I recently bought a hp500efi and looking to build a 650 hp 540ci out of it. I'm curious what other guys are running. Retuning the efi system, carb, or installing aftermarket efi system such as holley. As always I appreciate all the help I can get.

Stock EFI intake hits a wall around 600-620hp

These 540's made 630hp, thats all the intake will support

I'm assuming bigger injectors? Any idea what I would need to use if I decide to use the efi

This can be done for 13K, looks like more power available with added services.

65 lb hour injectors, stock TB and intake runners, custom grind double swap cam and AFR heads

a 525 style flame arrestor with a monoblade tb properly tuned will help a built 500 gain about 15 to 20 hp on top and more peak torque. The FA's are super expensive at 765$ each though. You CAN buy the 525 throttle blades for 50$ to bore out IF you know a competent machinist . hardin or somone sells a 525 fa for 600$

Did you have the FA's on when you dynoed? I saw a restriction from them at less hp on my dyno

yes, full dressed with CMI sweepers, maybe we should of taken them off and do a pull, but we didnt

I honestly thought someone would have suggested selling the HP 500 and just buying a 540 as opposed to conversion.

A lot less work and prob cost less in the long run too.

https://www.ebay.com/itm/MerCruiser-...QAAOSwjL5ZFdX3

https://www.ebay.com/itm/540-Bulldog...IAAOSwnK9ZVqxK

https://cleveland.craigslist.org/bpd...145891904.html

Just curious, what did you buy the 500 HP for? I've got a 502 MAG (black engine) that I would ultimately like to upgrade and a 500 HP EFI would be what I'd want or replicate for reliability.