Exhausting ??s

[GoldHawg]

As I'm trying to put together my 2.25" exhaust, I'm looking at how to mount my catalytic converter in my small space in the cross member and to get the cat centered, I would like to rotate the body slightly above the X mbr. ?#1, how much room is there between the floorpan and the Xmbr at that location? 2nd question is how much concern over having one end even closer to the floorpan for heat? Any add'l heat mitigation steps needed/possible? ?#3, I have less room than I'd like with the current collector on my custom header to have a long flex tube. But I do have room for a 4" in front of the cat, and then another 4" in front of the exhaust hole connecting to the collector via v-band clamp. I would have a piece of 2.25" tube going thru the Xmbr exhaust cutout hole, and there would be room for it to move perhaps up to 3/8". How do you think 2 flex couplers would work vs one longer one immediately behind the header collector? I could shorten the collector, but the longer I can keep it, the better performance the merged collector provides.

Also, I am currently planning on fairly rigidly welding the exhaust to the frame starting at the cat all the way back, just using the vibration isolators like these:
https://www.summitracing.com/parts/stw-uh2-5w/overview/
?#4, Is there any reason why the cat back part of the exhaust needs more flex beyond the vibration control given by these?

[tjp]

First thing that comes to mind for me is why are you putting a catalytic converter on a vehicle that is nearly, if not over, 50 years old? Surely you don't have to pass smog in Ohio with a vehicle that old?

[GoldHawg]

I like to be clean; aside from the environment, I don't like the smell. I have dual cats on my 71 Cutlass as well. Modern cats don't cost that much in output and much cleaner.

[keith0alan]

My first thought is the cat will be right below your seat. Particularly on carbed cars they can get amazingly hot. What are you doing for heat shielding?

[spl310]

Nissan revised the exhaust on the cars in 68 see this:

http://datsunroadster.com/PIC_PAGES/PAR ... t_info.htm

[GoldHawg]

What are you doing for heat shielding?

That is my question seeking your advice!!!
The cat does have the shield above it that is welded on top (the side you see), but I definitely would add more pending counsel and ideas.

[theunz]

One word comes to mind....FIRE!! Catalytic converters are known to get hot enough to start grass fires. Unless your running 22s your roadster is going to position the cat much closer to the ground than any production vehicle. Even free flow mufflers can transfer a substantial amount of heat to the floorboard. Since there will be very little clearance between the cat and the frame you'll need to find a thin but efficient heat barrier, oh yeah, don't park in the grass
As to the flex pipe, I would think that just a short one at the header would be sufficient, as you are mainly just trying to dampen the movement from the engine.

[Alvin]

First thing that comes to mind for me is why are you putting a catalytic converter on a vehicle that is nearly, if not over, 50 years old?

It cuts down on the exhaust smell.

[Alvin]

you could use a smaller cat, like Spriso:




Shannon's

We add heat shielding on the floor, and then a double layer of Dynamat and that seems to work out quite well.

Michael

[GoldHawg]

Thanks for initial thoughts, but I still need answers to my ??s. If anyone has info on these specific ones, please chime in:

• how much room is there between the floorpan and the Xmbr

• Any add'l heat mitigation steps needed/possible?I saw Alvin's note from Spriso, but would love to see exactly what kind of heat shielding was done and where it was applied--relates to the first question

• How do you think 2 flex couplers would work vs one longer one immediately behind the header collector?

• Is there any reason why the cat back part of the exhaust needs more flex beyond the vibration control given by these

[bikermike]

For some thin insulation consider DEI Floor and Tunnel Shield

viewtopic.php?f=3&t=24855&hilit=Dei#p223738

[bobd]

I got something similar to this and made some brackets to hang it from the frame inside the X area above the exhaust.
https://www.summitracing.com/parts/hsp- ... zgQAvD_BwE

[GoldHawg]

you could use a smaller cat, like Spriso:

that's the answer. Stainless Works makes a very small 3" cat that will be the solution.

[Alvin]

you could use a smaller cat, like Spriso:

that's the answer. Stainless Works makes a very small 3" cat that will be the solution.

very pretty!

[richard]

you could use a smaller cat, like Spriso:

that's the answer. Stainless Works makes a very small 3" cat that will be the solution.

Which Ice engine works set are you using?