New optional plans OP-58 - Lower cowl louvers for RV-6/7/9

[rv6n6r]

This will probably take it off on a tangent but what CHTs are we shooting for? For 12 years my -6 (O-360 normally aspirated) virtually never got above 400 then I switched engine monitor systems and all of a sudden they're going above 420 on climbout on a warm day! Obviously that's some difference in the probes not the temps themselves but I'm confident the new system is accurate.

Anyway is it bad to get into the 420s for the 5 minutes or so it takes to get to altitude? In cruse I'm always below 400, and by "the book" (Lycoming's), that's no problem. But I've read some articles that say you should never let it get above 400 more than momentarily. What's the common wisdom?

And Scott, you can expect me to drop by sometime and have you show me where I can improve my baffling!

[WingsOnWheels]

On this same topic, I see a lot of variations in CHT issues from one build to the next. While in many cases it may be baffling, tuning, or exhaust configuration, I am curious if there are cowl variations impacting this as well.

For example, my CHTs are running really high. Now, the engine is still in break-in and it is summer, so that doesn't help, but I can barely get to pattern altitude under and stay under 450. I have a cooling plenum and have gone through it multiple times and made sure every leak is plugged.

When I fitted my cowl and airbox (vertical induction) I noticed that the clearance from the airbox to the cowl (pepto pink version) was very tight. Enough so that I left out the alternate air for lack of clearance. Also, the entire snorkel was a good 3/4" off center. I was at the airport yesterday and decided to trim a small amount from the cowl exit, but if I started short on exit area that could make a difference. Next Time I am at the airport I am going to measure the exit area for comparison.

I make pick up a couple pressure transducers so I can measure plenum vs lower cowl differential.

[BH1166]

I have completed my install up to bending lovers from flat to 45 degrees and riveting down. Not a builder , so question is how to properly bend the tabs/louver. I cleco?d down and am hesitant to try to bend as the material between each opening is not all that stout and afraid it may flex and break. No reason they cannot be pre bent to 45 before riveting in place, just unsure of best way to do. I have access to straight blade seaming plyers......should I lightly score a line to help with bend or should I use some other better method. Have bench vise too. Thanks

[Kyle Boatright]

Originally Posted by BH1166

I have completed my install up to bending lovers from flat to 45 degrees and riveting down. Not a builder , so question is how to properly bend the tabs/louver. I cleco?d down and am hesitant to try to bend as the material between each opening is not all that stout and afraid it may flex and break. No reason they cannot be pre bent to 45 before riveting in place, just unsure of best way to do. I have access to straight blade seaming plyers......should I lightly score a line to help with bend or should I use some other better method. Have bench vise too. Thanks

I used my thumbs, then seaming pliers on mine. I did them off the airplane.

[BH1166]

Thanks Kyle. I took a scrap piece of 2x6 and some drywall screws and mounted it, got fingers under edge enough to come back with borrowed seamer plyers. All finished about remount cowl.

[rv6n6r]

Sounds like you got it sorted but for future reference, never score aluminum for bending (or for any other reason except maybe to mark for a cut) -- that'll just set it up for a crack there in the future.

[BH1166]

Thanks Randell , a good friend and 7A builder texted me the same. I appreciate builders looking out for us buyers