502 Build??? Need advice!!!
 

I purchased an complete 502 mpi Mag 1995 that needs to be reworked to replace my 310hp 454.

I want to keep EFI/MPI but pump the power up. Im figuring an 509ci, get headers, roller Cam kit & reprogram, Free flowing air filter. How much can i get?

Would like 500-575HP but from what I have read. Its about 500 max w/ efi unit? What about fuel rail/injectors? Whats the best performance header for salt water? Im no opposed to doing other mods just would like them to be worth the HP.

Just to give you an idea. I have dart block 502's that are actually 509's with 250 B&M blowers and I have 605hp at 5500rpm. I have to use super unleaded. Also, my engines are rollerized. Single 850 Holley Carb. I heard you can get about 600hp if you bore it out to 540 cubic inches and have aluminum heads and the right setup, no 250 blower.

I am just starting to look at the same thing so I am very interested in how this thread develops. I am looking at the Whipple package. About $7k. Their website says it is a direct bolt on to the 502 Mag and good for about 600hp, ecm reprogramming included. I have don't know what other mods are necesssary like cam, rotating assembly, heads, exhaust, injection, or whatnot. Does anyone else? Anyone done this upgrade?

I dont have any input but interested to see how the thread turns out. I am kind of a believer that if you want good reliable power then you are not going to bet "bolt on" power. I am almost positive in saying that if you want a blower motor, then build one for that intention. I think the idea of "bolt on" superchargers is misleading and will leave you in a mess at the end, but just my 0.02.

I build 540 motors on the side for something to do. I am a retired pilot and I have built several 540's using a dart Big M block, Callis stroker crank, Manley H-beam rods, JE pistons, Total Seal rings, Custom roller cam and Brodix aluminum heads with Manley stainless steel valves and inconell on the exhaust. My average dyno numbers are 650 HP with a single Holley on top and no supercharger at 5500 rpm. The compression ratio is approximately 9.6 to 10.0 and you will need to use 93 octane. I dont see where I can add a pic for you of the dyno sheet, so if you are interested in one...you can email me at [email protected] and I will send you pics. I can also send you a link to my best buds motor that I built for him 2 years ago along with a dyno sheet. This motor is very healthy.

Call Ron I'm sure he will be very helpful with your questions

941-758-5942

I agree about not just bolting on power. All the internals need to be changed if you want something reliable. From a thread that I posted several weeks ago about what I can do with my dart block 502s, I found out that if I bore my 502 block to 540, change all the internal, get aluminum heads, add a Whipple 3.3 Blower with Intercooler, add more fuel and I should produce between 900-950hp. You will have to change out everything though. I am planning on doing this to my 1994 Cigarette TOP GUN. But I have to get new drives first. I will destroy my bravo 1's. I am going to go with Arneson Surface Drives when I can afford it.

Ateco has a few choices that are work very well.
502 into a 540
502 kit that makes 625 hp no blowers.

http://www.offshoreonly.com/forums/n...502-540-a.html

http://www.offshoreonly.com/forums/n...c-500-efi.html

Do you have a tune for the +125 for 500EFI setup that will work on a 502MPI? Basically using everything in that kit with exception of MPI induction instead of 500EFI induction

540 is not in the cards now. I pulled both-complete motor/1 short block down tonight. Both are in really good shape. Either a EFI motor or build an carb motor? Leaning toward an EFI still. How to make HP500-575 Is the question? Where is Raylar-Young performance-other experts?

All you need to make 575hp out of an HP500 is a good head and cam combo.

Griff - I can put the 502 mag efi/mpi back on and make 575HP? Or convert my 502 to an 500HP = 575HP?

I'm here:grinser010:

You should be able to make approx. 550 using the 502 mag intake. The 500 efi intake is a better unit to start with, but you can use the 502 mag intake, although you will give up a little power. I would add some cubic inches if the bottom end needs to be freshened up. You can take it to a 516 or 524 very easily. This will still leave plenty room for future rebuilds. If you don't have to freshen the bottom end, then a cam change, increase in comp. ratio, some head and intake work, and programming will get you 525 - 550hp. If you do the bottom end and increase the inches, then you can make 550+hp.
On the other hand, if you change the intake to something like the Holley setup, then you can make 575+ with cast iron heads and well over 600hp with aluminum heads. I really like Holleys efi setup and use it often. It is a single plane intake with injector bosses casted into the intake, 2000 cfm throttle body, injectors, rails, etc. It runs around $2500 (without electronics) and is worth every penny. This will also be a great platform for future upgrades. I have made almost 800 hp with this setup on a 598.
Bottom line....you will be able to make more power if you go through the bottom end and increase the cubic inches. I still think we can get real close to your goal without doing that. It all depends on how much time is on the engine. Give me a shout if you have any more questions or if I can help in any way. Thanks.
Eddie

Here are a few pics of the Holley setup on a 540 with aluminum heads. This one made 701 hp.

John I sold all my 500 HP parts but we can discuss what to do. Look at your PM's.

If you carbed, you can make 575+HP with a good head and cam combo. Using the stock 502mpi injection will limit you as eddie said.

I am curious about the electronics for the Holley EFI setup. Can the Merc box be reprogrammed, or do you need to change over to a MSD (or other) unit? Also, what about exhaust - at what point does the stock Merc exhaust become a limiting factor?

I only use the Mefi ecm on the engines that I build. That is why I buy the Holley setup without electronics. I don't think Holley's electronics are that good, especially in a boat. I use a Mefi 4 now, but have used a 1, 2 and 3 in the past. I use them because I think they are the best. They have the benefit of excellent knock protection.
As far as the exhaust, the stock setup becomes a restriction on any thing other than a stock engine. On some stock engines, they are already a restriction. I am referring to the stock manifolds. If you have a 500 or 525 with CMI's, then that is a different story.
Eddie

I am going the route described by Eddie. I am turning a 509 into a 540 (melted a piston) and will be getting the Holley intake and using my MEFI4. I have to say that working with Eddie has been great and he is very meticulous about building a motor which will be rock solid. If your looking for a builder then he is the guy.
Shane

OK ... this is going to be a real rookie question but ... MEFI = MSD or MEFI = Mercury?

Uh.....yes.:drink:

The Mefi (1,2 and 3) was used by Merc. for a long time.(10 years or more). Merc. never did use a Mefi 4. I think that Volvo and maybe Indmar or someone else may have used it, but Merc. never did. MSD does sell a Mefi 4. It is the same one that I use, except I do not get it from MSD. There are several versions of the Mefi 4. (4, 4A, 4B, 4C) Most people use the 4B.
Eddie

Thanks buddy. I will send you a few more pics as soon as I finish buttoning up the bottom end.
Eddie

Decision Made! Unless some one can give me another provin combo?
 

Decision Made! Unless some one can give me another proven combo?

Building the Stock 502 Mag efi then selling it! Selling my present 454 MPI. Then building a 502ci, 850 Carb, Aluminum AFR head, high rise intake, custom cam combo that Thunderstuck is running= 600HP.

Any other proven packages they would like to put out there for consideration?? Open to IDEAS!

THanks for the advice.

Who is building it???

Assembly
 

I will have the short block assembled then assemble the rest my self. I might even assemble the short block. I will dyno & test the motor @ a shop close by. I have done small blocks but have never done a BBC. Blocks are @ the machine shop getting honed & new cam bearings. I know ur in the business. What services do you have to offer?

That young link takes you to a domains for sale page..

What pistons are those in the pictures. They look like they have a small dome.

Thanks. I need to look into what the hell is going on. My site has had that domain name for years. I will be on that today.

Those pistons do have a small (10 cc) dome. They are made by JE

Powerquest, I pretty much do it all from custom engines, drives, rigging, tuning efi and carb, etc. Give me a shout if I can help you in any way.
Eddie

Havent seen the link thingy you are referring to, but to protect yourself...go to your court house and register your stuff under an assumed name. I have done all my stuff this way and have only had one issue. When I showed the people the documents that I had everything registered, the piss & moaning was over.

Would you happen to have the JE part number for those pistons and are they for a 540?

The pistons are actually for a 547 ci. (4.25 stroke, 4.530 bore, 1.27 CH). The number is 212162.
Eddie

Where are you getting the CAM and what is it?