diveboy

I was wondering if anyone could recommend a good set of cast iron aftermarket heads for the hp500efi? I would like to go with an Aluminum head but simply can't afford to. I need to save some cash to upgard cam, and injectors, and reprogram the ECU. What iron head will yeild good results (if any) keeping mind the other changes I'll be making to the motor. What results (hp/torque) are you guys seeing from these upgrades? Any cam recomendations?

Thanks much in advance!!! You guys always seem to offer great advice.

Diveboy-

Truckin

Air/Fuel mixture velocity is not a major concern when you are injecting fuel into the engine with 30 - 40 PSI at the intake port.
A modified EFI engine will run just fine with the stock rectangle port heads. Unless you are really planing on kicking up the horsepower level with a big camshaft, bigger fuel injectors, bigger intake manifold, exhaust headers, high rpm etc, increasing the intake port volume (size) will not show much of an improvement and reducing the intake port volume (to increase port velocity) is not necessary with fuel injection.
Sincerely
Dennis Moore

diveboy

Thanks Dennis!

I would like to see a minimum of 600hp. I was planning on changing the cam, and possibly the injectors (if the stock ones are too small). Can I get there with the stock heads? I was considering running the motor up to 5600rpm.

Thanks agian!

Truckin

I don't think you can get 600 HP at 5600 rpm with a camshaft and EFI mods. You will need at least 6000 rpm and a compression ratio increase for the big camshaft needed to get you there. The stock rectangle ports heads will be fine.
Good luck!
Dennis Moore

bobby daniels

We used merlin heads ,,741 crane cam ,,AZ.speed e c u ,, I think 9 to 1 comp and kjlled 600h.p on a 509 cheap and fast ,p.m,
blown 1500 if you want dyno sheets ,ect.

liquid lounge

Diveboy: listen to Truckin...especially if money is a concern. That long runner efi manifold is already on the ragged edge with the current stock cam and going larger on the cam will quickly diminish the idle, tip in, and low rpm characteristics that we enjoy in efi engines. If anyone is suggesting that the 741 is a good canidate for an upgrade to this engine...
If anyone had a viable 100hp upgrade [excluding supercharging], for the HP500 efi, they would be rich and it would be easy to find.QUOTE: "JUST TRYING TO SAVE YOU MONEY " except I'm not trying to sell any item or service.

KAAMA

Hi Liquid,

So what you are saying is that the INTAKE MANIFOLD on the Merc 500EFI engine is pretty much at its FULL limit on this engine? In other words, the intake manifold cannot really be modified to move more air to support 600+hp---right? You're saying the intake manifold itself is the limiting factor here no matter what heads, cam, or injectors are added and that it is almost impossible to get much more HP out of the Merc 500EFI---correct? The reason why I ask is because I think I have heard this a few times before from other sources. I once knew of a guy a few years ago who sent his brand new Merc 500EFI's down to John Lingenfelter's shop and they could only FEASIBLY get about 540-550hp or so out of those engines and he is one of the EFI kings and knows his stuff! I was told that the Merc 500EFI intake manifold was the limiting factor. I'm NOT arguing, but rather I just want to make sure I understand what is being said here. Thanks

Mark/KAAMA

rpm

Please post or email me dyno sheets showing A/F ratios, bsfc, fuel flow and exhaust temps along with dyno correction factors. I'd also like to know the cost.

Thanks

Rod