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?