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Converting A 502

Old 03-07-2002, 04:04 PM
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Default 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
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Old 03-07-2002, 04:46 PM
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You might want to do a search on your topic. There has been a lot of talk in the past on this subject. I believe there is a lot more to it then just a cam and carb.
 
Old 03-07-2002, 05:36 PM
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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.
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Old 03-07-2002, 07:13 PM
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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.
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Old 03-07-2002, 08:45 PM
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Cam - intake - some head work - carb and don't they use gill exhaust?
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Old 03-07-2002, 09:33 PM
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Default 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
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Old 03-07-2002, 09:48 PM
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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
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Old 03-07-2002, 09:51 PM
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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?
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Old 03-07-2002, 10:26 PM
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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?
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Old 03-08-2002, 12:07 AM
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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.
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