Tip: Clip-on Air Dam

[Ironflight]

The Valkyrie has always had a very nice, even distribution of Cylinder Head Temps, right out of the box ? the baffle kit back then didn?t have air dams as part of the stock setup, and the recommendation was to go without them, and add them if required. I never needed to, so I never did. But ever since I changed all four cylinders a few months ago, the #1 CHT has run about forty or fifty degrees cooler than the others. Don?t? ask me why ? same baffles, same sealing system ? just Lycoming jugs versus ECI?s.

I?ve been so busy with so much flying (RV-1, RV-3, SnF, Osh?) that I just now got around to doing something about it. I had been putting it off because I was going to have to remove the front baffles in order to install nutplates to hold various dams?and then I let my ?lazy man? inclinations take over, and figured out that I could probably use the cylinder fins to my advantage - allowing me to quickly remove/trim/replace/test. I started out with a 1? wide strip of .032 scrap, and bent tabs on the ends that matched up with fin slots on the #1 jug. I then put a ?kink? in the tabs so that they wedged in ? effectively, I had a clip. I flew with just that in place, and discovered that I needed a bigger dam, so I took it off, cut out a piece of 0.040, and riveted it on to the clip. This popped right in place, and pretty much brings all four jugs to within fifteen degrees of each other ? problem solved! I was ready to trim it down if I needed to make further adjustments, but I think I?ll fly with it like this for now.







Of course, once I know the final size, I can take the baffles off and install nutplates, make a permanent dam, etc?. But that ?Lazy man? just keeps saying ?hey, if it works?.? 

Paul

[Rupester]

Great idea, Paul. Thanks for sharing!

[Greg Arehart]

Looks like you need a new benchtop!

Greg

[bullojm1]

I found that using aluminum tape is an even lazier approach! The first application lasted 90 hours in two years before it started to crack and deteriorate. I was planning on putting in the real aluminum blockers, but it was just too easy to re-tape!

[az_gila]

Paul,
Is there a reason for blocking off the cylinder head portion so much and leaving the cylinder fins alone?

[Ironflight]

Originally Posted by az_gila

Paul,
Is there a reason for blocking off the cylinder head portion so much and leaving the cylinder fins alone?

Lazy man approach - it was the easiest place to start!

I was going to try the tape approach, but got a little worried about the temperature rating on aluminum tape's adhesive - I did a little burn test, and it seemed to support combustion, so I got nervous and went with the clip-on aluminum.

I just got back from a round trip to Pensacola, and temps were pretty nice - might try blocking the cylinder as Gil suggest, just to see what happens.

[kevinh]

Originally Posted by bullojm1

I found that using aluminum tape is an even lazier approach! The first application lasted 90 hours in two years before it started to crack and deteriorate. I was planning on putting in the real aluminum blockers, but it was just too easy to re-tape!

+1 for tape. Worked great for me as I was making adjustments. Once I had things just how I wanted, I made an aluminum dam and riveted it in.

[scsmith]

I might be a bit concerned about vibration making the clips slowly (or maybe not so slowly) chafe into the fins. I suppose it is aluminum on aluminum, but the 2024-T3 is a bit harder than the casting. It should be easy to keep an eye on them and see what happens......

[Ironflight]

Originally Posted by scsmith

I might be a bit concerned about vibration making the clips slowly (or maybe not so slowly) chafe into the fins. I suppose it is aluminum on aluminum, but the 2024-T3 is a bit harder than the casting. It should be easy to keep an eye on them and see what happens......

Yes, I have given that a thought - but I fugure this is just temporary until I pull the cowling next time and take a few minutes to make it permanent (I joke just a little about being too lazy....I'll make it permanent). On the other hand, I've also watched auminum baffle material rub against cylinders for a long time, and it doesn't amount to a great deal of wear, so short term, I have no worries.

Remember that the intercylinder baffles are essentially held on with a spring clip against the clylinder fins - take a look for chafing next time you have them off - they really don't hardly scratch the paint.

Paul

[terrykohler]

Were you able to swap out the thermocouple before tackling the air dam? You're likely going after the root cause, but I'd probably want to verify that the couple is still giving accurate info.
Good Luck,
Terry