MachinistOne

Actually went and checked my notes, started getting the old style thick casting pumps from melling back in Jul. 2010, so it's been almost two years that they have been back to the good casting. But yeah, there could always be old stock out there on someones's shelf who does low volume. Visual inspection is pretty obvious though. Packaging is exactly the same.

96capricemgr

The drive failure I have heard of are almost all overtorquing the hold down bolt. At that though they did not pop out, people heard them crack and dealt with it.

cnorton

That pretty much sums up the issues I've encountered with the pump drive/gear mechanisms. People seem to be pretty much unaware that there is a torque value assigned for the bolt.

c

pgerst

I went back to my build plan notes and one question I had was to do some research on whether sbc have the same issue; I am an old Ford small block guy and this is my first small block chevy. Do the Gen 1 sbcs have a similar failure problem? If not, interesting that the major (maybe only?) difference between the sbc and LT on the oiling system is the drive unit replacing the distributor. Possible that nylon unit flexes with increased forces of HV pump, heat and/or age and causes gear misalignment? Also you do not have the support offered by the distributor housing in the intake manifold; a good 6" plus lever arm can also help prevent flex/gear misalignment?

jeremyhurt

What is that "torque value"?

cnorton

13 ft. lbs.

bw_hunter

Pump drive at 13 lb-ft, the pump itself at 66 lb-ft.

DirtyDaveW

Anecdotal notes:

• Original pump/stub gear drive used in engine rebuild using LT4 hot cam and Melling HV pump installed 2000. In 2003, driving thru a school zone at 25mph, heard a screeching noise, looked at dash. Zero oil pressure. Pulled motor apart that night. All teeth shorn off the stub gear.
• Rebuilt motor to 383 stroker, new oil stub(duh) fitted with Crane Bronze gear, Melling HV pump. After 3000 miles, broke a valve spring, took top of motor off and found the bronze gear was down to a knife edge and soon would have failed. Went to the boards and found out that the HV pumps are renowned for accelerating gear wear.
• Replaced gear, replaced pump with new stock GM z28 pump, replaced valve springs.
• Drove another 4K miles when roller lifter came apart, taking out cam. Pulled motor, inspected bronze gear. Looked just as good as the day I put it in.
• Built turbo motor in 2008. Used bronze gear with stock pump again. Just replaced ported LT1 heads and stock intake with ported TFS heads and ported intake. Pulled gear stub out. Still looks perfect. I went ahead and replaced it with the poly gear.

As Dwayne intimates, the best deal is to get the cam manufactuer to provide the correct gear (cast gear works well with the stock stub gear). My cam was built by the 'gentleman' to whom he refers as using the wrong gear. Live and learn...

pgerst

Photo of wear on the gear; don't think that was there before the HV pump. To me, it looks like misalignment wear. Think I did the HV pump no more than 5000 miles ago, probably closer to 4K. Also not sure how i would measure the amount but there is a slight (barely perceptible in your hands) lateral movement of the shaft in the drive unit itself; also not sure if that was there or not before the HV pump.

Did some searching on the internet and did not find any failures of this type in gen 1 sbc; does anyone have any info on whether this is a problem with the gen 1 engine as well?

Assuming an HV pump works on a gen 1, seems that the drive unit could well be the problem as don't have the extra support afforded by the distributor housing. I am contemplating billet drive and composite gear as long term i do want to go with an external cooler; anyone else have any success or failure with the billet drive and composite gear with an HV pump?

shoebox

Don't see the pic...

pgerst

Picture of gear wear, sorry I have such a hard time uploading photos. I will try as link this time.
DSCF0382[1] | Flickr - Photo Sharing!

jeremyhurt

To follow up...

I want to comfirm that it was the Oil Pump drive gear that failed. I have replaced the oil pump with a standard volume oil pump, I replaced the oil pump shaft, and the oil pump drive gear. We visually inspected all the components in the bottom end. The cam and rod bearings look brand new. It appears to have new seals on both ends of the crank. The cylinder walls are smooth and don't appear to have any wear.

From what I have gathered by this forum, the drive gear probably failed because the aftermarket cam? The drive gear material may be "weaker" than the cam gear material?

Either way, I have some damage on the upper end of the engine. I had a rocker arm stud to break off in a cap. The rocker arms look like were to tight or maybe the lack of oil pressure caused some damage where the cap pressed into the rocker arm a little. In the process of cleaning the engine, I may have lost a lifter LOL. I've had terrible luck. At this time, that's all the damage we have found. I'm going to replace the rocker arm stud and lifter. Hopefully there isn't anymore damage that I cant see.

I should have the engine back in the car within the next two days.

Mystery Bird

Cool, when you're done with yours come on up and finish my new build for me.

96capricemgr

Are you talking the ball seat for the pushrod????

jeremyhurt

The polyloc has cut into the top of the rocker arm...