Be very careful Ned; don't just throw a new distributor gear on and go.

A few years ago I ate my distributor gear (MSD gear and Comp standard cast core hydraulic roller.)

It took 2200 miles on my car to completely destroy the gear, and the gear on the cam wasn't so hot afterwards either. Not bad, but not great.

I didn't have my oil filter bypass plugged and the debris scored all the bearings in the motor and trashed the oil pump.

What I'm saying is this... while everything is probably OK because you were running a good filter and the bypass is plugged, if it were my engine I would pull and check all the bearings.

Anyways, as said the fix is to run a genuine GM Melonized gear. It will live a long and happy life against a Comp -8 cast roller core.

The MSD gear / comp cast core cam incompatibility has been well known for several years now and unfortunately you found out about it the hard way as did I.

Also as Jody said, the -8 roller cast cores can start "tracking" the lobes; after about 400# open spring pressure or so you are playing with a ticking bomb. It may eat the lobes, it may not. The cast cores really aren't even stout enough to withstand the springs necessary to properly control the valvetrain. If you call comp and ask for spring recommendations for 2 identical cams, one on a cast core and one on a billet core they always recommend more spring pressure for the billet core cam even though both cams have the exact same lobes!

The best bet is to get the cam custom ground on a -9 billet core and then have an iron distributor gear pressed onto the cam core; comp can do this even on hydraulic roller and "street" solid roller cams. The press-on iron gear lets you run a GM melonized gear on the distributor for a very long life. That's how I do all my hydraulic roller motors now; I have 4 or 5 I've put together now on -9 cores / press on gears with GM Melonized gears and they're all running great, some have 25K+ miles on them now and the distributor gears & cam gears still look brand new.

If it was my engine, my game plan would be to pull the motor and inspect the bearings, then have the same cam reground on a -9 billet core with the press on iron gear. Put it back together and put a genuine GM Melonized gear on the distributor and it should last many, many miles.

Hey Troy
I was hoping you would drop in here. I remember talking to you about your distributor gear issues.

I specifically asked about gears before we built the motor and Comp said "no problem". I didnt know about the melonized gears..... I thought the only alternative was bronze... I knew about the billet option, but not the gear.

Yes my plan is to pull the motor and pull some bearings and basically check it top to bottom...... I dont trust the cam gear either, so there is no way I would just drop in another distributor. Not worth risking the motor.....

So can I get the gear straight from Lewis Racing ? Or do I get it from GM and ship it to him ?? Or get it honed locally ?? Troy...where do you get your gears done ???

I bought my last few direct from Mike, and I know Troy has in the past also. Maybe he has someone else he uses now, not sure.


Jody

Is this something we all should worry about, or only in specific applications? Or only a cast core?

This is so fun... what started out as a "tweaking the carb idle" day became a "pull the whole motor and replace the cam and dist gear" week... :D

I'll call Mike today and see what he has....

The one thing that still worries me.... the no oil pressure..... if the dist gear is trashed but the rotor still turns and the timing marks werent off, shouldnt I still be getting some oil pressure ???

That bugs me.....

What are your guys thoughts on the "high volume/high oil pressure" as being the cause ??

Like I said, my car has like 70 psi of oil pressure alot of the time.....

This is a specific brand & material incompatibility issue; combining a Comp cast core roller (-8 core, the standard core Comp grinds their hydraulic rollers and "Street Series" solid rollers on) with MSD's melonized distributor gear (their standard provided gear) is a nearly guaranteed failure regardless of oil pressure or other outside influences.

The solution is to get a GM Melonized gear and have it honed out to fit on the larger .500 MSD distributor shaft; the GM gear and the Comp -8 core will "play nice" together, but that doesn't fix the potential problem of the soft -8 core eating the lobes up with higher spring pressures.

Ned, Mike Lewis usually keeps a dozen or so honed GM gears in stock and can ship it out same day. The other solution is to buy the GM gear locally and have a machine shop hone it out from the GM stock ID (.491" I believe) to .500" to be a nice slip fit on the larger OD MSD distributor shaft. Any local machine shop can do it, I know Walt (Performance Machine) could for sure. All he has to do is put it on the Sunnen hone and open up the ID.

If the distributor gear is trashed, then the distributor isn't turning and thus the oil pump isn't spinning, so no oil pressure.

As far as the HV/HP pump... a new engine that has been built with proper bearing clearances has no need for an HV pump and it's just taking extra HP to bypass the unneeded oil. I do like the high pressure Z-28 pump spring though for any performance build. The HV pump does increase the load on the distributor gear and probably expedited the demise of your gear. The gear failure is a material incompatibility, but excessive load on the gear certainly speeds up the failure.

The only time I would think about using an HV pump is if the bearing clearances are really loose or if the block has piston squirters or valve spring squirters installed, and even then I would consult with those with more experience to see what their recommendation would be.

Thats the thing that bothers me....... when we turned it by hand the rotor still pointed to the #1 spark plug and the balancer mark lined up, so its not very out of synch...... when I turn the motor by hand the rotor moves, so the gears still do mesh at least some and enough that it stayed in synch with the rotor and timing mark...

Its gotta just be the gear, unless the sender took a dump at the same time.

I;ll call Mike right now.....

Talked to Mike....nice guy....not suprised the gear went south......

Also recommeded the billet cam with steel gear and the melonized dist gear..... so thats what I will be doing.....

The gear shipped to my door is $60......on its way...

There is alot of load on the geat while running from the oil pump vs. turning it by hand. That is the only way to have no oil pressure unless the pump shaft broke. Even with bad bearing you have oil pressure.

Ned, if you need another pair of hands to pull the motor or whatever, let me know. I can help you out any time the next couple of weeks.