who has a kit with the best gains for a 500 efi 2001 without supercharging?

I would say leave it, or whipple it. No real in the middle with out pulling the motor apart, and then your at as much as a whipple would be but don't have one.

My 2 cents

WILL

brodix heads and ecu reflash..... 10k id guess

Your best bet is Mark at Precision Marine in Kenner,La(504-469-7463),he can do 600 or 640 pretty reasonable and dependable.He can dyno and tune the ECU and if needed fine tune it at the lake.Rob

Do a search on posts by "Linster" . He has done some nice upgrades to the guys local here in Richmond. I think he has built 6 or so 500EFIs into reliable 600HP/700TQ bulletproof motors with NO BLOWERS.

The Arizona Speed & Marine monoblade throttle body is a nice mod to start with. Then you need to talk about the ECU. After that, there is not much left without going inside, or supercharging.

I guess lower but it's been a couple years since I bought mine. This will give you a bullet proof setup with a nice increase in HP. If you get ambitious, look at cams. Short of getting blown, this is probably your biggest bang for the $. Just my .02

Each set of heads, polished and ported and built by someone who knows what they are doing...will run you about $5k all said and done. For both motors, labor, ECU flash...you are right around $10k as Ted suggested. I recently spoke with Dean Gellner about doing this to my motors...

Call Bill at Ateco (847)623-2737. Has a bolt on kit good for 600+ HP includes the reflashed ECU. Under $ 5,000.00.

Do you know exactly what they do to get 600hp with bolt on mods ? And, what is the reliability and longevety consequences ?

Where is Dean when we need him???

Tyler crockett is supposed to be finishing bolt on plenum tops with a built in throttle body that is re-located, He is having these casted at a foundry and will have them on the market soon. In intital testing he made 630 hp on the dyno with other mods,Smitty