cam/lifter survival vs distributor gear survival

[montez27]

OK, I just want to ask how ZDDP in earlier SG, SH and such oils(or break-in additives) helped flat tappet lifers survive 100+lbs up to 300+lbs of pressure, thousands of miles without destroying the cam or lifters in short order??
But that same ZDDP can't seem to help a regular cast distributor gear survive on a steel roller cam.

I have done quite a bit of research on gears and cams and I will most likely get a Lunati everwear gear for my distributor. I have used melonized gears but that gear went away with an old distributor I use to use.
I have seen pics of very worn gears when cast was used on billet. I understand why it happens.
I was just wondering why the ZDDP doesn't work to keep these gears from being destroyed like it does for the cam and lifters.

 

[Shannow]

Given that the gears are 90 degrees, the mode of action is more sliding than rolling (like parallel shafts are).

If you had a stand alone gearset with such an arrangement, you'd be heading towards more EP type additives than typical ZDDP AW additives.

 

[heyu]

You say -- that same ZDDP can't seem to help a regular cast distributor gear survive on a steel roller cam.

Overall your supposed to use a bronze gear on a roller

In all my years i have not had or seen this happen

Kinda sounds like you have a defective intake that is drilled offset or your block has alot of coreshift ( cam off center in block ) which is common but with a intake doing the same it's going to tear something up

 

[montez27]

OK. Lifters slide plus rotate as they have a slight crown (when new).
In the case of the SBC, the cam is always forced back, towards the rear of the engine, against the distributor while rotating the gear and spinning the rotor as well as the oil pump.
I wonder what the pressure is between those cam and distributor gear/teeth?
Doesn't ZDDP adhere to metal by means of heat and pressure?

 

[heyu]

True , But if the cam gear is properly shimmed correctly there is no forced back pressure, All cams have different shim specs , If you have something misaligned -- no additive is going to protect it from getting chewed up

 

[DoubleWasp]

Agrees. Sounds like a clearance or metallurgical issue to me.

 

[The_Eric]

Originally Posted By: heyu

You say -- that same ZDDP can't seem to help a regular cast distributor gear survive on a steel roller cam.

Overall your supposed to use a bronze gear on a roller

In all my years i have not had or seen this happen

Kinda sounds like you have a defective intake that is drilled offset or your block has alot of coreshift ( cam off center in block ) which is common but with a intake doing the same it's going to tear something up




That's assuming you're running a steel cam/gear. Some roller cams are cast- like the Comp Cams hydraulic rollers and some have a cast gear put on the camshaft for distributor gear compatibility.

Originally Posted By: DoubleWasp
Agrees. Sounds like a clearance or metallurgical issue to me.


I think you've got it with the comment on metallurgical issues. From what I've seen with aftermarket distributor drive gears, they are JUNK! This doesn't include the latest, greatest gears, as I have no experience with them.

I think the real ticket is to get the GM melonized gear again. If you are running an aftermarket distributor with a .500" shaft, then you'll have to have the GM gear reamed out to fit as they're .490".

 

[SwampSurvivor]

Once the lobes harden ...

 

[punisher]

One of the first rules you learn going to a steel billet roller cam- Never ever run a cast distributor gear with it. You already know that though.

Truth be told I don't think ZDDP is the best material for EP sliding friction. Couple that with insufficient oiling, and high volume oil pumps loading the driven gear, no wonder they die. When I order rollers I specify a cast drive gear if available. If not I keep a few spare bronze gears handy. Supposedly there are some new composite gears that work better with billets but don't have any experience with them.

 

[TFB1]

Originally Posted By: punisher
One of the first rules you learn going to a steel billet roller cam- Never ever run a cast distributor gear with it. You already know that though.

THIS^^^^

I've seen cast dist gears worn away by billet cams(will take approx 10K mi in Ford Small blocks)... YES it will happen EVERY time it's done and no amount of so called alignment, shimming, etc will fix it... There is a good reason OEM uses steel gear distributors...

 

[montez27]

Excellent replies, all. My cam is the ZZ4 gm cam. Steel yes but I don't think billet.
Yes GM specifies use of a melonized gear and I will most likely use the Lunati everwear gear.
I use a standard volume oil pump as I didn't build my engine loose.
I have used several distributors. The MSD HEI I had worked very well and had a melonized gear but the intake I am now running requires a small body distributor so I had an MSD RTR(readt to run)(ready to quit) and it quit on me. Sent to MSD and had it repaired. I asked MSD if the gear was melonized and the answer was yes. But how to be 100% sure?? When the MSD was being repaired I had a pertronix RTR ignitor 3. I emailed pertronix and asked about melonized. The answer on email, yes. Spoke to a real person at pertronix and answer was no.
So yes, lots of confusion.
Thanks again for the expertise. I will order up a lunati gear and hope all stays good.