Engine rebuild cost
 

This will be my first time having engines rebuilt and I am looking for ideas on what it will cost to have someone rebuild them with top quality parts. The engines are 96 502MAG MPIs. I would be interested in what it would cost to just rebuild the 502s and what it would cost to go up to 540s at about 600hp each (could be carb or fuel injection on the 540s)? I am guessing right now from what I have read on here about 5-6K per engine.

Jim

How many hours? Why the rebuild? If you have low oil pressure, a knock, or bad compression then fine. 502 mags can live about forever. If you just want to upgrade then ok. A 540 is about 4500. 502 rebuilds 3500.

This will help give you an idea of what it will cost to upgrade to 540's.

http://www.offshoreonly.com/forums/n...our-502-a.html

Contact Mark at Precision Marine. He'll take good care of you!

Thanks. I was ghoing to call them as they are only a few hours down the road from me. I have a friend who does all my work and I am going to see what he says as well. I am not sure if his shop does engine rebuilds though.

Right now my engines have 360 hours on them. My port motor has a loud metalic knock which we think might be my exhaust manifold gasket. The engines are going to be getting pulled for new Exhaust (Stainless Marine) so I figured since they are out I should either refresh, rebuild, or go bigger. I would not mind going bigger and N/A if I can get the 600Hp out of them.

Not knocking what your doing no pun intended but 360 is nothing on those motors. I wouldnt refresh until twice that. Now going bigger hell yeah do it. But if it's just the mani I would wear those out. Those stock motors are a joy and once you crackem open get ready for continual stuff.

I have 540's at 600 hp getting rebuilt right now by Wesco racing engines. Everything new execpt the block , crank, and rods. $8400 each. Includes dyno and paint.

I saw the AETCO ad. I would do the option of giving them my block and going with the 650hp choice for about 9k if I went that route. I really want to look at building them into 540s with top parts and getting at least 600hp from them. So far the cost to do that from what I see is around 6-8k. I am just trying to get a good ballpark number for upgrading to the 540s with top of the line parts.

We are going to do a leakdown and compression test when we pull them. I will know exactly what I need to do based off that info. Just trying to crunch some numbers so I can figure out how big of a dent I will put in my spending account.

Thanks

Jim

You can keep them 502's or bore them into 509's for probably half the $$$ of going to 540's and still keep the stock MPI. You should be able to get close to 550hp out of them.

360hrs on stock 502mpi's is nothing though. I wouldn't waste any $$ doing stock rebuilds as they should be good for at least twice that many hours. The only thing to maybe consider is to do some leak down tests and maybe valve jobs and head gaskets.

If you are thinking about going that route then you better plan on no less than about 12k per engine. The stock 502MPI intake and fuel system will not support 600hp NA and will need replaced. The 500EFI system barely supports anything over 600hp without major mods to it.

Thanks for all the great info. I may just keep them stock and do the valves/head refresh then.

Happy New Years to you

motor
 

with boring 502's into what cam do the go with and would you still be able to use stock exhaust

To use any decent cam that you would see a noticeable power difference with, you would need to upgrade the exhaust.

Not sure how married you are to EFI, but converting your engines to carb opens up some options.

Your engines with a nice cam upgrade, some roller rockers, single plane intake, and a 800 Holley, should make 525hp all day. some head work, and even more.

A buddy of mine had some 509's, Merlin iron rect port heads, crane 741 cams, Dart single plane intake, Holley 800 carb, CMI headers, made about 590HP at 5500RPM.

If it were me, your bottom ends should be ok with the hours on them if they were maintained. I'd pull both engines, clean them up, swap the cams, intakes, add carbs, , sell the EFI stuff, and enjoy some nice power gains. Simple stuff, that flat out works. Your stock EFI system will limit your power. Upgrading to a better EFI system, isnt cheap.

540's are nice, but most guy's think the extra 38 cubic inches are gonna turn their boat into a monster. Not sure the extra several thousand is worth the extra 50hp unless your building from scratch.

A properly spec'd 502ci is no slouch. :drink: