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Exhaust support attachment point

FireMedic_2009

FireMedic_2009

Well Known Member
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I’ve got an RV6 I bought about 18 months ago with the engine disassembled with the crossover exhaust.

So I’ve searched past posts that I was able to find and there were some who attached the supports to the rear of the oil pan and others who attached it to the engine mount. Those who attached it to the oil pan reasoning was the pipes will move with the engine instead of being fixed in place putting less stress on the pipes and support brackets.

First, should the supports be attached to the rear of the oil pan or engine mount?

Secondly, I’ve seen the two pipe tied together with and flat bar or with the same setup as the supports using the 3/8” tube on either end of attached together with a short section of rubber hose. Should the tubes with hose be used so the two pipes can move independently?

Lastly, currently the supports have about a 7” section of hose with spacing between the tubes inside the hose of about 4”-5” which gives it a lot of flexibility. Should the tubes only have about an 1” spacing inside the hose so as to give a little flexibility but not too much?

Thanks
 
FireMedic_2009 said:
I’ve got an RV6 I bought about 18 months ago with the engine disassembled with the crossover exhaust.

So I’ve searched past posts that I was able to find and there were some who attached the supports to the rear of the oil pan and others who attached it to the engine mount. Those who attached it to the oil pan reasoning was the pipes will move with the engine instead of being fixed in place putting less stress on the pipes and support brackets.

First, should the supports be attached to the rear of the oil pan or engine mount?

Secondly, I’ve seen the two pipe tied together with and flat bar or with the same setup as the supports using the 3/8” tube on either end of attached together with a short section of rubber hose. Should the tubes with hose be used so the two pipes can move independently?

Lastly, currently the supports have about a 7” section of hose with spacing between the tubes inside the hose of about 4”-5” which gives it a lot of flexibility. Should the tubes only have about an 1” spacing inside the hose so as to give a little flexibility but not too much?

Thanks
Click to expand...
I am definitely in the camp of attaching the support to the back corners of the sump, allowing the exhaust and engine to move together without too much stress.

The tie between the two pipes should also have some flexibility. I recently replaced my rubber hose and tubing cross tie with a flat bar, BUT, the bar attaches to the exhaust clamps with some generous rubber bushings. Going by memory here, so might not be exactly right, but the holes in the flat bar are 7/16" diameter, and the clamp bolts are AN3 (3/16") The bolts go through rubber bushings that were made by nesting a couple of short segments of rubber hose together. I think the inner piece is 3/16 I.D. and 5/16" O.D. and the outer piece is 5/16" I.D. and 7/16" O.D. The segments are about 1/4" long, and there is a AN970 washer on each side holding the bar captive. The AN3 clamp bolts are tightened just enough to see some visible swelling of the rubber. Like I said, those hose diameters may not be exactly right, but you get the idea. You might also just look for a high-temperature silicone grommet at McMaster Carr that has a 3/16" I.D. and a 3/8" O.D. for example, and put that grommet into a 3/8" hole in the bar, again captured between two AN970 washers.
 
FireMedic_2009 said:
I’ve got an RV6 I bought about 18 months ago with the engine disassembled with the crossover exhaust.

So I’ve searched past posts that I was able to find and there were some who attached the supports to the rear of the oil pan and others who attached it to the engine mount. Those who attached it to the oil pan reasoning was the pipes will move with the engine instead of being fixed in place putting less stress on the pipes and support brackets.

First, should the supports be attached to the rear of the oil pan or engine mount?

Secondly, I’ve seen the two pipe tied together with and flat bar or with the same setup as the supports using the 3/8” tube on either end of attached together with a short section of rubber hose. Should the tubes with hose be used so the two pipes can move independently?

Lastly, currently the supports have about a 7” section of hose with spacing between the tubes inside the hose of about 4”-5” which gives it a lot of flexibility. Should the tubes only have about an 1” spacing inside the hose so as to give a little flexibility but not too much?

Thanks
Click to expand...
Recently I fitted the Van's crossover exhaust to my RV-6A and also attached the hangers to the rear sump bolts, rather than the engine mount, so as to minimize relative movement and potential for cracking.

The two exit pipes are tied together near the firewall by 3/8 tube and a length of hose in between.

The gap between the tubes where they are connected by hose is approximately 1/2", as depicted in the installation instructions. I think that 4-5" would be way too much flexibility to properly support the pipes.

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If you need more 3/8 tube then it is convenient to get steel automotive brake line from a brake repair shop. It is coiled but it is easy to straighten it and flatten the ends in a vise.
 
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Here is the VAF thread where I described making the blade support with rubber bushings to replace the tubes and hose. There are before and after pictures.

low-drag exhaust pipe support blade

Taking a que from Brian Decker (BJDECKER), I decided to try to clean up the exhaust pipe support braces while I am working on the cowl exit. As Brian suggested, I made a blade with elastomeric grommets. I couldn't find Viton grommets, so I made some. I took a piece of Viton tubing, 3/16" ID...
vansairforce.net
 
I don't think its' been mentioned yet, but mounting to the aft sump bolts instead of the engine mount isn't just people's opinion, it's in the instructions that come with the crossover exhaust from Vetterman.
 
Desert Rat said:
I don't think its' been mentioned yet, but mounting to the aft sump bolts instead of the engine mount isn't just people's opinion, it's in the instructions that come with the crossover exhaust from Vetterman.
Click to expand...

The exhaust system I got from Vans in my FWF kit about 2 1/2 years ago was not a Vetterman system. I don’t know who makes it, but the installation instructions and hardware provided has you hanging the 2 tail pipes (crossover system) from the engine mount tubes. There is an alternate way of using flat bar stock to attach to the tail pipes, but that is also attached to the bottom tube of the engine mount.
 

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I put a slight flare on the end of my SS tubes using my flaring tool to provide some “grip” for the rubber hose material with the band clamp. So far so good, but only 200 hours since new/installed.
 
A couple of the brake shops I went to done have that size. The normal size for autos are 1/4”. You can find 3/8” dia at auto parts stores at a length of 30” for close to $10
 
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