Rocker box cover (clearance)

About to be disappointed but that will just add to my frustration at this point.

Does anyone make low(er) profile rocker box cover of PV lycomings?

Building a Rocket. This cowl is TIGHT. I've never gotten a hard number but the consensus here is 1/2" to 5/8" minimum clearance between the engine and cowl; not intended to start a debate. Nothing fits right on this thing and I'm trying to minimize more major fiberglass surgery.

If such RB covers exist, please let me know. Thanks

FYI, I have approx 3/8” clearance on the upper front corner of the #1 rocker box cover on my Rocket. This is with the stock cover. The stock stamped steel covers are the lowest profile I think you will find. I have a set of SDS covers and they are bit larger from having squared off corners. I had to go back to the stock cover for #1.

My RV-6 with angle-valve in the original polyester cowl has no more than 3/8" clearance to #1 cylinder rocker cover and it has never touched the cowl.

Remember that the engine does not move side-to-side, only up/down relative to the rocker boxes as the engine pivots about its crankshaft axis (the "wet-dog shake" on startup/shutdown).

hgerhardt said:

My RV-6 with angle-valve in the original polyester cowl has no more than 3/8" clearance to #1 cylinder rocker cover and it has never touched the cowl.

Remember that the engine does not move side-to-side, only up/down relative to the rocker boxes as the engine pivots about its crankshaft axis (the "wet-dog shake" on startup/shutdown).

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I can't reconcile your last sentence though I'd like it to be true, Can you get me smarter here?

I'd still have a problem but not as bad. Let me know if you would please. Thanks

Freemasm said:

I can't reconcile your last sentence though I'd like it to be true, Can you get me smarter here?

I'd still have a problem but not as bad. Let me know if you would please. Thanks

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I’m guessing that what he meant is that the rocker boxes appear to move up and down relative to the cowl because the engine (and therefor the cylinder heads) are rotating about the crankshaft.

Wet dog shake on shutdown

I've found that the "wet dog shake" on shutdown can be eliminated by not pulling the mixture to shutoff while at idle. Instead follow Lycoming Service Letter No. 192 B on Spark Plug Fouling. Instead of pulling the mixture to shutoff abruptly, I gradually lean until it quits all at once as if the ignitions had been turned off. I'm curious to know if this works for fuel injected engines as well.

https://www.lycoming.com/content/service-letter-no-l192b

9. Prior to engine shut-down the engine speed should be maintained between 1000 and 1200RPM until the operating temperatures have stabilized. At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20seconds, then reduced to 1000-1200 RPM and shut-down immediately using the mixture control.

Ironflight said:

I’m guessing that what he meant is that the rocker boxes appear to move up and down relative to the cowl because the engine (and therefor the cylinder heads) are rotating about the crankshaft.

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That's exactly what I meant. Just trying to say that the rocker covers do not get closer to the cowl than what the static installation is, and therefore you can get away with that 3/8" clearance. I actually had my cowl off today and saw that my clearance is more like 1/4" on #1 cyl.

koupster said:

I've found that the "wet dog shake" on shutdown can be eliminated by not pulling the mixture to shutoff while at idle. Instead follow Lycoming Service Letter No. 192 B on Spark Plug Fouling. Instead of pulling the mixture to shutoff abruptly, I gradually lean until it quits all at once as if the ignitions had been turned off. I'm curious to know if this works for fuel injected engines as well........

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I've found on mine that there's more wet dog shake on startup than shutdown. Maybe that's a fuel injection characteristic as some of the cylinders misfire a bit until all of the vapor bubbles are purged out of the injector lines.