Truth about roller cams.... BEFORE you make the switch......

DID YOU KNOW???

  • I didn't know, thanks!!!!

    Votes: 10 55.6%

  • this is common knowledge, catch up with the times 318WR!!

    Votes: 8 44.4%
  • Total voters
    18
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Isn't this all more of an issue of billet vs cast cores?
Roller versus flat tappet has little to do with it. It's more common to run into billet roller cams, but billet FT are also out there.

This is another reason why experts suggest going with a custom cam - get it your way, it's not all just about the lobes, but also core material and final finish and heat-treat. Let the experts guide you based on what you're actually running instead of relying on one-size-fits-all answers and cams.

318willrun said:
Comp web site says this is billet. here is the cam card...

View attachment 1715477359
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Where does it say that PN is billet? The Comp website for that PN doesn't say billet for me, and photos that are supposedly of that PN don't show a billet part, but a cast core. Is it really a billet core? Seems like it's time to try to sneak a peek at it.
 
I got a Billet Hydraulic Roller for my Desoto Hemi. After researching the matching parts, got the Crane steel gear. It is relatively common knowledge that billet cams need a bronze gear, and that it does not last in a street engine. It is only recently that the Crane cams billet compatible steel gear has been around. I think you need a third part to your poll. It is specialized knowledge most people do not need to know.
 
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66fs says the gear doesn’t last.
A would not bet on a 100K life but I’d bet against the 3K life span mention.
 
rumblefish360 said:
66fs says the gear doesn’t last.
A would not bet on a 100K life but I’d bet against the 3K life span mention.
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Hmmm... Nobody told my 440-6 solid roller / bronze geared Charger it wasnt supposed to go for 10 years of street / strip driving . Some of those years it was a daily driver .
And it was in a 70 440-6 Challenger before that !
 
The gear stuff is interesting as the first roller cams in the la were on billet cores and from what I can tell used stock oil pump drives.
 
The stock hyd roller cams were billet(but not the same material you saw in most of the aftermarket), and they also used a hardened(melonized) steel gear.

An actual pic of the Comp cam in question would quickly answer whether or not it was billet.
20-745-9 is a hyd roller with the short magnum snout.
The lift listed is for 1.6RR.

There was a period of time when those shelf XR grinds were done on SADI(cast) cores.

The Crane gear works on either.
 
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PRH said:
The stock hyd roller cams were billet, and they also used a hardened(melonized) steel gear.
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Thanks for the answer, I had one reground some time ago for a 318 and the guys at oregon cam had never seen a factory billet at that point. Anyway I did some research on the drive and nobody including the dealer could say for sure if it was a different gear. There was a part number change in 1992 so some speculated it was due to increased wear with the billet but the magnums are cast. I just put the factory gear back in (that was mated to the billet roller) and it was good to go.
 
Let me clarify..... “to the best of my knowledge”.
I haven’t had any of that factory stuff in my hands in like 25 years....... but that’s how I remembered it.

My recollection is that the original Chevy factory hyd rollers were also billets, and that’s when they started using the melonized gear.
 
360duster said:
I agree with the billet stuff. Just took a look at the cam you mentioned in the other thread...comp 20-745-9, correct? Its a XR264HR-14. Comps specs say it´s a billet steel core…..but honestly i think this is plain wrong! I do have the XR286HR-10 here with me, believe me it´s a cast core. Why would a manufacturer use a more expensive material in a smaller cam? Do you happen to have a pic from your cam?

don´t want to bother you, just trying to clear something up.

Michael
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I was just about to say the same thing. Tappet vs roller shouldn't really effect the material properties of the cam gear. The core could care less what kind of lobe is ground onto it. The wear of the gear is determined by the heat treatment and more so the metal of the cam (different alloys have different heat transfer, different hardness, different elasticity characteristics). I have a cast core roller cam in my 360.

Example:
These are two, different core billet sbc camshafts I used on some lifter durability testing on a SpinTron (engine with no rotating assembly, uses an electric motor to drive valve train. Dry sump w/o distributor, so no wear on the gear, but shows how different cores have different materials properties). Same lobes, lifters springs, rpm cycles, etc. Started with a higher-quality core, usually specced for use in high stress applications. Top of the line billet core. Long story short, a piece failed and a cam journal was starved of oil. Went ahead and had a new cam made, but those cores were out of stock for a few weeks so the next level down of a core was used. At around half of the time we had on the original core, the new cam snapped.
IMG_20190325_150506.jpg

IMG_20190415_145417.jpg

So it's not tappet vs roller, but the characteristics of the core. Sort of like cast pistons vs hyperutectic or forged pistons. Oil pumps play a pretty big role in gear wear as well- a high volume pump is going to put more load on the gears than a stock pump would. Engine horsepower too- just idling around vs a 5,000 rpm jump off the line racing.

For most applications, using whatever the cam grinder recommends should suffice. Billets needs bronze, and you shouldn't cheap out on using a used gear with a new cam. Different cam grinders use different cores on different cams, and you can have different cores on cams with the same exact lobes. You can have both tappet and roller lobes ground on both cast and billet cores. Different cores within the same cam grinding company.

If you haven't seen how it's done, I recommend if you're ever in Memphis to take a tour of Comp Cams. You can see all of the different stocked cam cores, how cores are ground, how are cnc process works, the mse finishing process can be done. I'm sure every other cam company is similar, but it's more than tappet cores are cast, roller cores are billet, this gear for tappet, that for roller.
 
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I do not understand the whole hardened intermediate shaft and gear thing. Why would a aftermarket cam especially a roller cam be harder to turn the oil pump? If a factory original cam can turn the oil pump without breaking why does a aftermarket cam change that?
 
Was the valvetrain still under control when that cast core broke? What was the spring load on that failed core? What was the rpm when broke?
 
dartfreak75 said:
I do not understand the whole hardened intermediate shaft and gear thing. Why would a aftermarket cam especially a roller cam be harder to turn the oil pump? If a factory original cam can turn the oil pump without breaking why does a aftermarket cam change that?
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Go take apart an oil pump. Inside looks like this:
IMG_20200226_174828.jpg


For the shaft:
High volume pumps are bigger. More mass to turn, more volume of oil to pump. Takes more force to do that, all coming from the shaft. Think of it as a torsion bar, with added load. More twisting. You can only twist the intermediate shaft so much before it snaps and hardened shafts helps that. The gear hardness is more for the wear with the cam.

For the gear:
This link has a little info about gear material in the last section:
Distributor Gear Selection - Getting It Right Is All About The Details

Basically you want the shaft gear softer than the cam gear so you aren't wearing into the cam and compromising the cam's strength.
 
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dartfreak75 said:
I do not understand the whole hardened intermediate shaft and gear thing. Why would a aftermarket cam especially a roller cam be harder to turn the oil pump? If a factory original cam can turn the oil pump without breaking why does a aftermarket cam change that?
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Two different topics.
Hardened shaft is so the tip and shaft are stronger and are less likely to break.
Melinite hardened gear is to keep the camshaft gear from eating away at a non-compatible intermediate shaft gear, regardless of pump used.
Melinite gear supposedly does not last as long when used with high volume pump.
 
Charlesvolare said:
Go take apart an oil pump. Inside looks like this:
View attachment 1715477537
High volume pumps are bigger. More mass to turn, more volume of oil to pump. Takes more force to do that, all coming from the shaft. Think of it as a torsion bar, with added load. More twisting. You can only twist the intermediate shaft so much before it snaps and hardened shafts helps that. The gear hardness is more for the wear with the cam.

This link has a little info about gear material in the last section:
Distributor Gear Selection - Getting It Right Is All About The Details

Basically you want the shaft gear softer than the cam gear so you aren't wearing into the cam and compromising the cam's strength.
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Right! I but what does that have to do with a cam swap is what I'm asking. If im using a stock oil pump and swap to a roller cam why do I have to change the shaft and gear material? I dont understand how a cam change would effect the force on the gear and shaft
 
Bobzilla said:
Was the valvetrain still under control when that cast core broke? What was the spring load on that failed core? What was the rpm when broke?
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It was a while back, my memory isn't too clear on it, but it was lifter durability so we were trying to fail a solid roller lifter (which is pretty difficult). It had some pretty aggressive cam lobes and if I remember correctly the springs were a slightly stiffer than needed (trying to stress the lifters as much as possible). Simulated circle track laps I believe, probably 4,000 to 8,000 rpm and back over and over. Usually for durability like that we try to push it right to the limits of whatever valvetrain combo we're running. So maybe some slight float/bouncing but controlled for the most part.

And since an electric motor was driving it, it kept going after it broke. Shook like hell but kept going until we jumped up to stop it.
 
Bobzilla said:
Two different topics.
Hardened shaft is so the tip and shaft are stronger and are less likely to break.
Melinite hardened gear is to keep the camshaft gear from eating away at a non-compatible intermediate shaft gear, regardless of pump used.
Melinite gear supposedly does not last as long when used with high volume pump.
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Yes but how does changing the came compromise the Intermediate shaft?
 
Charlesvolare said:
It was a while back, my memory isn't too clear on it, but it was lifter durability so we were trying to fail a solid roller lifter (which is pretty difficult). It had some pretty aggressive cam lobes and if I remember correctly the springs were a slightly stiffer than needed (trying to stress the lifters as much as possible). Simulated circle track laps I believe, probably 4,000 to 8,000 rpm and back over and over. Usually for durability like that we try to push it right to the limits of whatever valvetrain combo we're running. So maybe some slight float/bouncing but controlled for the most part.

And since an electric motor was driving it, it kept going after it broke. Shook like hell but kept going until we jumped up to stop it.
Click to expand...

Lifters did great, ended up the link bar button was the failure point.
 
Phreakish said:
Isn't this all more of an issue of billet vs cast cores?
Roller versus flat tappet has little to do with it. It's more common to run into billet roller cams, but billet FT are also out there.

This is another reason why experts suggest going with a custom cam - get it your way, it's not all just about the lobes, but also core material and final finish and heat-treat. Let the experts guide you based on what you're actually running instead of relying on one-size-fits-all answers and cams.



Where does it say that PN is billet? The Comp website for that PN doesn't say billet for me, and photos that are supposedly of that PN don't show a billet part, but a cast core. Is it really a billet core? Seems like it's time to try to sneak a peek at it.
Click to expand...
  • It says its billet on the link you posted. Click on "specifications" and it says billet steel.
  • cam was in the van when I bought it, along with the bronze gear. No chance for me to call an expert. :)
  • again, there continues to be some that say bronze is great for years of road service, and the cam companies and many articles I've read in the last few days have said differently.
 
dartfreak75 said:
Yes but how does changing the came compromise the Intermediate shaft?
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Like using an old shaft with new cam? Using an old shaft that's already worn opens up the clearances between it and your new cam. Just better to have everything new. I don't think it's as much as compromising the intermediate shaft as much as just having everything in it's intended tolerance. Slope affects timing, can lead to more wear and failure... you wouldn't use old bearings with new rods would you? That's just what I'd imagine why
 
dartfreak75 said:
Right! I but what does that have to do with a cam swap is what I'm asking. If im using a stock oil pump and swap to a roller cam why do I have to change the shaft and gear material? I dont understand how a cam change would effect the force on the gear and shaft
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It doesn't, just depends of the material of the cam. It's not about additional force, but the wear of the different materials.
 
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