Converting A 502
 

I have a stock carb 502 motor. I have been told all that is needed to upgrade this to a HP500 is a new cam and carb set up. Has anyone attempted this ? If so,what exactly neede to be changed,and any suggestions if someone sells a complet kit?


Thanks Paul

1Boatnut

You might want to do a search on your topic. There has been a lot of talk in the past on this subject.:rolleyes: I believe there is a lot more to it then just a cam and carb.:(

99baja342,thanks for the heads up,but where is the search you are speaking of ? here on the OSO board? I read in the back of hotboat that a engine shop was selling the kits. When I called they had no more and did not expect to get in any more. Acording to them it is only carb and cam that is the difference,but thats the reason I came to the board.Just to see if anyone else has any info. Thanks again,and any info you come upon would be apreciated.

the carb and cam woudl get the the extra HP and make it powerwise equal to an HP500.

However HP500 are taken apart and have all the clearances checked and so forth. It is eth only HP series engine taht isn;t blueprinted but i am am sur ethey check everything out and make sure it all matches before sendign it out as an HP 500.

As for the search use th OSO search feature adntype in HP500 and you will get aton of results. Thjis has been discussed to death here.

Cam - intake - some head work - carb and don't they use gill exhaust?

502 Conversion
 

I believe all the Merc Hi Perf Series engines have one piece valves instead of the stock, two piece GM valves your carbed 502 has. This might be critical with the new cam profile. They also use Crane Roller Rockers and roomier valve covers. They also use a different flame arrestor. There may also be a different thermostat. The HP 500 definitely uses aftermarket exhaust. The entire valve train is upgraded. These are in addition to the previously mentioned differences.

I'm certainly no expert. Call Rod Dash @ Performance Marine in Oshkosh, WI, if you want all the details from someone who deals with these motors everyday.

I believe I've heard that if you rebuild your 502 you may want to try a new and improved ring arraingement with new pistons. Add any trick/useful carb parts before you hit the water too. BG gaskets, see through bowl screws, etc. These might make dial in a little easier task.

Good luck in your project

The old HP500 carb'd motor can be built using the following equipment:

You start with your 502
add the old Crane hydraulic roller cam 169611 and related parts, ie; roller lifters, new push rods and use the Crane Gold roller rockers and the Crane triple spring 99886. You'll also need to get longer rocker arm studs and new valve covers to fit the taller rocker arm studs and seals to fit in the triple spring. The umbrellas wont work.
*If your engine doesn't have a roller cam now you'll need the lifter guides from GM #12551397 and the guide retainer #12551399 and 4 bolts to hold it down #9440224. Ps...use loc- tite on the 4 little bolts. Also, if you don't have a manifold oil shield, it'll help keep hot oil off the bottom of your intake, #12555320

While you have the heads apart, get them cleaned up, valves and seats re cut and get a 3 angle valve job, polish the combustion chamber, and exhaust porting. You want to take as little material from the combustion chamber as possible so your compression ratio doesn't fall too low.

Add a Dart intake (#41124...about $350)
A Holley 800 double pumper mech secondaries
and most importantly a set of CMI "E" top exhuast manifolds.

So, as you can see, there's alot more to it than just cam and carb.
If you do not have a roller cam and exhaust now, you're basically starting from scratch. In which case lets run down the cost, shall we?
Head work $500? depends on who you have do the work.
head gaskets 70
Intake gaskets 20
Cam 275
lifters 400
guides/retainer/bolts 50
rockers 265
springs/retainers 250
pushrods 125
seals 30
studs 55
Dart intake 350
CMI exhaust 3000...not polished add 500-1k for polished
Holley Carb 375
Valve Covers 150? They're tall covers wedged to make room for the exhaust.
So approximate total is: 5.....carry the 1.........well I better get the calculator....$5915

Still wanna build it?

Now, that's true carb'd HP500 parts. You could save about $1000 by not doing the head work and going with a different intake and valve train components. I didn't even add a new timing chain, even though that's only 25 bucks.

The biggest point is, it's not just a cam and carb change.

DAVE

GottaHaveIt; I think what Puder meant was that you don't have to wait for someone to respond to a question, you can look and see what has already been said about it. There is a wealth of info on this board. Take advantage of it. No reason you can't start a new thread with a question that wasn't answered previously.

Your question about the Edelbrock heads is good one. I would like to know more about them myself. A new thread, maybe?:cool:

Guys,thanks for all the imput. debotmon,Rod did contact me and was very helpful. I spoke with him about a year ago on another subject,and he was also very helpful then. I have gotten some good advice and now I need to check in my boat stash to alocate the funds. Dave F,your killing me.No just kidding. The good news is I already have the exhaust so that shaves about $3000.00 off of your total.If your calculations are correct,I only need $2900.00 for the job. Hell thats cheap considering I paid almost that much for the exhaust to get aprox. 35 more Hp.Thanks for all the part numbers,thats outstanding.I also think it already has a roller cam now. I am glad I started this topic (although maybee it has been asked before) but I sure found most of the answers I was looking for.

Thanks again guys

P.S-----anyone got an extra 3 grand?

gotta have it

cool out buddy.

I'm not sayin we can;t keep discussing it. I wasn;t even saying it has been beaten to death. I said "it has been discussed to death" meaning there is a ton of info not that we can;t keep talking abotu it. When i start a new project i ask questions of course but i also search the archieves to fidn previus info then I print ALL of it out and start working and any question that arise (and weren't previously answered) after reading it all i ask in the new thread.

So feel free to keep asking questions. I was just saying you can find a wealth of knowledge already in the archieves and can read it right this very moment without waiting for replies.

Dave F has a goodlist but I would not put this much work in with out changing to one piece valves. You could go with good stainless valves for this application and they would flow better than Inconel in my opinion. There is more HP to be had if you change heads. Cam choice would depend on heads used and or how much flow work is put in to stock heads. You could use stock valve covers if you break or grind off the drippers. You may need to double gasket valve covers or take about .060 off of adjusters for roller rockers but it can be done. New covers look cool though. Sounds like a fun project. Are starting with a base 502 or 502 mag motor.

UM Paul,,,, you can't make a HP500 out of a 4.3 V-6.:D :D :D

I was wondering how long it would take before I would see you post some crap, and its a 3.0 Study this well,cause your gonna help>

I don't know if he has two piece valves or not. I was under the impression that all Chevy intake valves were 1 piece, and Merc uses the Inconel one piece exhaust valve. But hey, what do I know? If so, I agree, 1 piece is the way to go.

Yes, I absolutley agree with bigger power gains with different heads, but that's another 2g's.

Glad I could help. It was pretty easy though, I just had to pull out my receipts from the last time I built one.

DAVE

Help,,,, **** I end up doing all the work so you don't screw it up, and then I have to tow your ASS back !!!! HEHEHE Almost spring !!!!:D :D :D

How many times have you towed me? You are usually so far out in front of me you dont even realize I am dead in the water> But if you insist on doing all the work,you know where the boat is,so what the hell are you waiting for?

500 longblock
 

Rod

I have two 1997 500 HP longblocks with approximately 50 hours each since rebuild for sale - intake to pan $5500 each.

920-236-4220

I already told him about your motors Rod,,, but see,,, my buddie Paul here squeeks when he walks he's so cheap !!!! We could go through his for under 3k,,, including heads, but there is no need because he is so much faster the me now !!!! ( anyone noticing a trend here LOL !!! ):D :D :D

1 boatnut if you already have the block and exaust to start why do you only want to duplicate the HP 500. I started with this combo used stock GM heads and flat tappet cam, Weind intake and Lightening headers an made 547 HP at 5100. I have Dyno sheets to back it up. This winter changing to Dart intakes and a little carb work and are expecting 600. The block is stock and the heads have had no portting just a good valve job with inconel valves, the correct springs for the cam and Harland Sharp roller rockers. The motors are totally reliable!

B.R.S ,that is certainly something to consider.I just dont want to get too radical,because as you stated I really want something that is totally reliable.Did you use the stock 502 Carb? What year is your block? I believe mine is a Gen V ,and I was told it already uses roller rockers and cam. Anyone know this to be true ? Not that I am not going to change them,just interested.


Rod,the longblocks you have might be a option ,but I also was kind of looking forward to this project. Thanks,and I might be calling you either way,for the parts too!


obnoxus(Dennis) as far as sqeeking when I walk,I learned from the best. YOU!!! I also like to refer to it as currency conscious. Also if I already were so much faster than you now I would save the 3-5 grand for fuel,since I burn twice as much as you do. DONT make me start posting picture ( with you always in front ) cause you know I have them.

Guys,again thanks for all the imput. It has helped me alot. Any more input would still be apreciated. EXCEPT from you Dennis.

Sorry guys just having a little fun with a ex buddy. :D :p ;)

EX BUDDIE !!!!! Yes sure,,, ex until the motors apart in the driveway and your scratching your head,,, then it will be time to " rekindle " things huh !!!!

I mean hey,,, we rebuilt your outdrive in the driveway at midnight,,, how bad could the motor be with us planning the job !!!!!

Paul,
I can't believe your letting Dennis pick on you like that.
Go ahead and build that motor up and KICK HIS A??.
Besides I always like seeing a good race.:D
Spring is on its way!!!!!
Mark

500 hp
 

Hey guys

Dont forget the 500 hp has 2.250 intake valves, also the older ones have some chamber work although I dont think it's worth any power gain.

If you have a GEN V 502 it is not a roller cam engine. Easiest way to w/o tearing into it is by looking at the timing cover. Mark IV and Gen V have a steel timing cover. Gen VI roller cam engines have a cast aluminum cover with only 6 bolts. Non of the Mag engines from Mercury have roller rockers.

1 boatnut I use 830 Holley vacume secondarys. The dyno sheet said the jets were 82/82. A little soot on transom but the plug color is perfect. I dont know what year the blocks are but they are Gen V. Mine has flat tappets but I have heard that some of the later blocks are machined the accept GM roller drivetrain but I have never personally seen one.

I love racing Paul to Mark !!! Even if he is out in front he breaks before we get anywhere for someone to see him winning !!!! ( sorry buddy ):p :D

Guys,again thanks for all the info. I am really getting a good feeling for this project. ANY more info would sure be apreciated. It is great to see all the different opinions and experiances everyone has posted.





P.S -Mark,I am not letting Dennis get away with anything. Believe me he will PAY!:D I figure if I spend a little dollars,this will upset him enough to get a crowbar out and pry open his wallet. He will either spend twice as much as me or buy a new bot, Both of which will make me the WINNER!!!!! Say hi to Patti,and hope to see you guys on the water soon.

Heck yes !!!! I might even spend some of my comunion money (which Paul swears I still have) to pry a couple more ponies out of my little slug !!!!

By the way,,, get your motors back yet Mark? Let me know if you need a hand getting ther Cig back together.

I hear ya Paul, There is a secret mission ther I'm sure.

Dennis I don't have the motors back yet they are probably 3 to 4 weeks out yet. They are waiting on some parts and need to do some machine work on the blocks. Been working on buffing and waxing and cleaning the bilge and stuff like that. So once the motors are back I should have them in the boat in a couple days.
Thanks for the offer of help I'll let you know.
Say hi to the girls and see ya all soon.

Mark

I'm off the board a few days and miss all the fun. Some of these posts have been very constructive. I LMAO to the others.:D
See you guys in a couple weeks.
Dan

hp500
 

don't foget with the dart manifold you have to use staggered jetting in the carb

Here is another option
 

For a little more money, why not supercharge your existing engine. I put a ProCharger on my carburated 502 that had over 125 hours on it. I kept the boost down to a conservative 3.5 lbs, although I'm told that 5 lbs would still be ok. Since its intercooled, I did not worry about making any internal engine mods. Now the boat has over 200 hours, and has perfomed flawlessly (both engines). The boat is a 93 32' Fountain, and last summer I raced several new step bottom boats with either 502 EFIs or 500 HPs and beat them.

Just a thought.

PS. you forgot to add new props to your total $$ amt.

Got The Fever, a good thought it is. I have been giving it some thought and might just do that instead of the other up-grades. What kind did you buy,and what was the cost ? Also I did not forget about the prop,I have been looking. What pitch did you have and what did you have to jump up to ?

Yes definatly the blower,,, this way when I get you to over rev it to beat me it will REALLY come apart !!!!

Procharger means we are back to putting inconel valves in it by the way.

Mark,

Come do mine when your done !!! a 27' should be no problem for you after doing yours !!!!

Like I said,,, need help,,, don't be shy,, glad to help.

Where's Patti been hiding?

The good thing with the blower is I wont be forced to over rev to beat you . I just will beat you.

obnoxus,
It's called a rev limiter. The cheapest piece of mind I ever purchased. In my case, the Mallory Soft Touch. You can change out the RPM where the limiter cuts in simply by swapping out a chip.

I purchased a Stage I, since I was not going to go crazy with the boost. I also saved a little money by Not going with the polished model. If I remember correctly, the Procharger itself was in the $3,800 range(each), but this was 3 years ago. I also had to purchase a different carb (Holley 750). The prop change was not an apples to apples type change. I went from a Spenelli 14"x27" to a Bravo 15"x28" (I forget the exact diameters, but am sure of the pitch). I was also going up in elevation by about 3,000 feet (one of the reasons for adding the ProCharger). I did all of the work myself. It is easy enough for any mechanically minded person. The tuning, however, is another story. Just be patient, and don't go too lean.

Let us know what you decide.

Fever,

You don't have to try to convince me, I have a rev limiter on my boat !!!! It's that cheap guy with sunshine as his avitar we have to work on.

To slightly edit a line from Days of Thunder,,,,,, When the little needle on the tach goes into the red and reads 5,800 RPM,,,,,, That's bad !!!!!!! ( at least for a stock 502 !! )

A what limiter ? Obnoxus convince me ? Have not blown a engine yet from over revving. As you seen on my last outing with you, push it to the limit, and then got you to fix it:D Lifes short,why not get through this one as fast as possible ?:eek:

Paul,,,,,, anything that gets you to spend more money makes me a happy man !!!!!