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Hp500efi rebuild

Old 07-08-2020, 10:08 PM
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Default Hp500efi rebuild

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.
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Old 07-09-2020, 12:38 AM
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Stock EFI intake hits a wall around 600-620hp
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Old 07-09-2020, 08:23 AM
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These 540's made 630hp, thats all the intake will support


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Old 07-09-2020, 08:29 AM
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Originally Posted by F-2 Speedy View Post
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
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Old 07-09-2020, 08:41 AM
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This can be done for 13K, looks like more power available with added services.



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Old 07-09-2020, 09:43 AM
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Originally Posted by riverrunner242 View Post
I'm assuming bigger injectors? Any idea what I would need to use if I decide to use the efi
65 lb hour injectors, stock TB and intake runners, custom grind double swap cam and AFR heads
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Old 07-09-2020, 01:29 PM
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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$
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Old 07-09-2020, 01:31 PM
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Originally Posted by F-2 Speedy View Post
These 540's made 630hp, thats all the intake will support

Did you have the FA's on when you dynoed? I saw a restriction from them at less hp on my dyno
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Old 07-09-2020, 01:47 PM
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Originally Posted by articfriends View Post
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
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Old 07-09-2020, 09:38 PM
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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.
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