Distributor gear question 454 to 502.
 

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.

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..

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

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

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.

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..

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?

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

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.

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?

Here is a pic of a cam, that someone took out of there 502 cratemotor...i can only assume mine is the same as wee got motors from same place just a year apart.

http://i39.photobucket.com/albums/e1...hVfBJ-MJpf.jpg

I have two of the same engines. I just ordered new cams with cast PRESSED on gear and fuel pump lobes.
These are steel camshafts that need gm part #10456413.

If you had a roller cam before you will be fine.

X2!!! IF ya had a factory hyd. roller before, your good to go,
whatever you do, don't go to the parts store and buy a
replacment-cuz I guarantee the "professionals" at pepboys
ain't gonna have a clue, and would give you the wrong part!
the gm roller gear is melonized, aftermarket"auto stores"
probably wouldn't have it anyway.

I think for insurance i would like to change my gear on my Thunderbolt ingition, I think its a V but not sure. It has a knock sensor mounted on it too. Will the GM 10456413 melonized gear fit the thundebolt V and the IV distribitors? What is the shaft size on the T-V and T-IV distrubitors?

Next...Shold i unplug the knock sensor module, and replace my ignition module so i dont have a rev limiter at 4700, its too low for the 502, coming from my old 330hp 454.

Im 99 percent sure i had a roller but dont know, the parts fieche shows a rollor cam but who knows, Merc does weird things.
here are my numbers

merc ser number OK199057
casting number 10237297

merc ser number OK199057
casting number 10237297[/QUOTE]

This gear stuff is driving me nuts!! Bought a melonized gear from GM and it wouldnt fit with out removing the washer between the gear and distributor tube.


I Just want to know 100% that THUNDERBOLT V IGNITIONS already use a hardened gear so I wont ruin my Brand New motor.

I ended up putting my old gear back on from my 1996 454 gen VI with Thunderbolt V ignition.

Im just still not sure. I have read every thread here and other site and still no FOR SURE answer.

Want to run the new 502 this weekend...

I spent 15 minutes talking to Bob Mandra yesterday about this.
Call him and he will shed some light on the topic.
I ordered two new cams from him, and he sent me two new gears to go with the cams.

You are making this way too complex.

It doesn't matter whether your 454 was a roller cam or not. Either way, in a Merc engine, it has the same distributor gear.

Just verify with 1800runsnew that the cam in your new engine has a pressed on steel gear.
If so, you are good to go and can run your distributor as is.

I have called before and they dont know much....they say its the same as what mercruiser uses....They can't give me a gm part number of the cam,or anything. Just tring to cover my bases, i have invested alot of cash and don't want to ruin the motor.

When i peak at the cam gear it look black in color compared to the shiny cam and lobes.

How do i tell the cam gear material just by looking at it?? Is there a way?

The reason Bob had to send me two new gears was because my original engine was a flat tappet, they do have different gears.
If I wanted to wait two weeks I could have a cam ground and a cast gear pressed on. There is a shortage in the cast gears since Crane when out of business.

Go look at some other sites than 1800.runs.new they advertise what gear you need. Thats the part number I posted.

I will see if I can post a pic of your cam. I have two sitting in my shop from the ones I removed. Its a steel one piece cam, the gear is not a press on.

If you call Bob Mandra he will explain all the different cores and the differences.

So if the 502 cams you pulled out of the motor are one piece steel, and my old motor was a roller cam motor right from merc, was that also a one piece cam? Are all gm cams/ merc roller cams one piece. That means my gear should work fine that i have on my stock distrubitor.

Called Bob today , he said that if my old motor was a roller motor than im fine........

Its just So many people are telling me different things that i dont know what to do. Seems to me that my stock merc Thunderbolt V gear should work fine if it worked on my gen 6 454 330hp.......

1BIGJIM see if you can get some close up picks of the gear on the cams. Mine looked black in color...was your like that?

The man has answered.

The gear is black, a cast gear is black, that is one of the topics Bob was trying to explain to me. Sometime he gets to talking and and it goes over my head.

Sleep well tonight:drink:

If I have time I will put to different ones side by side and post a pic.

I thought you said that the 502 cam was a one piece cam, so the gear on mine and your cam is black in color? How is the cam steel and the gear cast? Basicly bob told me that if my cam has a pressed on cast gear that has been hardened then i also need a hardened gear in the distrib.

You can clearly see the difference between the two cams.
Like Griff said earlier you are making something out of nothing.

I to was concerned like yourself, but I have two new engines at risk and will end up in divorce court if I mess it up :drink:

So is the GM Base 502 motor have a one piece billet steel roller cam, and the Mercruiser 502 mag have a different two piece cam with cast gear? Or are they the exctly the same.

Anyone have the part numbers for the gm one in the base 502.

So the 454/502 Merc #431-850478 cam is identical, a one piece cam just like the GM# 12551622 that we have in the GM Base 502 motor. i was under the impression the the merc and gm base cams are simular but not exctly the same. As long as both cams have same exct one piece gear on the cams i will run the merc gear #43-818807 Either way i need a new cam gear, cuz my stock one had a slight amount of wear, and when i installed the Gm MELONIZED ON THE mERC distributor there was no end play (vertical) the gm melonized gear seem to be a hair longer and distributor wont turn. So I was just going to buy a new Mercruiser gear as long as they are melonized too.

I know im going crazy over this, just want to fully undersatnd it. lots of grey area and 100 of post not confirming anything all over the internet.

Thanks for having patients with me!! :)

In case someone digs this up in the future.:eek:

Both cams are one piece.

one is a billet steel Roller the other Cast Steel flat tappet.

You can press a cast gear onto a billet steel cam to retain the original distributer gear used on a flat tappet cam.

No i know the 502 base motor has a billiet one piece cam, but i was wondering if a 454 mag or 502 mercruiser has the same one piece cam or if it is the same profile but has a pressed on gear and a two piece.

Someone must have pulled gen 6 mag 454/502 out of a stock merc motor..

Just a side note for anyone reading this. DO NOT put a dist. gear that has been run on one cam onto another cam, even if the cam is new. You are asking for trouble. Go ahead, ask me how I know. Once a gear has been run on a cam, it should not be used on another cam. Replace the gear with a new one. You can keep the gear with the old cam so if the cam ever gets reused, then you can reuse the dist gear.
In your case Ballon, you need gear # 10456413.
Eddie

Learn something new every day, even at 48 years young.:drink:

I would be scared to count how many cams I have changed and ran the same gear. I am surprised Bob M. never mentioned it, because that is the reason I wanted have always ordered cast gears to use the same gear on my old distr...

Eddie I have the GM Melonized gear, and tried to install it, but its was so tight the distributor wouldn't even turn. If I remove the stock shim then its good, but I cant run the distributor with out that shim.....What should the shaft end play be set at for a minimum. I ended up puting the stock gear back on and orderd a brand new merc gear to put on this weekend. How come my old motor which was a 330hp 454 with a roller cam can run the stock Thunderbolt V merc gear and the 502 gm base can't. Is the 330hp cam non magnum roller cam not a one piece billet like the 502 cam.??

Trust me i wish i could just toss on the GM gear and be done already!! :)

They do take the same gear. I sent you a pm on how to fix the endplay.
Eddie

Me too. I have never replaced a dist gear with a cam swap unless it showed some significant wear. Makes sense though, since everything develops wear patterns.

Obviously, a used gear possibly can live on a new cam. Plenty people have done it. However, I can not tell you how many I have seen them wipe out the gear in 2 hours or less. It has happened to me as well in the past. I could maybe attribute others to someone doing something wrong, but I know I didn't do anything wrong. I loaded them up with the same Moly lube I always use on new gears, and they still got wiped out. Learned it the hard way. You may be able to get away with it, but I will never take that chance again. It is not worth having to take an engine apart over a $50 gear.
Eddie