1BIGJIM

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

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

ballon78

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.

1BIGJIM

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

ballon78

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.

ballon78

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!!

1BIGJIM

In case someone digs this up in the future.

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.

ballon78

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..

Young Performance

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

1BIGJIM

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

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...

ballon78

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!!