500efi throttle body
 

Does anyone know the cfm of the stock throttlebody and is there any direct replacements other than AS&M?

My guess would be that the stock HP500efi throttle body is about a 800-900 cfm throttle body. The single monoblade throttlebody that comes on the HP525efi is suppossedly a 1200 cfm unit. The bolt patterns and linkage arranigements are different for both, but you have a few choices. You could get the upper plenum off a HP525efi and mount it on your HP500efi with its monoblade larger throttle body or machine out the opening on your HP500efi top plenum and get an aftermarket monoblade unit like the ones Arizona Speed and Marine used to sell. Unless your engine has modifications like more cubes, bigger cam, or serious head work just adding a bigger throttle body is not going to add any recognizable power unless the engine has been modified to need a lot more air. Mercury Racing has not hindered any appreciable horsepower in these engines in original form.

Best Regards,
Ray @ Raylar

I took a 500efi 3 years ago, installed a 741 cam, new Dart Iron Eagle heads that were ported and milled .040. Installed a Cometic .027 gasket which got the compression from 8.75 to 9.25. I had the engine dyno by Precision Marine and it made 570 HP. That is a 100HP increase. That was with the Arizonia Speed Throttle body. While on the Dyno, the 500 Efi blade was installed and it lost 12HP. On a stock engine probally would not made 10HP. Keep in mind it takes 20HP to get 1 MPH. 1 MPH is not noticable.

Ray and Linster thanks for the replies I'm planning for next winters projects which will include heads,cam and computer reflash at that point I'm guessing my plenum and throttle body will be my next obstacle. Just planning ahead to see what options I have out there.

call tyler crocket , he has been working on a new top plenum and throttle body, early dyno numbers were a big improvement

nice job! Isn't a 500efi 470 to the prop shaft? so it might be alittle more at the crank.

I have Tyler Crockets set-up. It mounts the throttle body on the top of the intake. It is supposed to make 35-40 HP over stock. My engine will go on the Dyno in a couple weeks. I will let you know the HP numbers. Tylers set-up is $1000.00 with your old intake top returned as a core. jeff Wurl

Wow, a grand sounds like a deal, does he recal the ecm for that price also? that would be a awesome package

That price is just the throttle body,exchanging your top plate, and a couple of linkage pieces. Flashing your ECM is extra. I have some pics of mine sitting here, but cannot load pictures to this site. There is video of it on youtube. Just type throttlebody video in the youtube search box. Jeff Wurl

I would definately like to hear more about this setup , i have two 500 efis ,sitting there ready to install , and was digging through this section to see if there were any worthwhile upgrades (bolt on) worth doing..... this one definately sounds like a good one.