Help!!! Crankshaft seal keep blowing

Mr.Clark

New member
Hello all I have vented engine via : New block with billet sidecover & valve cover four ports In total mild build billet rod +.20 , billet flywheel , 292 cam , 27/25 milled 50 head, 24mm flat slide, F&B header, Ect.
Starts runs great blows case seals on either the Pto shaft side or the flywheel side over and over I’ve changed both same thing I looked around no info on this issue I need help!
 
Use 3/8 vent instead of 1/4. Make sure to use a pcv valve because it doesn't really do you any good if you dont.
 
Clean the hole and seal with acetone then coat the seal and hole with Permatex black adhesive sealant and install. Let it cure over night.
 
On the crankcase. With just an open vent it will suck air back inside. A pcv valve will create a vacuum inside the crank case and helps rings seal.
A common mistake is using a simple brass or aluminum fitting without a check valve. This means air is pushed out, but also air can be sucked back in, defeating the purpose of a vent. In built engines, it is not enough to vent crankcase pressure, but also control crankcase pressure.
 
On the crankcase. With just an open vent it will suck air back inside. A pcv valve will create a vacuum inside the crank case and helps rings seal.
A common mistake is using a simple brass or aluminum fitting without a check valve. This means air is pushed out, but also air can be sucked back in, defeating the purpose of a vent. In built engines, it is not enough to vent crankcase pressure, but also control crankcase pressure.
we vented limiteds with two holes on the side cover and one on the valve spring cover . common practice. all the tubes just went to the oil catch can 9700 rpm never an issue. a 600 rotax has nothing but a little k&n filter on the top of the crankcases no valve just to atmosphere common practice never an issue
 
There is plenty of info out there why you should use a PCV valve but its not completely necessary. They are used in most automotive engines and I'm guessing they have a good reason.
Why do you want to fill the crankcase full of air on the up stroke if you don't have to? It then has to push more out.
With two holes in the sidecover it's probably less of an issue.
Paul at Paul's karts talks about this and sells the valves as well.
 
One thing to consider . The air thats pulled in . It carries dirt and debris into the crankcase . Pvc vale or not , it needs a filter .
 
On the crankcase. With just an open vent it will suck air back inside. A pcv valve will create a vacuum inside the crank case and helps rings seal.
A common mistake is using a simple brass or aluminum fitting without a check valve. This means air is pushed out, but also air can be sucked back in, defeating the purpose of a vent. In built engines, it is not enough to vent crankcase pressure, but also control crankcase pressure.
So Coby You put it so the crankcase can vent but not suck in.? so you put the end you can blow through to the valve cover.? Am I correct.? Thanks
 
Yep. Goes from the sidecover and vents to the valve cover. Just make sure your valve cover has a separate vent going out, this can be just a regular fitting and not a pcv. If you use a 3/8 pcv, use a 3/8 on the valve cover and send it to a catch can if you want.
 
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