what cam kit do you recommend to a 502 1998 mpi/mag? (340hours)

Do you recommend lightning headers or emi thunder with the cam kit? hp gain?

Something else i need to do when i mount a cam kit?

I going to rebuild the engine this winter, some recommendations?

do you plan on having any head work done?

Better talk to somebody that can reprogram the ecm and see what they have already done and what they used. Otherwise it will become an educated guessing game when it comes to reprogram.

BTW, 340hrs is nothing on a 502mpi. It should not need anything with that many hours.

no, only get them checked,

Ok,

the engine use a litle oil,

maybe i dyno the engine, i heard 520hp with headers and new cam?

I would agree with Griff, unless you are ready to upgrade the programming and fuel delivery, be careful trying to get 500HP from a 502MPI with cam and headers only. You may end up with some running and durability issues. the cylinder heads and valve train should be reworked and upgraded with these types of addtions to really be effective and reliable.
As for headers or manifolds, I would suggest looking at the Dana Marine flo-torque header manifold kits as they are better at making power than either of the other two manufacturers you listed.

Best Regards,
Ray @ Raylar

You'll be luck to gain 50 hp with a cam, exhaust and a reprogram of the ecm. 50hp= about 3mph. If your prop isn't labbed, you could get 2 mph by just doing that.

All 502mpi's use oil. Mine uses about a quart of oil every 10-15hrs depending on how hard I'm running.

x2.

This has been a fabulous performing camshaft kit for our customers. It comes complete with Hyd. Roller cam, Hyd. Roller lifter, Valve Springs, retainers, locks, seals, and pushrods. http://www.keitheickert.com/detail.aspx?ID=2363

We have ECU remapping to match this camshaft as well http://www.keitheickert.com/detail.aspx?ID=336

You will want to add an adjustable fuel pressure regulator http://www.keitheickert.com/detail.aspx?ID=877 ,

a free flowing flame arrestor http://www.keitheickert.com/detail.aspx?ID=857

and a performance exhaust system
http://www.keitheickert.com/detail.aspx?ID=9197

There's no debate the lightning tubular header is superior in performance to the EMI exhaust manifolds hands down.

Best Regards,

Thanx

Hp gain with that parts?