ballon78

I have read like 20 pages of searches and still really not sure.

Im swaping from a 1998 454 motor to a brand new 502 Base Marine motor from www.1800runsnew.com. My old motor was a gen 6 but not sure if it was a roller cam motor, i was told it was....the casting numbers come up as 10237297...454.......96-up...4-bolt, Vortec 7400", "L-29" Gen.VI. It was carb and i think 330 hp. how do i know what the 502 base crate motor really has for a cam/gear....i can see it but dont know how ro tell if the cam is billet or gear is a press on cast?? I want to make SURE i dont put in my old distributor and it eats the gear up and need a tear down. Do the GM marine base motors have a GM cam in them...who makes them?

I was hopping that if my old 454 had a roller cam then i should be fine in the 502 but not sure what they use in the 502 for a cam as its a gm base marine motor. Its impossible to find cam specs for the base 502 marine from all that i have tried.

Also, do i need to do anything with the ignition box on the distributor or can i run it with the 502.

FIXX

iTrader: (2)

All gen 6 engines are roller cams,everything on your 454 except the intake and carb will work on the 502..side note make sure you pull the fuelpump off the seapump and check the oil quality,sometimes they will fill with gas and contaminate the oil..use merc hp lube when you refill it..

Install the distributor with Greece on the gears,turn the motor over by hand, pull the distributor and see if the Greece lines up with the ware marks on the distributor gear,it may be off a touch because of the load from the oil pump wanting to push the distributor gear up. use white lithium Greece,its easier to read..

getrdunn

iTrader: (7)

Both the 454/502 engines/cams should be the same. Both dist. have a roll pin that presses through the gear and shaft. The heigth of the shaft would be the same unless one or the other is a tall deck. 9.8 being std. You can easily and inexpensively change the gear if there is any signs of wear. It's a good idea to replace the gear anytime there is a cam change and after excessive hours of use. I would certainly pull the dist. and check the gear after the first couple of hours of use regardless to check for any unussual wear. With proper alignment the dist. gears will last a long time. I recently used my 454/330 dist.'s in my new 496's with Comp Cams custom grind hyd. rollers.

I wouldn't concern your self with the ign. modules right now unless your doing something trick with your new engine. Perhaps you can play with this down the road for optimum performance. I would assume you have the standard v-8/24 modules. Regardless just be sure and set your timing at total advance. Set it with your engine at around 4,000 rpm for desired setting 32-34 deg. The 500 hp engines have a different module also with a shorter curve. Having a shorter curve will help with idle and get you to full advance quicker. Some like the v-6/16 modules.

Hope this helps you out.

John

ballon78

when i shine a light down at cam gear it looks to be black.....so it that mean its a cast gear???

I read somewhere that the 454 330hp dis with ing box is a 4600 rpm rev limiter.....dont i want higher? What should i be running for rpms once im timed/ prop in for max rpms

getrdunn

iTrader: (7)

You should confirm with a MERC tech to be 100% positive regarding the gear. So you have an external ignition box and not just the module. I don't recall what they were doing in 98. My ignitions are pre 90's. Simple but effective. Not sure if you can send your box out to have the rev. limiter changed or not. Someone hear will know on that. Otherwise go buy a crane ign. box and ****can your existing one. I think they're around 250.00. Then you'll have a variety of timing curves as well as rev limiter positions.

ballon78

I just have a modual on the side of dis. thunderbolt. i did make it sound like i had a box, sorry.

I have asks a bunch of merc techs around here and non know.....plus my crate motor is a gm base 502 on a factory merc long block so they dont even know what a gm base motor is..

getrdunn

iTrader: (7)

Your going to want to run a hardened gear I would bet anything. How is the condition of the one you have. Check it over very closely for any imperfections, chips, wear patterns, etc. Otherwise replace it with one from a parts store or even a gm dealer. The ones from gm are fine to use.

Also the module mounted on your distributor. Does it have din type plug harness's?

ballon78

just saw you posted, a while back. no it doesnt look like the pic. its has an ingintion module and a knock module on it.

Is this what i should run with my new 502, since it was on my 330 454. Im woried about the rev limiter being too low, what is it set at? Should i and can I disable the knock sensor or just leave it? thanks

Panther

I'd try to see if you can shine a flashlight down into the new engine to confirm if the cam has a cast dist. gear... It will be dark in color.. If it's a billet gear on the cam it will be shiny.

If it's dark (cast), you can use a standard dist. gear.

ballon78

It is dark in color, My old distruitor came from a rollercam factorymercruiser 7.4 so i'm hopping i will be all set. what are your thoughts?