Fenderwell header questions

After careful review, and discussing the options with a few trusted mechanics I know, I am opting to go with fenderwell headers in my MB/Chevy 4.3 V6 project. While Sanderson does make a shorty header, there is still a high probability of having steering interference issues with my set up. Pros of the fenderwells include:

1. Plenty of room for steering, starter, master cylinder, and oil filter
2. Space to mount the battery under the body behind the passenger seat, and maybe even a 2nd battery/isolator setup for running the winch or other accessories
3. May be able to relocate the fuel tank underneath instead of taking up valuable cargo real estate

What I dont know is how having the mufflers under the driver/passenger seat will effect felt heat during the summer. It gets pretty warm here in SoCal. Any flat fenders out there running mufflers directly under the driver that can comment or provide info?

 

Not a flattie, but I have the mufflers under the driver/passenger. Haven't noticed any heat concerns. I can post a few pics tomorrow.

 

I've got the mufflers under the driver/passenger on my '70, and just painted metal floors with lots of holes in them, and I really don't notice any excessive heat coming off of them. I'd have to go look, but I'd figure there's about a 1 to 1-1/2" air gap between the muffler bodies and the hat channels.

 

again not a flatty but 304 and fenderwell headers not much heat but watch the pipes on your calf

 

Heat Rises ....................as long as your driving all the time no big issue.........If it's Winter Time & cold and your out on the trail putting along , you'll like it...........In the summer on the trail Idling behind others it will get HOT inside!.....I've seen many techniques like a secondary metal heat shield or even the heat resistant foil packs used in Race Cars used under the tub...........It's the Big heated Muffler sitting under you that causes the heat problem........if you can just have the single Pipe run along the outer rail and then snake it back under the frame rail and have the muffler mounted under near the rear axle that helps!................Can't get away from the Heat Rising!

 

Last summer I still had the under seat tank with a muffler right under it. I had a good 3 inches clearance, but the fuel got really hot and would cause a significant amount of expansion. It was not ideal.

 

My issue was: I had problems with ripping the mufflers off when it was outside the frame. That and noise. I went with a single exhaust tied together behind the transfer case into the muffler. (Behind drivers seat.) Then up and over the rear axle and exiting out the right rear corner

 

Just throwing a pic in here. I have small oval mufflers ( sorry, don't know the brand) Not noisy as the pipes are run out to the back.

 

Thanks for the opinions guys. I use this thing about 60% trail, and it is hot down here, so it is a consideration. It has me thinking about trying the shorties first though, and then determine if I
A) Have clearance for steering
B) Want to modify the steering (add a 3rd universal and heim joint) if it doesn't.

Can anyone post pictures of fender well exhaust on a flatly? Specifically from the wheel wells? Thanks

 

If your using a fuel injection set up you will need a high pressure pump. I would not use an in-line pump. The noise will drive you nuts! Move your tank under and use an in-tank HP pump. It's a lot of work, but worth it. I put a Chevy LT1 in my 1968 PU and used an in-line high pressure pump. The worst mistake of the build! It's terrible. Now I need to go back and change it. I always say: why do it right the first time, when you can go back and do it over later. My 2 cents.

 

On my '45 GPW. I routed my "fender well" headers onside of the frame but inside the fenders. The primaries pass thorough the pocket that is formed by the body and fender. The collecter is located just beyond the fender under the floor. By doing it this way, I did not need to cut holes thorough the fenders and they are tucked up out of the way. I can get pictures Monday if you want.

 

Which headers did you use? Or did you make your own?

Yes please!

 

No matter what, I would suggest the ceramic coated headers. There is a lot of heat and it helps a great deal. Even if you find a used set that fits, or something you can modify. You can have them coated in Fresno. There might be somewhere closer.

 

I built my own. I will post pictures when I get home. Also having the headers coated will help control heat although I didn't do that.

 

Awesome. This idea intrigues me and may be a "best of both worlds" solution. I found someone on ebay selling 3/8" laser cut flanges for my 4.3 for $40.

 

If need be, I can get a better picture showing the header flange. At the moment this is what I have. It's a busy area but there is ample clearance.

Looking down on left side header


Below drivers side looking up into fender well pocket


From side looking at left side header


Looking at left header

 

Awesome, thanks for the pictures. If I cant figure out how to get the exhaust to stay inside the frame rails, I will most likely go that route.