IO-390 Saf-Air location?

I used the Saf-Air oil drain plug on my RV-8's IO-360 and bought one with the intention of installing it on the RV-14A's IO-390. However...

The -390 doesn?t have a single, obvious plug on the bottom of the crankcase, but two plugs (yellow arrows on attached photo) at an equal height - neither of which is anywhere near the lowest point of the system. The red arrow indicates the sniffle valve (covered in this image) location.

So?where to place the oil drain valve?

Most or at least IO360 also have two plugs.

If you are going with VANs exhaust, you will need to do it on the pilot side due to access. Also, just in case you are not aware of it, VANs has a modification for the co-pilot side heat box which will cover the opening. It is an easy change to make but sooner the better as you still have plenty of space/access.

Nice looking engine.

Bavafa said:

Most or at least IO360 also have two plugs.

Click to expand...

This point must have escaped me after all the intervening years. Thanks for the reminder!

If you are going with VANs exhaust, you will need to do it on the pilot side due to access.

Click to expand...

I am going with the stock exhaust and will install the oil plug on the pilot's side. It seems as though it won't completely drain the oil, not being at the lowest point, but it is what it is.

Also, just in case you are not aware of it, VANs has a modification for the co-pilot side heat box which will cover the opening. It is an easy change to make but sooner the better as you still have plenty of space/access.

Click to expand...

OK, what am I missing? Why would someone want to cover one of the heat boxes? Does the uncovered heat box flow much heat to the cockpit even when closed?

Nice looking engine.

Click to expand...

Thanks! It's coming along...

Silicone the gaps at the inboard end of the inter-cylinder baffle, now, before you hang the exhaust.

Form a radius bend on the ends of the inter-cylinder baffle under each cylinder head, and you can wire the wraps together under each individual cylinder, rather than running a tie bar from the front to the back cylinder.

You'll thank me later

kbalch said:

This point must have escaped me after all the intervening years. Thanks for the reminder!



I am going with the stock exhaust and will install the oil plug on the pilot's side. It seems as though it won't completely drain the oil, not being at the lowest point, but it is what it is.


Thanks! It's coming along...

Click to expand...

There is a location for the oil drain on the lower back of the IO-390. It will drain better. That is where the Vans demo is drained.

kbalch said:

I used the Saf-Air oil drain plug on my RV-8's IO-360 and bought one with the intention of installing it on the RV-14A's IO-390. However...

The -390 doesn?t have a single, obvious plug on the bottom of the crankcase, but two plugs (yellow arrows on attached photo) at an equal height - neither of which is anywhere near the lowest point of the system. The red arrow indicates the sniffle valve (covered in this image) location.

So?where to place the oil drain valve?

Click to expand...

Those drains are closer to the low point than you might think. Remember that the intake manifold/plenum is under the sump, so most all of that extra depth you see in the casting is the intake manifold.

With a taildragger, you do have to put the tail up on a stand to get the fuselage level so those drains will drain completely. The rear plug, pointed out by M McGraw, will drain better for taildraggers, but is not as convenient if you use a quick-drain. I suppose a quick-drain with a hose on it would work fine, but probably drain slower than a quick-drain in the forward location, pointing downward straight into a bucket. That is what I do. I have a stool that is just the right height to level the fuselage when I put the tailwheel on the stool.

Either of the two you marked is fine - I chose the one on the left because the other side was closer to my FM-150 throttle and mixture cables, the one on the left was clear: I think with standard mixture/throttle cable routing the right side may work better.

They are on the bottom of the oil sump as someone else pointed out - the lowest point on bottom of engine is for induction air. (sniffle valve drains induction)

Last photo in this post shows the drain as I placed it: https://turnerb14a.blogspot.com/2019/01/firewall-forward-work-starter-switch.html

Thanks, guys.

While the rear-mounted position looks like a good location for a tailwheel airplane, one of the downward-pointing drains makes more sense to me for a nosewheel airplane's quick-drain.

I'll select one of my "yellow arrow" locations once I've installed a few more FWF components and I can confirm which offers the better clearance from exhaust, wires, cables, etc.

Mine made the most sense on the pilot front side after getting everything installed.