which engine one or the other or both requires the most maint. for reliability and trouble free operation?

I would defintely get the 500. It is just as tough as the 502 and has more hp.

The 500 has better internals...such as bigger better vavles, 2.25 Stainless and 1.88 Inconel, J.E. forged Aluminum pistons and Crane roller rockers.
The cranks are GM forged steel and are Tuftrided...I don't think the 502's are but I'm not sure.

4 YEARS WOT NO FAILURES. HP500EFI.NO DOUBT

500EFI hands down. If you have the cash... 525EFI.

Love my 502's. . . would trade 'em for HP500EFI's in a heartbeat.
In fact, it would take a team of the Best and the Brightest from M.I.T., with their most advanced technological equipment, to be able to actually calculate how quickly I would make that trade.
And I love my 502's.

No brainer.... 500's

One 502Mag doesn't have enough for the 26 Sonic.
I have a friend with one... and it's a dog planing off real GPS top end is 64, which isn't too bad considering what motor is in there..

Go for the 500 if you can go the extra cash...
You'll never be upset if you have "too much power", but you'll be really pissed if you don't have enough.

What is the internal difference between the 500-EFI and the 525-EFI?

Roby

26Sonic,

I have owned both and go with the 500efi, it sounds meaner is faster in hp and rpms, just all around better motor. Plus you will always wish you had it if you go with the regular 502.

Will