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RV14A Lower Cowling Revision for 4 into 2 Exhaust

77bonanza

Active Member
Does anyone have any photos/guidelines for altering the lower cowling on a RV14A from a 4 into 1 exhaust system into Vetterman's 4 into 2 exhaust systems for a IO390-EXP177 A3B6 Thunderbolt engine? Photos would be especially appreciated.

Thanks.
 
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Vetterman's 4 into 2 cowl exhaust cut outs

Start with an approximation of the cutouts that you know will need to be enlarged by way of successive cuts, i.e. start knowing the cut outs will be tight.

I enlarged both of the cut outs at least twice after the first cuts. The cowling is off now to do my first oil change and I will be enlarging the left side exhaust cut out, the photo of the cut out with the line of dots. That cut out is clear of the exhaust pipe but I want more. It should be my last cut out adjustment.

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I started out with the sizes in this pic and made the final a little larger to make sure the engine shake didn't cause the pipes to contact the cowling
 

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Here is how I did mine. I started out with 1/2” clearance all around but opened that up to 5/8” after my first flight due to rubbing at start up and shutdown. FYI this is a 390 EXP60
 

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Not a 14A but this is what I did for he 14 taildragger. Pipes and outlets are more visible in the 3 point position.
 

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Does anyone have any photos/guidelines for altering the lower cowling on a RV14A from a 4 into 1 exhaust system into Vetterman's 4 into 2 exhaust systems for a IO390-EXP177 A3B6 Thunderbolt engine?

Just to clarify...the "EXP177" is the 210 HP version with a one-piece intake plenum/oil sump?
 
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