Difference between a 502/500efi/525efi
 

Other than the obvious............horsepower. Does anyone one know the exact internal differences between 502mag mpi, the 500 efi, and a 525 efi?
I am assuming it is mostly in the heads, cam and ECU but since I'm tearing down my 502mag to rebuild it, was wondering what the internal differences are and if it would be worth trying to duplicate vs. building say a 540 or putting a whipple on it.

Thanks for the input.

The bottom ends are all the same. heads on the 502 MAG and 500 are the same. The efi525 went to edelbrock heads. All 3 of course have different cams.

anyone know the actual specs on the different cams?

fixx
 

500 efi has the same bottom enf as the 502,the 500 efi i believe has a crane 731 cam, the 525 efi has a differant upper intake plenum that flows more cfm,the bottom end has k5 h beam connecting rods with a crame 741 cam..the blue engines are soppose to be blueprinted engines compared to the black engines.

If you are looking for more HP, I would look here http://www.offshoreonly.com/forums/d...e-results.htmland try to copy the build.
That is about as much HP as you are going to get out of a 502mpi without an intake manifold change and major modifications..

502 Mag
224/224 .478/.478
115LSA

500 EFI
230/236 .598/.610
114LSA

525 EFI
236/244 .610/.632
114 LSA

Thanks for the info guys!

HP500 has inconel exhaust valves and stainless steel intakes, whereas the 502 Magnum has stainless steel valves both sides.

MC

My 500 efi had Manley h beams with Mercury Racing etched on the side when Potter tore it down.

HP500 has a different intake than the 502 Mag MPI.

Also the 525 has closed cooling and no distributor.

Which heads are used on the 525's?

Edelbrock aluminum... I believe same as Performer RPM, not Victors though.

502MPI has stock crappy exhaust. Other two CMI's.
Intakes are different on all 3.

Almost forgot to add:

502MPI cost $
500EFI cost $$
525EFI cost $$$
:lolhit:

They switched to the Manley rods after about the second year of the 500efi.

I was waiting for that! :party-smiley-004:

now thats language we can all relate to.kinda like good,better,best.

Does a 502 mag mpi have forged internals? 1997

yes.

There casted/machined by Edelbrock, but they are not the same as the Performers. It has Mercury's own exhaust bolt pattern and the bosses on the front for the closed cooling. Intake and exhaust runners are quite different, the performers are actually better. These are much closer to GM iron head runner shapes. Don't really know why they didn't just modify the Performers to work...:drink:

ALL 502's have forged cranks, forged pistons, and at LEAST 7/16" GM forged rods (newer 500/525's have custom Merc Racing rods).

Performance:

502 +

500 ++

525 +++

So would running a 500efi or 525efi cam be too much for my 502?
I do have cmi etops but otherwise pretty stock until I put the sidemount whipple on.

The simple answer is no, its a great cam. With different heads and some other changes that cam (525efi) lives in a lot of 600++ HP engines.

The more complex one is that you would till need reprogramming etc to the 502. You can't just do a cam change on any efi engine, and not change the computer

I will be re-programming the whole system anyway when I put the whipple on, so that won't be an issue. I wasn't sure if the stock 502 heads would be okay with the more aggressive cam of say a 525.

They will be fine. HP is going to get you in the range of ~500.

Keep in mind that you are going to need to change the rocker arms to adjustable ones, the push rods, and the lifters