AFAIK many of Howard's rollers are cast iron aka austempered SADI ... Howard's has billet steel also but ad says so & they cost more.

Dunno how many 305 & 350 came OE with billet steel roller and melonized dist gear ? Millions ?

 

I use billet steel custom cams because I have experienced a flatten cam lobe when the BS soft castings with flame hardened lobes first cam out. So I always order the sleeved on iron gear to use stock type dizzy gears.



https://www.onedirt.com/tech/engine/...compatibility/

 

The answer is different grades of steel. GM roller cam motors since the 80's used a technically softer grade of steel. At the shop I rebuilt some 80,000+ mile 454 BBC's. These were heavy 4X4 motors. Well anyway lots of the lobes on these original motors had roller grooves over the noses of the lobes decreasing total lift and duration.

 

but what was the GM melonized gear originally used in? they would not have developed a cam gear for aftermarket cams.

 

It appears after more research. OEM billet steel stock roller cams are harder than cast iron stock cams and aftermarket austempered. like Comp Cams. When the OE’s converted to hydraulic roller camshafts in the mid ‘80s. The cams are made from a slightly harder material, specifically 5150 steel for the GM engines, that required a more robust distributor gear. Both GM and Ford used a heat treating process called melonizing to harden the distributor gears.

Only a few companies actually make the blank cam cores. Smaller companies buy them and make their own cam lines. Anyway they realized that the steel 5150 being used in OEM hydraulic roller motors was way too soft for performance high spring pressure solid roller applications. Bronze was the original dizzy gear used as a sacrificial material (racing only). So they came up with the sleeved on iron dizzy gear idea to be compatible.

Melonized dizzy might or might not work with billet steel aftermarket cams depending on the type of steel. Why take a chance with the more expensive custom billet steel solid rollers? Just use a composite gear and be happy. I've installed composite dizzy gears in all kinds of hot rodded motors with only one failure. (probably because of 80 psi non bypass oiling system and running for extended time periods at 7500 rpm) Or order the billet cams with a sleeved on gear.

 

George, the article you quoted said that melonized gears are "compatible with all cam shafts."

Do a search. You will find all kinds of composite and bronze failures.
These gears all say "race use." Meaning ,they get checked all the time, run short runs.

You cannot find a melonized gear failure with any camshaft. Just tons of "maybe, possibly, coulda woulda shoulda." "Why take the chance."

As for the NASCAR thing, they use belt driven oil pumps, run 500 miles, and tear it down and most likely install new gears.
Frankly, I doubt they use them at all anymore.

 

Both of my vette motors have composite dizzy gears, melling high vol oil pumps, blocked off bypass. One a billet SR and the other a sleeved SR. I put a lot of miles on my Vette since the inception of the black poly gears. I do carry a spare just in case because I had trailer my vette home many years ago. probably around 2007.

I have a dizzy depth measuring gauge and set my Dizzy's correctly.

 

^^^this^^^
the onedirt article is relatively new about 5 yrs; certainly salient. Article sure does say melonized dist gear universally compatible ... At first it says Not ... But read through it deeper and it does. I have to be careful when I read an article about anything because of this very thing. At first it may support my understanding, but then later it doesn't; or vice versa.

Also, I don't KNOW but I doubt GM created/invented Melonizing (or its brethren) process for dist gears; process has been around a long time and Melonite is a trade name. And, I haven't found GM listed in the chain of trademark registrants. I don't KNOW, but do feel confident either GM or its supplier is licensed to employ the Melonite process.

Note: GM/Chev Perf has long admonished crate users to use Melonized dist gears w/ steel cam ... but GM also suggests use of their distributors having melonized gear with their other crates which have cast Iron flat tappet cams ... JMO, but that in itself supports the universal compatibility concept. When did GM first use a Melonized dist gear ? Jeez, I dunno. The process has been around at least as far back as 1976 and perhaps 1955. If I had to guess, perhaps GM began using melonized dist gear in concert with advent of its roller cam use; mid-to-late 80's is my best guess..

I don't and can't KNOW, but I too have not seen a failure between any type new cam when used with a new melonized dist gear.

NASCAR teams sure do change out hi$ parts; treating them as expendables. Some make it to retail resale. The very first time I ever heard of REM polishing was when the big teams began selling their as-new REM 9" ring & pinion sets to local short track little guys. Speaking of which, this was a great way to start the new year ... eat your heart out snowflakes ...
http://dillonspeedway.com/2019/12/01...ew-years-bash/
Grassroots teams pulled from as far as VT, PA, MO & TX ... helluva great race as always. You like howling carbed iron sbc w/ a few punches thrown to boot? There it is!
It's not so much about money or big sponsors as it is about attitude and braggin' rights.
Consolation: MAVTV / speed51 / Fox filmed; understand the weekend's races from Dillon will air just ahead of opening Nascar Daytona races.
Sure wish I could be in Tulsa to experience next week's Chili Bowl sprints. https://speed51.com/rosters-revealed...ifying-nights/

? TMI ?
https://en.wikipedia.org/wiki/Ferritic_nitrocarburizing

https://www.finishing.com/324/69.shtml

https://www.hefusa.net/salt_bath_nit...onite_qpq.html

http://www.burlingtoneng.com/melonite.html

https://www.atra-flex.com/technicalp...compressed.pdf

 

So, is this melonized gear common in all roller cam GM engines?

 

Yep, I was trying to remember what I did and your verbiage, reminded me I did the same thing. I had Lunati put a cast gear on that would work with my MSD Dizzy.

 

On those that have OE distributor & OE roller cam & OE distributor-driven oil pump ... Yes.
GM has not had those in serial production since about 2002 ...
... although the GM hi-po crates continued (e.g. ZZ6 turn key) as well as truck replacement vortec L31 sbc (think GM goodwrench pn 12681431).
SBC's replacement (LS) has no distributor nor dist gear; its oil pump driven by crank.

 

Back to post #14 ^^^^^^^^^^^^^^^^.

I guess I am confused why you would not just use a cast iron gear on a billet core as was stated way back by Tim and avoid all this back and forth?

 

.........not to get off track but how can you tell if you have a melonized gear by looking or an easy test?

 

I cannot tell by looking ... perhaps someone else can ... but a new GM melonized gear is only ~ $40.

 

so, local boneyard or car-part.com search 92 camaro 350 distributor. 20 to 60 bucks. these are the small cap HEI no advance distributors. i believe same shaft size as large cap dist. you can also use dist as an engine pre-oiler once gear is removed. nice small rotor-end shaft. chucks in 3/8 drill with no grinding smaller.

 

IIRC, later small cap HEI has smaller diameter shaft ~ .425" -.428" ... different from big cap HEI's .491"


https://www.summitracing.com/parts/a...2845/overview/

To make a primer, It's best to leave gear On shaft ... But do Grind the teeth off the gear ... the remaining lower part of gear helps capture the oil pump shaft as the the dist shaft's tang fits into pump's slot. T-shirt

 

As mentioned...I always have roller cams made with an iron gear. I use a stock iron gear with no issues. I don't want to worry about all this mess and it's cheaper than buying high $$ gears.

JIM