Has anyone made a 540 out of a 500 EFI and used the 500 EFI intake (not the MPI intake)? What were your results? Were you happy with them?

I have a friend that has, with some other changes. Heads, cam, and I think the throttle body.

Here are the results, full dress on dyno.

I had a pair of 565's with the 500EFI intakes that were extrude honed by ASM. Couldn't have been happier with them. Made about 700/700

You will need good heads, cam and exhaust to make good power, these made 630 hp on Brads dyno, the big issue is the intake and TB in stock form it stops flowing air

My plan is to go with Promaxx 317 worked heads, the intake is the Hardin Performance MPI with the ASM throttle body. Im told that it is the same intake as a reworked 500 EFI intake.

I guess the limiting factor in my equation will be my Gil Magnum Choice exhaust manifolds. Im told that they flow well, but have some reversion issues (any advice I would be grateful for)




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search some of Smitty's threads he's done a lot of testing on these with cut down runners and modded TB..........he'll probably see this and chime in.

I always thought this ad was a descriptive answer to your question:

Had almost the exact same numbers on a pair I built many years ago. Lots of port work in the intake to flow more air. Bigger TB. Compression, cam and ported Iron Eagle heads. My numbers were fully dressed, even my CMI's on the dyno with Mark Boos.

mine were 509s and at 640 hp/670 TQ.. its very hard to get much more than that. as everyone has stated, you will need cam, heads, big throttle body, good tune and most importantly a new fuel pump and cool fuel that can flow enough to feed it, the 500efi cool fuel has a very restrictive 90 degree at the end that goes down to a 1/4 inch id, that will lean you out... i did all of that on 87 octane as well.

You know for a reliable bravo pleasure boat those are not bad numbers on 87. Particularly if you look at the TQ curve.

We all talk about how the Mercury intake stops flowing but they knew what most of these were going in, boats that spend most of their life in the 3000-4500 rpm range, and in that range they are pretty strong feeling.

My feeling is if you want to get in the 700 range its just easier to go boosted.