late last year.

01-11-2009, 05:30 AM	#27
Rotarydave Rotary Nut Case Join Date: Jan 2009 Location: Cibolo, TX Posts: 273 Rep Power: 17	I have a couple of the Atkins Set-ups and have done quite a bit of butt-dynoing as well as some engine dynoing as well. I currently have a custom set-up that yeilded a peak Hp of 301 at the flywheel, now before anyone cries BS.... it was done with high octane racing fuel, very expensive NGK Racing plugs, Holley 650, 5 inch (fresh rebuild very tight spec) camden supercharger with a -11 pulley (not recommended for street use), the engine is a 6 port 13b s5 cast irons, new rotor housings with a monster exhaust porting, no internal intake porting but the camden intake was port "modifed" to remove restriction and the external intake ports on the cast irons were ported some. The goal was to prevent any additional overlap allow extra exhausting time and reduce the time of intake restriction(hence the expanding of the ports externally). With the -11 pulley it created a max boost of about 13.5. Now this is not an extreme increase from numbers quoted previously by Atkins in other locations but I think that the engine modifications will allow it to survive longer. Everyone told me my previous engine wouldn't last, something about a stock S4 NA rebuild with s/c and 10lbs boost continually launching at 4k rpms but not shifting until 10k... decreases engine life... don't know why not like i was abusing it or anything..... BTW old engine go BOOM but not until many passes and 10k miles, I asked Atkins to rebuild it, they said I needed another core as there was nothing left of it. Oh well.... Back on topic, I have used both the 5 inch and the 7 inch, I prefer the 5 inch although the 7 inch can rev higher it takes more engine power to do so with the smaller mass the 5 inch does it faster but can go as high, at 10k rpms with a -10 pulley the 5 inch starts to cavitate and won't push more air (as indicated by boost drop) but it does get there in really big hurry due to the dramatic increase in low end torque, plus if I leave my foot out of it I can see 30 mpg. I hope this helps and if anyone wants to verify this with Atkins go ahead, the engine was installed in 2004 and just died late last year.