Hi there. I'm a long time lurker and now a first time poster. Here is my question. I've got a recently installed 383 with a comp cam solid roller cam (with a standard iron oil pump drive gear). I've also got a high volume high pressure pump (I know, but I've got a canton road race pan). Anyway, everything has been fine for the last 3-4k miles until I pulled the car out of the garage last night. Oil pressure was normal and then the "Check Gauges" light began to flash and the oil pressure went nearly to zero, and then to zero. I pulled the intake off today as I had a feeling that there might be a problem with the oil pump drive (I didn't replace it during the rebuild). Sure enough, there was SEVERE wear on the remaining teeth and a whole bunch were missing. Fortunately, the cam gear appears ok. When I bought the cam, I asked what they recomended for an oil pump gear and they said a Mealanized one. The problem is that this stupid drive assy does not use the standard .491" shaft diameter that all SBC's use so the gear that I bought from Summit wouldn't work. That's why I didn't replace it at rebuild time. Well now I've got to do something. Are there any alternatives to the stock drive assy gear? I checked the dealer prices for the drive assy, and they go for $37-$65. This is silly as I only need the gear itself. Are there any sources for just the gear and if so a Mealanized one? Sorry for being long winded, but I guess that's what happens when you lurk as long as I have!
Thanks in advance!
Scott

 

Nope.

You will need a cam that is a billet roller type just like the regular LT-1.
I do have a gear assembley I'd let go for like $10 if you wanted another one. I'm sure it will just chew up like the last though.

-Shannon

 

Here's the thing. This particular drive assy has approx 45k miles on it (it's the original one) and has seen approx 5 different cams in it's life all of which were CC with the iron drive gear and the driven gear looked good when installed in the 383. I suspect that the added load of the HV oil pump and normal wear caused the death. Once it wears through the hardened layer it quickly disintegrates. Is the drive assy you have new?

 

Nope, mines used. Prolly about 60k on it.
I've been runnign a HV pump for about 3 years now in all of my engines and my customers with no issues like you describe.

Do you have the part # for your cam ?

-Shannon

 

Yup. The cam is an off the shelf grind XE mechanical roller that was custom ordered on an LT1 core (so it has the long dowel pin and the drilled hole in the center). It's catalog part number is 12-771-8, but on an LT1 core so I think it would then be a 07-771-8. After doing some research just now I suspect that the factory driven gear must be a melonized iron gear to be compatible with the steel core of the factory cam. I believe that this type of driven gear is also compatible with a standard drive gear. You know one of things where you can use a melonized gear on either type but you cannot use a standard iron gear on the steel cam, or something like that. Either way, it appears that the cam gear is still ok. If I remember correctly the shaft diameter is .470" and no google search will turn up a result for anything. As far as your customers having no problems, like I said neither did I through five cam swaps until now. Maybe it was already worn partially through the hardening layer and the HV pump finished the job.
Thanks for the help, by the way!

 

You can put another stock drive in and it WILL eat it up.Your cam material and your drive material are not compatable. If you can't find a drive gear you will have to change the cam. Call MSD and see if they will sell you a bronze gear without the shaft hole or maybe make you one the right size. Comp cams and Crower sell them too.
Those drives will go 200,000 miles and not show much wear.
If you keep chewing up gears you will have to tear it down and rebuild from the metal,and just an oil change won't do it.

 

Yeah, I'm quite worried about the metal as well. From what I understand bronze gears were developed for steel cores. This cam is an iron core just like most aftermarket street rollers and as such "should" be compatable with a stock distributor gear (or oil pump gear in our case). This is Comp Cams statement too. And like I mentioned earlier, it caused no problems in the old 350 with the same iron cam cores and the standard volume pump. I'm willing to bet that the majority of aftermarket cams installed in LT1's are NOT steel cores like the factory item is. So far NONE of my aftermarket ones have been and one of them was actually a TPIS ZZ9 (what a joke that one was )
Thanks again for the help.

 

ALL the cams I install are custom billet whether mech or hyd and haven't had any problems. I can't get a LT-1 with any mods to run right with the off the shelf stuff.(when I say right,I mean like I think they should with its given mods)

 

Completely on a side note, what are the advantages of a billet roller vs the newer hardened iron cores? If I remember correctly, in the begining the metalurgy wasn't there yet to make an iron core strong enough for roller duty, so they were made of billet steel. And it was there detriment that they were because it was rough on normal dist gears, thus bronze gears were born. Relatively recently it's been feasable to manufacture out of hardened cast iron, providing comprable strength, but with the compatibility with common and durable regular dist gears. That's just what I heard.

 

Side note also. COnverting my wifes car to Carbed LT-1 we also converted to flat tappet race cams. This required us to use a bronze gear.

I'm wagering you have a problem somewhere else. Maybe the clearance wasn't anough or something similar ?

-Shannon

 

Well, we will see what happens. I ordered a replacement drive assembly from Dal (awesome experience, btw) and it should be here by the weekend. It's a shame it's so darn inaccessable, otherwise I'd be able to periodically check it. Thanks again for everyones advice!