I ordered a dual exhaust kit from summit made by hooker headers for my 77 F250. 2.25" pipe, pre bent.

It's a clamp together kit, from the manifolds back

Well, that chit didn't fit, not at all. not up front anyways. lots of cutting, rotating bends, lengthening/shortening between bends, altering bends with my pipe bender etc... Anyways, I ended up doing so much customizing that I just went fully welded instead of clamp fit joints. The pipe turned out just fin in the end, these kits actually fit a 1/2 ton truck of these years just fine, I've used them before

So now onto the mufflers, I chose 2 1/4" inlet/outlet competition turbo mufflers also by hooker headers. I didn't really want loud exhaust, I just wanted duals for better flow and maybe a little more sound than the old single muffler exhaust

After the install was complete I started the truck and discovered that the driver’s side sounded nice, but the passenger side sounded like hell. A clapping rattle sound coming from the RH tailpipe. It could easily be pinpointed to the RH muffler itself. I thought "oh great, just my luck I get a brand new muffler that's got a baffle inside that's not secured, missing weld or something, who knows. But it sounds like a cheap turbo muffler with a busted baffle.

I contact summit and explain it to them, they were very good about it and sent me a replacement muffler along with a shipping label to send the bad one back to them.

So, I cut the bad one out, grind the inlet and outlet pipe back to proper length, fit the new one in, tack it, check for fit/clearance & all that, then fully weld it. I start the truck up and.... Same chit. It sounds like hell, clapping and rattling.

So, what are the chances I've got 2 dud mufflers in a row? The pipes and mufflers are routed very nicely and supported properly, no leaks, good fit at the manifold, pipes not hitting or touching anything, mufflers not touching each other.

Engine is 351M

Any thoughts or suggestions?

 

I know it's a lot of work but what about swapping them, moving the one on the drivers side to the passenger side and vice versa to see if the sound changes/moves?

 

I wouldent be surprised if you got two bad mufflers in a row. I bought some cherry bomb glass packs and the one was perfect and the other was just a hollow tube with nothing in it. Took em both back and got some glass packs called purple hornies. They are made in the USA by flotech.Take both mufflers off and see if the noise is still there.

 

Run it with no muffler and see if the sound is still there, if it is then atleast you have eliminated the dud muffler idea, if it's not there then I guess call summit again....

 

yeah I thought about switching left/right sides with the mufflers or taking both off but damn, it's all welded. If it was a clamp fit I would have tried that by now. I just hate cutting that apart ya know?

I did send summit another email today explaining exactly what I've explained here. I don't know what more they will do for me but I'd honestly rather they sent me something like a pair of 36" glasspacks like the jones weld in blanks. Or credit towards a pair of flowmasters.

I really don't feel like rolling the dice on another one of these hooker turbos.

 

Not really any help here, but i like the dynaflow raptors, might be a little on the loud for ya though, pretty quiet at idle / midrange but when you lay into the pedal you almost think the mufflers dissapear. I like em cuz theyre kinda like auto cutouts in a way i guess lol, on a rear exit setup they may be quiet anyway, i dumped in front of the rear tires on my ranger with a "warm" 5.0.

Dont mean to point out the obivious, but i would definately just tack or clamp the mufflers first go round to make sure everything is kosher, you dont have on backwards do you?

 

Actually these are pretty tough to put on the wrong way, they say they will flow either way with the same results. So I mounted them how they fit best which was center inlet, offset exit possitioned to the high side.

I've got flowmasters on my 69 roadrunner and I really like em.

Right now I'd take loud but nice sounding over clappy/chitty sounding.

These drone at idle, are louder at low RPM and actually seem to clean up and quiet down a little when you get into the gas, very strange.

If they both sounded like the drivers side I'd be ok with it, but the RH muffler sounds like crap.

I'll update when I get a response from summit.

And thanks everybody for the input.

 

Might look into the raptors if they still make em, iirc 29 bucks a muffler and imo best sounding ones there are... fwiw.. i cant stand flowmasters theyre to drony and resonate in the cab constantly.

 

yeah, rear exit in my roadrunner and the high compression 383 is kind of a different air stuffer than the 351M

I'll see what summit has to say. I started the truck again just now to move it and yuck, sounds like crap.

 

Well summit did reply to me today. They are offering to work with me further on the issue by either replacing this thrush turbo with another thrush turbo, or a different type of muffler. What they didn't touch on was whether they would swap me for a matching pair of different mufflers or just this one.

I'm holding off on my reply because I'm trying to determine if i might have a miss on the RH side of the engine.... I'm going to go hook up a low RPM tach (dwell/tach meter) and unplug the RH spark plugs one at a time while running and see if I can pinpoint it. On the LH side I can pull the plug wires one by one and see an obvious difference without a tach, but it's hard to tell for sure on the RH side, seems very strange...

 

I couldn't get a drop in rpm by unplugging any of the RH plug wires individually.

But by pulling them one at a time it seemed that if I pulled #4 plug wire the exhaust tone smoothed out and lost the irregular flutter shown in this video i just shot with my phone.

Video from My Phone - YouTube

This video is a comparison of normal idle with all plug wires attached, RH side vs LH side.

 

I'm going to borrow a compression tester from a friend at work tomorrow.

 

Hold a piece of paper over each exhaust pipe you can even use a dollar bill. If you have a mis fire it will suck the paper back toward the exhaust pipe, works on all cars surprisingly well.

 

I can feel a little pull with my bare hand doing that one pipe at a time. The crossover in the intake is definately open.

So confusing that I can make that irratic flutter go away by pulling the wire to the number 4 cylinder.

The exhaust tone gets pretty smoot but definately weaker sounding than the LH side.

I'll try the paper thing, I'm bored lol!

 

yep, it slaps the paper back tight to the pipe. I think that number 4 cylinder is my trouble.

I'm really starting to think i dont have a muffler problem at all...