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Discussion Starter #1
I finally put some time on my 6-71 blower and i'm having some issues with the gear case on it. Just cruising around i'm getting tremendous pressure in the case its pushing oil out of the snout bolt holes and even through the pores in the aluminum on the snout. Any ideas on what could cause this problem? I'm using 80-90wt gear oil and filled it to the snout hole that is in the aprox 7 o'clock position. It doesn't have a fill sight glass or bolt and no pressure relief. Also this blower cam with the boat and the guy before me never ran it, so how would i tell if it was setup for alchool. cause the cases get hot to the touch while running it. It has strips on the tips of the lobes. In the photo you can see it pushed out the tread sealnt on the snout bolts. along with some gear oil.
 

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I finally put some time on my 6-71 blower and i'm having some issues with the gear case on it. Just cruising around i'm getting tremendous pressure in the case its pushing oil out of the snout bolt holes and even through the pores in the aluminum on the snout. Any ideas on what could cause this problem? I'm using 80-90wt gear oil and filled it to the snout hole that is in the aprox 7 o'clock position. It doesn't have a fill sight glass or bolt and no pressure relief. Also this blower cam with the boat and the guy before me never ran it, so how would i tell if it was setup for alchool. cause the cases get hot to the touch while running it. It has strips on the tips of the lobes. In the photo you can see it pushed out the tread sealnt on the snout bolts. along with some gear oil.
Keep in mind that the gear case is under the same pressure as the manifold. The seals are not intended to stop pressure from entering the case, but to keep oil from entering the blower. The bolts need to be sealed well enough to keep the oil from being pushed out. As for the oil coming thru the pores in the alum, that rediculous. Does that mean the fuel is being pushed thru the pores in the blower, or thru the bottom of the manifld? If it is infact coming right thru the snout, I would question the quality of the snout casting. There are blow thru carb deals running 20+ psi and they don't push fuel right thru the float bowl casting.

The assembly is good well past 50psi. I guarantee you are no where near that.
As for the heat on the case, they will run warm, specially at low RPM and low air/fuel flow. Thats the devil in the roots. If the strips are white, its most likely a gas blower. It will loosen up and will run a little cooler when it has run awhile. In the mean tme, try not to let it idle too long as it may over heat the strips.



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Yes the oil was coming through the pores they were almost worm holes in the casting i took an air blower with a ruber tip on the inside with soap and water on the outside and yup got bubbles.. so i sealed those with a smear of silicon on the inside. i understand about same pressure as the manifold but its building this pressure under a vacuum i only got 4 lbs of boost for about 3 seconds on the whole run all the time i was cruising and the engine was under a vacuum.
 

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Yes the oil was coming through the pores they were almost worm holes in the casting i took an air blower with a ruber tip on the inside with soap and water on the outside and yup got bubbles.. so i sealed those with a smear of silicon on the inside. i understand about same pressure as the manifold but its building this pressure under a vacuum i only got 4 lbs of boost for about 3 seconds on the whole run all the time i was cruising and the engine was under a vacuum.
Wow, love to know who made that snout.
Even though you only hit 4 lbs once, that pressure stays in the gear case till it leaks out or is released thru a pressure relief valve. I have had pressure remain in the gear case for days. Its a one way deal. Just because the engine went back to a vac condition, the pressure in the case remains. Otherwise, if the pressure was allowed out under vac, the oil would go with it. The seals job is to hold the oil, and any pressure that is the case.

If you did not over fill the case, and 7 o clock is fine, so its not that, I assure you, the assembly is more than capable of withstanding whatever pressure you are going to throw at it.



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shaft seals

The seals should be installed so that boost pressure loads the seal. They may be installed backwards so that boost pressure blows by them and pressurized the gear case. Then case pressure loads the seals holding the pressure inside when the engine is idling.
 

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The seals should be installed so that boost pressure loads the seal. They may be installed backwards so that boost pressure blows by them and pressurized the gear case. Then case pressure loads the seals holding the pressure inside when the engine is idling.

I knew that name looked fimilar.... I just ordered your 5K HP book
 

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The seals should be installed so that boost pressure loads the seal. They may be installed backwards so that boost pressure blows by them and pressurized the gear case. Then case pressure loads the seals holding the pressure inside when the engine is idling.
Hi Bob, it great to have you on this site. Your a wealth of knowledge. I also have you book "5,000HP On Methanol"
 

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Discussion Starter #11
The seals should be installed so that boost pressure loads the seal. They may be installed backwards so that boost pressure blows by them and pressurized the gear case. Then case pressure loads the seals holding the pressure inside when the engine is idling.
Very well could be the problem then, i'm going to pull it apart this week to take a look.
Thanks for the help.
 
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