What is this spacer for?

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mondtster

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mondtster
Hey guys, I'm working on a new to me D model Aztec with IO-540-C4B5 engines. The plane is in the shop for an annual right now and I noticed this spacer between the fuel injection servo and the oil sump. What is interesting is that one engine has the spacer and the other one doesn't, which is why I'm trying to figure out why someone added it in there.

Looking at an IPC, Lycoming does appear to specify a spacer on some engine applications. It does not appear that the C4B5 is supposed to have one so my thought is to remove it. However, I'd like to know why Lycoming used these on some engines. Does anyone know?

Both engines seem to run the same, so whatever it was intended to do doesn't seem to affect engine performance.
 

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My guess is it resists heat transfer from the sump to the injector.... :dunno:
 
Since it's non metallic, I would suspect it's a heat insulator. I would leave it in place.
 
Maybe for some type of clearance issues to keep linkages and what not straight?
 
Heat may be a factor to consider in why someone installed this spacer on this Aztec. Or it may have a positive contribution anyway. I hadn't considered until now that the left engine hot starts much easier than the right engine, and the left engine is the one with this spacer installed on it.

The biggest problems with leaving the spacer installed is that it isn't supposed to be there and it moves the air box down far enough to rub on the cowl. The air box has been repaired at least once in the past and I had to repair the cowl because of it.
 
mondtster said:
Heat may be a factor to consider in why someone installed this spacer on this Aztec. Or it may have a positive contribution anyway. I hadn't considered until now that the left engine hot starts much easier than the right engine, and the left engine is the one with this spacer installed on it.

The biggest problems with leaving the spacer installed is that it isn't supposed to be there and it moves the air box down far enough to rub on the cowl. The air box has been repaired at least once in the past and I had to repair the cowl because of it.
Click to expand...

There is that..... It always amazes me on how tight they run clearances in certified planes...
 
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