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0470 running cool

A

ANGELO

Active member
Took this boat out for the first time today, the hottest I saw on the oil temp gauge was 140. That was with 3 of us on board so it was under a load. I'm pretty new to aircraft stuff, could the veratherm be removed or stuck? It seems like the cooler is getting constant flow, as soon as you start to idle it the temp drops down even lower very quickly.
 
Doesn’t hurt that the humidity is low and cool temps, check it on a mid 80’s to 90’s day. My GPU runs in the 160’s usually and below on cool nights.
 
This is what I have. Is there any way to tell exactly what it is? PXL_20230114_215343444.MP.jpgPXL_20230115_155021233.jpg
 

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No, its on the engine case around 45 degrees from the bottom. I cant remember if its at the 4/5 oclock position or the 7/8 oclock position. From the pics it will be right behind the angle bracket that holds the prop end of the engine up.
 
There is quite a bit going on here, when you tear into it, eliminate the derelict alternator bracket from the rear mount, re-plumb the cooler lines to largest,,, at least 1/2" ID for smooth flow through oil cooler.
The crossover hose between the intake logs may be omitted and plugged off.
Can shave about 25/30# by having a sheet metal oil sump built, the servo at the rear breather should be removed, oil ports plugged off, as I said, the list goes on.
 
John Fenner said:
There is quite a bit going on here, when you tear into it, eliminate the derelict alternator bracket from the rear mount, re-plumb the cooler lines to largest,,, at least 1/2" ID for smooth flow through oil cooler.
The crossover hose between the intake logs may be omitted and plugged off.
Can shave about 25/30# by having a sheet metal oil sump built, the servo at the rear breather should be removed, oil ports plugged off, as I said, the list goes on.
Click to expand...
Is this the servo to remove? What does it do? And which oil ports?
How can you tell this was a GPU conversation and not a true aircraft?

PXL_20230116_122658187.MP~2.jpg

Here's the ball and spring. I'd say that's my issue. So since it has that ball and springs there's no veratherm?PXL_20230116_183658286.jpg
 
ANGELO said:
Here's the ball and spring. I'd say that's my issue. So since it has that ball and springs there's no veratherm?
Click to expand...


That's the standard setup for cooler bypass on the GPU, Vernatherms are used on some aviation engines, including the aviation 470. The link I gave you was to the aircraft 470 folder, which still covers the cylinders. You need the GPU manuals for the crankcase:

Index of /pdf/aircraftengines/continental/gpu

You are looking at item #22 on the diagram below. It is essentially a low pressure relief valve. The concept is, when oil is cold it is thicker (higher viscosity) and therefore requires higher pressure to flow through the cross over gallery (item #14) and/or the cooler. This is not gauge pressure, it strictly responds how much pressure drop occurs through passage #14/11 and across the cam bearing. When the oil is thick, the bypass valve opens, feeding the cam and crank bearings directly. When the oil heats up, the pressure drops and the bypass closes, forcing the oil to flow through the cooler.

John is correct, you want 1/2" ID minimum hoses round trip to cooler, smaller hoses decrease the oil flow through the cooler, making for a hotter running engine. If the bypass was/is gutted, more oil would bypass the cooler and the engine would run hotter. If the bypass were plugged, all oil would always flow through the cooler and the oil would run cold.

If you want the oil to run warmer, you want a lighter spring so the bypass stays open on thinner oil. Also check the condition of the ball and seat, the more it leaks the more oil that bypasses the cooler, leading to higher oil temp.

As a hint, note that the remainder of the cam and crank bearings receive most of their oil when cold via the bypass, a good reason to warm these things up before hard use.

Finally, before doing anything, make sure your gauge is working correct. Oil temp between 180-200 F is about optimum on 50 weight. You might also want to consider multi-weight in the winter to get the oil temp up (thinner oil).

GPU Oil Diagram.jpg
 
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Slidin Gator said:
That's the standard setup for cooler bypass on the GPU, Vernatherms are used on some aviation engines, including the aviation 470. The link I gave you was to the aircraft 470 folder, which still covers the cylinders. You need the GPU manuals for the crankcase:

Index of /pdf/aircraftengines/continental/gpu

You are looking at item #22 on the diagram below. It is essentially a low pressure relief valve. The concept is, when oil is cold it is thicker (higher viscosity) and therefore requires higher pressure to flow through the cross over gallery (item #14) and/or the cooler. This is not gauge pressure, it strictly responds how much pressure drop occurs through passage #14/11 and across the cam bearing. When the oil is thick, the bypass valve opens, feeding the cam and crank bearings directly. When the oil heats up, the pressure drops and the bypass closes, forcing the oil to flow through the cooler.

John is correct, you want 1/2" ID minimum hoses round trip to cooler, smaller hoses decrease the oil flow through the cooler, making for a hotter running engine. If the bypass was/is gutted, more oil would bypass the cooler and the engine would run hotter. If the bypass were plugged, all oil would always flow through the cooler and the oil would run cold.

If you want the oil to run warmer, you want a lighter spring so the bypass stays open on thinner oil. Also check the condition of the ball and seat, the more it leaks the more oil that bypasses the cooler, leading to higher oil temp.

As a hint, note that the remainder of the cam and crank bearings receive most of their oil when cold via the bypass, a good reason to warm these things up before hard use.

Finally, before doing anything, make sure your gauge is working correct. Oil temp between 180-200 F is about optimum on 50 weight. You might also want to consider multi-weight in the winter to get the oil temp up (thinner oil).

View attachment 98000
Click to expand...
so since the springs missing its last coil, it should be bypassing longer right? unless the bypass is plugged
 
ANGELO said:
so since the springs missing its last coil, it should be bypassing longer right? unless the bypass is plugged
Click to expand...
Exactly, the engine should be running hot if the spring is the original unit but missing a turn. I noticed the spring was cut off and my assumption was that someone used a heavier spring laying around and cut it off to compensate. Imagine that, everything else is homemade, changed from factory etc...

If working properly, this type of bypass is reasonably immune from changes in ambient temperature since it actually does do a good job of measuring viscosity of the oil.

Cut another turn off the spring or get a lighter spring to bring temp up. Note the temp port on the cold side of the cooler, all good, but keep in mind that the oil going into the pan is the hottest. Water boils at 212 F, you want that oil circulating in the pan to be hot enough to vent the water out, otherwise up your oil change interval.
 
Slidin Gator said:
Exactly, the engine should be running hot if the spring is the original unit but missing a turn. I noticed the spring was cut off and my assumption was that someone used a heavier spring laying around and cut it off to compensate. Imagine that, everything else is homemade, changed from factory etc...

If working properly, this type of bypass is reasonably immune from changes in ambient temperature since it actually does do a good job of measuring viscosity of the oil.

Cut another turn off the spring or get a lighter spring to bring temp up. Note the temp port on the cold side of the cooler, all good, but keep in mind that the oil going into the pan is the hottest. Water boils at 212 F, you want that oil circulating in the pan to be hot enough to vent the water out, otherwise up your oil change interval.
Click to expand...

It wasn't cut, that last coil was inside the nut. At some point it snapped. Do you know what length that spring should be? It feels short. It doesn't feel like there's any spring pressure until the nuts almost tight. Next time I'm out I'll bring my ir temp gun and see what the coolers at.

Edit. The circle on top of the spring in my picture is the last coil.
 
ANGELO said:
It wasn't cut, that last coil was inside the nut. At some point it snapped. Do you know what length that spring should be? It feels short. It doesn't feel like there's any spring pressure until the nuts almost tight. Next time I'm out I'll bring my ir temp gun and see what the coolers at.

Edit. The circle on top of the spring in my picture is the last coil.
Click to expand...

Never put a wrench to any Clunkanental, just armchair diagnostics for me 🧐

Although no longer relevant to this situation, but to complete my understanding of things. When you first mentioned 470 and Vernatherm, I went right to the aviation manuals, ignored the part about first time airboat. Sure enough the aircraft 470 (at least the one I looked at) has a vernatherm. The logic of the vernatherm is different than the relief valve bypass. Port 31 is hot oil to cooler, 32 is return. If the Vernatherm were gutted the circuit would bypass the cooler and tend to overheat. The Vernatherm is defeated by blocking the bypass path and might include many things: epoxy, hammer, weld, ball and shims, bubble gum etc. etc.

Here is the true aviation crankcase oil diagram.

Aircraft 470 Oil Diagram.jpg


Aircraft 470 Oil Cooler Bypass.jpg
 
ANGELO said:
Is this the servo to remove? What does it do? And which oil ports?
How can you tell this was a GPU conversation and not a true aircraft?

View attachment 97996

Here's the ball and spring. I'd say that's my issue. So since it has that ball and springs there's no veratherm?View attachment 97997
Click to expand...
Spring is broken, explains the bypass and cold running temps, you can pick up a spring at ace hardware to replace it.
As the oil gets hot and thinner, the spring and ball compensate and close the crossover through the case halves and direct it through to the cooler ports.
Yes that is the servo to remove, a couple of set screws can be used to plug the oil feed and drain ports, that servo operated a breather butterfly like a throttle body in a sense.
 
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