Crankcase Vacuum Kit Complete

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Part# 05-12429


Anti-Splat-Aero is very proud to offer this complete, very reliable crankcase vacuum valve kit. Included are the 321 stainless steel saddle mount fitting, mounting clamps, vacuum valve assembly and a complete safety by-pass with a .25 psi internal pop-off valve. This will put the finishing touch on your oil separator installation or breather system.

We have had many requests for these items to enhance the installation and realize that it may be very difficult for many people to obtain these items locally or to accomplish the task of welding it into the exhaust. Now all that is required to install this performance system is to drill a 5/8 clearance hole and clamp it on. Full installation and maintenance instructions will be included. This one way vacuum check valve accomplishes a number of things, (all being good) and greatly enhances performance of your aircraft. I will attempt to touch on some of the benefits here. This assembly, when fitted to your engine will create a vacuum in the crankcase of 5 or 6 inches when in operation. It accomplishes this via two separate actions, #1 exhaust flow over the bias cut tube, and # 2 the pumping action of the engine crankcase volume changing with rotation. The one way valve allows the crankcase to exhale only, and this action creates a low pressure in the crankcase. The engine is sealed and the only air path in is through the piston ring end gap or the valve guides. This usually cuts oil consumption in half, or stops it all together, as the stated areas are where the losses occur.

Your engine will virtually stop all leaks and seeping when in service, due to the vacuum inside. This system stops any possibility of freezing up the breather tube in cold climates, as no moisture laden air is present in the engine and none can be inhaled through the overboard draft tube. The rarefied air and low pressure in the crankcase has a very dramatic effect on windage and oil in suspension, thus freeing up a little power and adding some efficiency. This will also greatly lower the boiling point of any moisture that finds its way into the engine. Any oil temperature over 160 degrees will get rid of all the moisture in turn the acids. Any lowering of pressure on the underside of the pistons is exactly the same as adding cylinder pressure on top. This results in a very noticeable power increase (on the average 180 HP engine, 3 to 5 HP). We hear this over and over with reports of higher static RPM, better climb and acceleration, lower fuel burn etc.

The belly of your airplane will stay immaculately clean as anything that exits the separator or breather line will be consumed in the exhaust stream.
California Prop 65 Warning Symbol

WARNING: The product may contain and/or expose you to a chemical(s) or substance(s) which are known to the State of California to cause cancer and/or birth defects or other reproductive harm.

In The Box

  • 321 stainless steel saddle mount fitting
  • Mounting clamps
  • Vacuum valve assembly
  • Complete safety by-pass with a .25 psi internal pop-off valve.
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Good quality kit. I actually bought this as an experiment on an old MG (automobile) rather than an aircraft application. The only souce of crankcase ventilation on these old cars is a draft tube off the tap cover that creates very little, if any, vacuum and as a result oil leaks on MGs are considered normal. So far this kit appears to do what it claims, producing 5 to 6 inch WC vacuum from the small draft tube inserted to the exhaust. It has just been installed on not enough run time to fully evaluate the results but so far it looks good.

Scott M
March 1, 2020

Kit looks great, yet to install so can’t offer an opinion on the performance benefits

Brian D
December 4, 2019

I have purposely waited awhile to write this review in order to be able to be objective. I can say with confidence that the manufacturer’s claims are true. The belly of my plane is much cleaner and the fuel burn has dropped about one gallon per hour since I installed this system. I would recommend that the operator be sure to simply follow manufacturer’s directions, which are quite simple.

David R
December 15, 2018

Kit was not complete. Saddle mont assembly & evacuation tube was not in the kit.

Jan S Verified Purchase


June 6, 2021


Please note, Pilotshop's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Pilotshop assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Does this crankcase vacuum kit also require an oil/air separator be installed?

No. An oil/air separator is not required to be installed.

Q: Is this crankcase vacuum kit FAA Approved?

No, this is not FAA approved.

Q: where does it mount tailpipe or header pipe ahead of muffler? Will it work with dual exhaust? Is hose included?

The preferred mounting location is ahead of the muffler it will function behind the muffler however the could be coking problems with that type of installation. Yes works with any type of exhaust system. The only hose it comes with is for the bypass.

Q: What Size is the hose?

This is a 5/8" hose.

Q: What sort of cleaning or maintenance does this Crankcase vacuum system require?

We recommend cleaning the saddle mount every oil change or 50 hrs of operation. We have added the instructions to the Documents tab of this web page for your reference.

Q: What diameter exhaust pipe does this fit?

The saddle mount will work on 1-5/8" to 2-1/2" exhaust pipe.

Q: If this is not FAA approved, what can it be installed on legally?

This can be used on experimental and homebuilt aircraft.

Q: Can this be installed in a light sport aircraft?

This item is not FAA Approved. Please contact your A&P to discuss if this item can be legally installed in your LSA.

Q: Your first two Q&As are confusing in details. Does this item require a ail/oil seperator to be installed? Can it be installed without a seperator all together?

You can install this product without a separator but is best with one, per the manufacturer.

Q: Do you need the separator with the vacuum kit of not? The only pdf shows both.

Per the manufacturer: You can install this product without a separator but is best with one. We cannot see a reason to not want one.