How To Cure a "Rappy" Exaust?

[ramcharger]

OK, just finished up some brake mods (3/4 ton master and Booster), put in seat belts, rear view mirror, new electric fuel pump (thanks fishy! Works great!), went a 1/4 turn out on my idle mixture screws (now it idles great in gear at 700rpm, yes it's a tight converter), put in seat covers, and swapped out all locks (whew!).

Went for a test cruise and the exhaust has that crappy rappy sound between 2500-4000 rpm. I'm running a a .040 360 with 216-224 duration cam with 1.6 rockers and a 10.2+ comp ratio. Exhaust is summit headers (I think, it's been a while) Flowtech turbo muffs and full 2 1/2 pipes. Sounds like damn lowered heavy chevy with a small block, glass packs and 1 3/4" pipes. When it's rappin, it's pulling real hard and this is a 4800 lbs truck, dry and without my fat *** in it. May as well call it a 5015 lb truck, lol!

It is my Ramcharger with 3.55 gears and 33" tall tires. The exhaust pipes themselves are 11' long including mufflers but not including all the bends (just measured in a straight line).

Would adding some 12" glass packs at the *** end on each pipe quell the rap or would it just make it worse? Should I have gone 3" since the exhaust is so long? Is just the shitty Flowtech Turbos?

I do plan on doing an entirely different set up in the future, but I just need to get this sucker ready to tow my Duster to my new place without attracting the attention of the local ticket distributors. The rap is so loud that I goosed it on the frontage road and I saw people on the highway turning to look, lol! OK, it's kinda cool sounding, but I still don't need people two-three blocks turning around and thier dog jumping a foot high 'cause I gave it some juice. It as if there are no mufflers and I'm runinng straight pipes.

Thanks in advance! Oh yeah, a crossover is not in the plans for now or the future due to clearance. I need all the clearance I can get to get to my favorite fishing holes with this thing. Right now I can toss a Snap-On rolling stool right under the sucker with no chance of hitting whatsoever. Here's what sounds like in stationary condition:



I've done some tuning since (timing and mixture) and it sounds better now too. You can hear a bit of the rap there, but it's extreme under load.

Please note the awesome job Leanna did powder coating the Alt and brackets too!

 

[SwinginDart74]

I had the same problem on my 91 GMC, I had 2.5" duals straight out the back like you with long cherrybomb glasspacks, I put some 3.5" dia by 14" long chrome tips on, took the tommy gun sound away, make sure they have the rolled lips, made my 350 sound like a big block

 

[ramcharger]

I had the same problem on my 91 GMC, I had 2.5" duals straight out the back like you with long cherrybomb glasspacks, I put some 3.5" dia by 14" long chrome tips on, took the tommy gun sound away, make sure they have the rolled lips, made my 350 sound like a big block

Thanks! I'm guessing this is due to the length of our truck exhausts and I'm glad to hear I'm not the only one to experience this. The "Tommy Gun" sound is exactly what I'm experiencing and it's very attention getting.

When you say rolled lips, do you mean rolled in to the tip? Got a link to a product? I haven't seen tips that long here at the local parts places. Just the short fat "fart can" import crap.

 

[rumblefish360]

I don't think a glass pak would be a great idea. Resonators ethier in line with the pipe or like this page at Sumitt; http://store.summitracing.com/egnsearch.asp?N=700+4294923429+115+4294922678&NeXID=5

Pace Setter tip; http://store.summitracing.com/partd...&N=700+4294923429+4294922678+115&autoview=sku
Headman tip; http://store.summitracing.com/partd...&N=700+4294923429+4294922678+115&autoview=sku
Flow tecs; http://store.summitracing.com/partd...&N=700+4294923429+4294922678+115&autoview=sku
Headmans pictured below.

 

[ramcharger]

Thanks Rumble,

I'll look those up and see what I can afford right now. I'm tempted to make make own 18" long 3 1/2" dia. tips and see if that helps. I figure I can get 36" of 3 1/2" pipe and a couple of reducers for cheap.

This won't be permanent, just until I can get my situation in order.

 

[AdamR]

A cross over pipe will help. X or H.

 

[memike]

Thanks Rumble,

I'll look those up and see what I can afford right now. I'm tempted to make make own 18" long 3 1/2" dia. tips and see if that helps. I figure I can get 36" of 3 1/2" pipe and a couple of reducers for cheap.

This won't be permanent, just until I can get my situation in order.

Glad to see and hear you are moving forward ramcharger.
If anyone can fab something, I have seen your handy work and I bet you will come up with something great brother :cheers:

I agree a pair of cannons will do the trick.8)

 

[grimreaper]

My pickup had that annoying rap to it too. 2-1/2 pipe turned out behind the rear wheels. Tried several different mufflers, glasspacks and several other things but only got the thing to sound decent when I installed a crossover pipe. I was reluctant for clearance issues too. You can fit one up nice and tight if you plan the routing. Mine ran exactly in front of the transfer case skid plate. Never scraped the crossover once through a lot of serious 4-wheelin' in the mountains. (which did require the Warn winch on several occasions) Sounded great with the crossover and magnaflows. Nice deep purr that turned to a deeper growl on acceleration...none of that overly rich Chebby rappin'........

 

[66340SEDAN]

Flowmasters baby! I have 2 1/2 pipes with flowmasters, wouldn't have it any other way!! Here are a couple sound bytes with the Flowmaster muffs and 340 power. 8)

 

[Bigmacdak]

I agree with 66340SEDAN. I would put a set of 50 series delta flow flowmasters on it & drive. The 50 series is a quieter muff. than the 40 series, but its not too quiet. & like Adam said, a good H or X pipe will compliment it as well. Flowmaster all the way!

 

[65Val]

Funny how it's mostly trucks that do this. I had a F*rd pickup with a warm 466 in it that did the very same thing. I hated the sound. The only thing that cured it was a cross-over pipe in the headpipes. In my case it was a Dr. Gas X-pipe. I was running Dynomax Super-Turbo's at the time. It made the same noise in town, but, curiously, at hi-way speeds, you could hardly hear the engine,,, till you hammered it to pass someone. It actually seemed like it increased the torque down low.

 

[ramcharger]

A cross over pipe will help. X or H.

I'm trying to avoid that right now due to the money situation. You're right though, a crossover should give low end torque a boost which would be a good thing for this build and will most likely knock the rap out.

Glad to see and hear you are moving forward ramcharger.
If anyone can fab something, I have seen your handy work and I bet you will come up with something great brother :cheers:

I agree a pair of cannons will do the trick.8)

Thanks for the vote of confidence Mike! We'll see if this works or not. Hopefully it won't bring the rap up from "tommy gun" to "automatic cannon" status! Might be an interesting experiment.

My pickup had that annoying rap to it too. 2-1/2 pipe turned out behind the rear wheels. Tried several different mufflers, glasspacks and several other things but only got the thing to sound decent when I installed a crossover pipe. I was reluctant for clearance issues too. You can fit one up nice and tight if you plan the routing. Mine ran exactly in front of the transfer case skid plate. Never scraped the crossover once through a lot of serious 4-wheelin' in the mountains. (which did require the Warn winch on several occasions) Sounded great with the crossover and magnaflows. Nice deep purr that turned to a deeper growl on acceleration...none of that overly rich Chebby rappin'........

Thanks Reaper,

Once I do a complete exhaust on this, I'll take a peak at how much room I have to add a crossover. Not only am I concerned about clearance, but ease of maintenance too. I don't want to have to cut the exhaust if I need to drop the trans/T-case. Maybe a removable crossover is in my future plans?

Flowmasters baby! I have 2 1/2 pipes with flowmasters, wouldn't have it any other way!! Here are a couple sound bytes with the Flowmaster muffs and 340 power. 8)

Thanks 66340! I saw your previous posts this past week and your ride sounds great! I think that it's the length of the entire system in conjuction with the restrictive muffler shop bends that's making it "Rappy" rather than the mufflers.

I agree with 66340SEDAN. I would put a set of 50 series delta flow flowmasters on it & drive. The 50 series is a quieter muff. than the 40 series, but its not too quiet. & like Adam said, a good H or X pipe will compliment it as well. Flowmaster all the way!

I'm starting to agree that a crossover would do the trick, lol! Just can't do it right now is all. A complete re-vamp will be in the works to compliment the new engine and I will most likely go with the FM 50 series when the time comes.

Funny how it's mostly trucks that do this. I had a F*rd pickup with a warm 466 in it that did the very same thing. I hated the sound. The only thing that cured it was a cross-over pipe in the headpipes. In my case it was a Dr. Gas X-pipe. I was running Dynomax Super-Turbo's at the time. It made the same noise in town, but, curiously, at hi-way speeds, you could hardly hear the engine,,, till you hammered it to pass someone. It actually seemed like it increased the torque down low.

It's got to be the length in combo with crappy restrictive bends and a higher compression engine that's creating this sound. I was under the truck last night (and most of the day, lol!) and noticed that the bends cut the diameter almost in half. This is the same exhaust I was using previously with a stock compression engine and a XE262 cam and noticed no rappyness.

When the time comes, I think a 3" exhaust in combo with the FM 50 series mufflers and some type of removable crossover will be key in getting the sound and performance I want.

Thanks again everyone for all of your ideas.

 

[cavemanmoron]

As others have suggested a crossover "H" pipe is the easiest fix.

You could also use "Stock" type muffler to choke the noise away,
but NAH, that would cut down on power.

I have No crossover either.

Hmm my youtube video isn't working for me, hope it works later.

http://www.youtube.com/watch?v=Ud8mci4rjFU

 

[ramcharger]

I was going to fab up some long tips but adapters are not readily availible. I did find some 2.5" to 3.5" 11" long tips made by Hooker at Summit racing. I installed them last night and here are the results:

They did cut some of the rap out but it's still there. The rap seems to have deepend too and it's not nearly as annoying/attention getting. It is louder at idle and at WOT, but it's much more pleasant sounding. Strangely enough, it seems much quieter at cruise and mild throttle application. I think they dropped the frequency of the exhaust to a point where the human ear is less sensitive.

I would think, judging by these results, that a longer tip as was suggested earlier by swingingdart would take even more rap out. I also believe that a crossover like everyone else suggested would eliminate it entirely. I'll keep updating this as changes are made. It'll be awhile though, lol!

 

[fishy68]

I had the same problem on my old Dakota with the 318 when I had true duals installed. A crossover helped tremendously and made it a little quiter. I know your not wanting to do that but I just thought I'd throw in another vote for the crossover.

Recently my Flowmaster 40 with dual outlets on my 02 4.7l Dakota rusted out and I replaced the system with a mandrel bent cat back system with dual tailpipes. At the same time I took off the 3rd. catylitic converter (lucky here we don't have inspection). I used a FM 50 this time since I was taking out the 3rd converter and didn't want it to be any louder. It is about the same volume but is kinda raspy sounding. Not nearly as good as the 40 sounded. But it is quieter. Larger tips helped a little but not greatly.