Good day to all, I am planning the exhaust system for my '78 440 RC and need some opinions.I have purchased a really nice set of Doug Thorley Tri-Y headers for starters.I don't want to deal with header gasket leaks and don't mind spending the extra for Remflex graphite or Percy's Seal-4-Good aluminum ones.Which would you guys use on a normal street truck up to around 400 HP? Reliability is the top priority.Also..bolts or studs? I want this system to go into a single 3" after the transfer case.I think there is room for a Y pipe , H pipe to dual inlet muffler or an X-pipe type deal.I will be doing a fuel/air guage for tuning purposes so the h or x is better in my mind for O2 sensor location....thoughts on this? I also need advice on mufflers.I want a nice deep tone with no droning...maybe Flowmaster 50's...I don't know? ??? Finally, I think the Walker 45105 tailpipe from a 92-93 Cummins truck would be a cheap solution to work with the stock exhaust location...thoughts?This 440 will always be mild and I want nice street manners for it.I do want to put EFI on it eventually but will stick to the existing Holley 4175 that's on it for now.I have attached a photo of a good design I think.Thanks to all!

that looks like it would work out good to me. has good ground clearance/tucks up around things in the chassis.

IMHO..just don't make it to ridge with hangers and don't spread the hangers out to far apart.

hang the pipes/hanger so engine torque/twisting the pipe. ( like a sway bar torsional twisting) does not over stress the hangers or pipe connections.

I have replaced lots of mufflers from welding rod hangers to them and engine torque cracks muff over time with to many making it too ridged for engine torque movement.

engine torque is a whole nother thing with headers, tends to make cheap headers warp/leak. so thick flanges! (light coat of permatex copper rtv and plug injection holes) have always sealed my cheap headers.

try to picture any future R&R of the trans/xfer and the need to R&R the exhaust or try to route it to accommodate R&R trans with out removal.

(kinda sux to have them hang down loose in the way while R&R of trans happens-like it looping under tailend of xfer or blocking trans jack ect.

I have built my pipes in section to un-bolt them front to back and remove pipes from under truck when R&R trans work is needed. buy weld in ball & cone flange connections to unbolt it in pieces.

but the 2.5 into a 3" muff/tail pipe works really well with manifolds or headers. got that on my 89-360 diplomat.

myself I like the magnaflow 99$ muffs. it funny how all my mopar trucks and car have the same exhaust tune/note.

good luck and think ahead on pipe routing.

Thanks scratchn....plenty of hangers and ball and cone connectors everywhere are good practice.Have you heard of the header trick about slotting the outside flange holes horizontally and using studs and cone washers w/nuts?Bolts in all the other holes.

forgot your ?s

yes I think that tail pipe will work out great but may need some trim work due to the shorter wheelbase of a RC chassis or custom pipe work.

I used all studs on my BB truck with a set of hedman 79250 headers

used cheap mrgasket gaskets with some permatex copper rtv on both sides. no leaks in 7 yrs so far.

but with a set dougs tri-Ys I vote remflex

also watch the machined edge/head casting with the header gasket.

I noticed the paper gasket I had used, the ends were notched to "hang" the gasket on the studs while installing but the machined ridge would catch the edge of gasket...when torqued it would put a crease in the gasket and would burn/fail/leak.

flipped it over and it fit flush for no leaks. test fit gasket to make sure gasket is flush on head surface as well as header flange.

I did not slot any holes but I did ream them a little bigger to easy fitting them on the studs.

I used lock washers/nuts on all my studs with no issues.

once I found the gasket issue and it needing flip 180* to be flush around the ports and sit on the machined edge and not hang over it.

oh I always add o2 in the header collector right next to the evac valve so it stays pluged in unless header is R&R

convenient would come to mind on this location me thinks

Can you get those headers for 2wd? I was looking recently for 77 d150 with 440 and didn’t see an offering from doug.

They were used, but in perfect shape...ceramic coated.Unfortunately, you can't get them any more.I was very lucky to find them!

wouldn't be more accurate (both banks mixed)to have it in the X-pipe?

Curious, gas tank in way the reason you're not going with dual exhaust?

I'm looking to do my exhaust too '79 Power Wagon

On the Muffler’s, I had a long thread going in the main tech section. Some good info there. Too bad the setbacks I’ve had have shelved the exhaust project.

Yes, there isn't much room on the driver side

Same here. I have dual tanks. Going to remove under bed tank I think, and just go with in cab tank. I really want dual exhausts.

if running a single 02 yes.

On the topic, what’s the deal with all the 200 dollar SS headers on eBay for these trucks? Chinese knock offs of headman or hooker?

I found this muffler at Dynomax...the X is built inside the muffler. 2 1/2" or 3" is the question. http://www.dynomax.com/mufflers/ultra-flo-welded-x-mufflers Certainly makes the packaging of the system easier.

my vote is for Percy gaskets and hooker aerochambers. When I had them on my truck, the sound off throttle when leaving the freeway was like distant thunder rolling in. Mellow around town, and at WOT was a roar for sure. Every time I went out I got a compliment on the exhaust. I also have the thorley tri-y's, nice score