SBC with GM 4-71 on Cragar manifold, with Cragar drive. Running 12% over. 6 lbs of boost, revs limited to 6K Triangular plate on the face of the huffer has a hole and plug at half way level (midpoint of the drive shaft). At this level, the blower ran quiet, but when I romped on it pretty good, the oil would come out the vent (located on the top of the drive snout) and end up on the front of the motor, cowl and windshield (not good). The oil level is now down to the lower bolt hole and I can hear gear noise in the drive case. The drive still rotates smoothly by hand and the gear oil is fairly clean (it does have a little hint of metal, as I would expect to find in a new gear box). I can't have oil blowing over the car, but don't want to ruin my blower. Having never owned a blower, I'm not sure if it should have some noise from the gears. I gratefully look forward to input.
The lower bolt hole is where your oil level needs to be. (regular old 90 weight) It is also possible that your burp valve isn't seating all the way and lets fluid by at speed. If you keep your fluid at teh lower bolt hole and your burp valve is fully seating, you should be just fine. If you are seeing metal in your oil, you might be ready to open her up for a look....How long has your blower been on the street, and who built it?? -Abone.
I have a 6/71 and fill in the middle hole till it comes out of the bottom hole. You mention a vent hole. My front case is sealed but has a popoff valve. Pressure will build inside the case and if there is a path to escape, it will find it. Do you have any pics? Sounds like a cool setup.
If you look at this pic, you can see the lower bolt in relation to the sight glass.. Any oil higher than than that is too damn much. Good luck, -Abone.
bought it from a guy who bought it from the guy who rebuilt it. On the road for a week. Not daily driven, sometimes driven hard. The metal is what I am accustomed to seeing in a fresh gearbox with new gears. I'm not on high level of concern with it.
YOU OVER FILLED IT, if there are two holes in the front of the blower, the you fill it to the lower one doesn't seem like enough oil but it is, you said you have a plug in the front , look real close where the hex socket is and you will see a tiny hole drilled in there thats to relieve pressure, they did'nt always have a pressure release valve on them, the pressure relief valve is not intended to be used on the street, well at least not for long periods, makes to much pressure, but ya if it was just built you will had some metal in the oil but it should look like pearl in wet paint not pieces
It's not a pretty ride yet, but it is buckets of fun. Built it from the frame to the windshield frame. The vent is at the very top of the drive snout. It is a plastic piece pressed into the body, with a cap. No ball or seat in it.
Best description I have heard of normal metal from new gears. It is like pearl in wet paint, or paint that is stirred, not shaken. I deal with gearboxes regularly. It's normal. I expect spur gears to be noisy. I believe this bugger has helicals. What causes me concern, is that when it was overfull, there was NO noise from the drive. Now that it is at the correct level, it is noisy. Is it normal to have some gear noise from the front of the blower. In the open roadster, I can only hear it if I drive along a fence or a wall, or a car is perfectly pacing me (seldom happens). Was the too full box masking normal noise?
I don't think you overfilled it, Weiand and Dyers both fill to the middle, but it sounds like you may have bad or improperly installed seals that are letting boost pressure into the front cover. I would expect some gear oil to come out when using an open vent instead of a pressure relief valve but not the amount your'e talking about, especially with it mounted on the snout. Nice piece by the way.
I filled the case up to the plug in the middle of the triangular plate. Then moved the vent from right on the shout to up by the carb base plate using tubing. So far so good. Noise went away, and no oil on the windshield. we'll see how it does over the next few weeks.