Exhaust decision, opinions?

[GMJimmy]

I have a 68 C10 SB Fleetside with a 4.8 stock LS engine and Hooker Super Comp long tube headers and a Flowmaster American Thunder system. Just a cruiser, not interested in big power. It's very noisy to the point where you can't listen to the radio on the highway. I'd like to tone it down in the cab and have been thinking of putting some shorty headers on it. I have a pair of Patriot stainless shorties or was thinking of some cast iron manifolds from Summit or Patriot. This will require me to reconfigure the exhaust and relocate the cats. I want it to be quieter in the cab but my concern is I don't want to kill the already limited power It has. Opinions or suggestions are appreciated.
Thanks
Jim

[MikeB]

Originally Posted by GMJimmy

I'd like to tone it down in the cab and have been thinking of putting some shorty headers on it. I have a pair of Patriot stainless shorties or was thinking of some cast iron manifolds from Summit or Patriot.
Thanks
Jim

That's going to make little to no difference in the noise. I'd suggest Walker Dynomax Super Turbos with the 20" case. Fairly quiet compared to anything from Flowmaster, but they flow as well or better.

[ChevyRacefan]

I think just replacing the flowmasters mufflers to walker /etc will fix your issue.
Every Flowmaster I have had ,had a drone at cruising speed

[Mike C]

I have the mufflers MikeB recommended on my Jimmy and they sound great and are significantly quieter than most others. I bought a second set for the big block swap into my C10 as well.

[GMJimmy]

Thanks Mike and ChevyRacefan for the replies. This isn't a drone but more of an engine roar combined with wind noise. I realize these old cabs aren't air tight. At 70 MPH it runs at about 2100 RPM so not screaming. I just thought the long tube headers might be the issue. I might try some dynamat insulation under the carpet and firewall.

[ChevyRacefan]

https://youtu.be/j8CcTYsMHYU..

[MikeB]

Maybe you just need to add sound deadening to the cab.

[LS short box]

Sound deadening will help a lot. I run dyna mat like stuff first. Then double sided foil back with the jute in between and then the carpet.
Another thing is run the tail pipes out to the back of the truck.
You can also insulate the bottom of the cab over the top of where the headers run.

[GMJimmy]

Originally Posted by ChevyRacefan

https://youtu.be/j8CcTYsMHYU..

Got IT!!

[GMJimmy]

Originally Posted by MikeB

Maybe you just need to add sound deadening to the cab.

Originally Posted by LS short box

Sound deadening will help a lot. I run dyna mat like stuff first. Then double sided foil back with the jute in between and then the carpet.
Another thing is run the tail pipes out to the back of the truck.
You can also insulate the bottom of the cab over the top of where the headers run.

Yeah I think the Dynamat might be the partial answer. Thanks.
Jim

[MAC71Cheyenne]

Currently have headers n full Flowmaster duals running straight out the back with turn downs. Wasn't a problem at all but put in Dynamat while doing the interior and am happy with it.The Dynamat will help with heat and noise from everything. LocDoc is checking his pile for a set of rams horns cause I want to ditch the headers and associated issues with a more stock look. Always had good experiences with Walker products in the past if you want to go that way.
*350 w Eldebrock 4bbl and intake.*

[MikeB]

I used Dynamat Xtreme on a 55 Chevy car many years ago. It was very expensive but worked well. When I did my 82 C10 a couple years ago I bought a product called Noico on Amazon. I think it may be slightly thinner that Dynamat, but IMO it works just as well and costs 1/3 as much! It's also available in black. Be sure to use their roller to install it, and some HVAC foil tape at the edges and seams.

Also, no matter what the vendors say, these butyl/foil sound deadening products don't do much to keep exhaust pipe heat from coming through the floor. For that you will need true thermal insulation. I like a product made by Bonded Logic called "Ultra Touch". It is recycled denim strands woven together and backed by foil on one or two sides. Inexpensive and works great! Part numbers for a 4x6 roll are:

#11406 -- single side foil
#12406 -- double side foil

https://www.homedepot.com/p/UltraTou...1406/100656748

I didn't find the double sided version anywhere except at Sachse Rod Shop. Page 102 in their catalog.
http://sachserodshop.com/web_interior.pdf

You can probably find it if you spend more time searching than I did, possibly in Canada.

[Accelo]

You didn't say if you were running and overdrive transmission or not. It is the very best method to quite down these old trucks. If it's not making the noise to begin with it's easy to quite it down.

[GMJimmy]

Originally Posted by MikeB

I used Dynamat Xtreme on a 55 Chevy car many years ago. It was very expensive but worked well. When I did my 82 C10 a couple years ago I bought a product called Noico on Amazon. I think it may be slightly thinner that Dynamat, but IMO it works just as well and costs 1/3 as much! It's also available in black. Be sure to use their roller to install it, and some HVAC foil tape at the edges and seams.

Also, no matter what the vendors say, these butyl/foil sound deadening products don't do much to keep exhaust pipe heat from coming through the floor. For that you will need true thermal insulation. I like a product made by Bonded Logic called "Ultra Touch". It is recycled denim strands woven together and backed by foil on one or two sides. Inexpensive and works great! Part numbers for a 4x6 roll are:

#11406 -- single side foil
#12406 -- double side foil

https://www.homedepot.com/p/UltraTou...1406/100656748

I didn't find the double sided version anywhere except at Sachse Rod Shop. Page 102 in their catalog.
http://sachserodshop.com/web_interior.pdf

You can probably find it if you spend more time searching than I did, possibly in Canada.

I don't have a heat issue, my A/C works well and it DOES get hot here so I pulled the interior out and put Dynamat everywhere. It was a pain working around the A/C and computer and wiring but it's done. I live in a Northern climate now so I won't be driving it for a couple of months. We'll see. Thanks for the suggestions.

Originally Posted by Accelo

You didn't say if you were running and overdrive transmission or not. It is the very best method to quite down these old trucks. If it's not making the noise to begin with it's easy to quite it down.

Yeah a 4L60E so about 2100 rpm at 70 mph. Also electric fans but still too noisy.

[siggyfreud]

Where does the exhaust exit? Is it a clamped or welded system?

Moving the exits as far back as possible will help. Welding up unnecessary clamped joints (keep enough to remove it easily though) will also help.

Short to long headers won't do anything IMO.

Something like dynamat + dynapad will help a lot.

[MARKDTN]

Why do you still have cats? I would think you would have had them tuned out of the ECM when you had it done? Stock engine=no need for headers. Stock cast manifolds will be more than adequate for a 4.8 IMHO.

[Custom 68]

Originally Posted by siggyfreud

Where does the exhaust exit? Is it a clamped or welded system?

Moving the exits as far back as possible will help. Welding up unnecessary clamped joints (keep enough to remove it easily though) will also help.

I was gonna ask this as well. I kind assumed since you mentioned an exhaust "kit" it didn't just dump. If it doesn't exit somewhere behind he rear tires it will have even more chance to drone. I had mine exit right in front of the rear tire and it had a drone with my magnaflow muffler. I added a resonator it helped. Ultimately I ran it to the rear and that fixed it.

[GMJimmy]

Originally Posted by siggyfreud

Where does the exhaust exit? Is it a clamped or welded system?

Moving the exits as far back as possible will help. Welding up unnecessary clamped joints (keep enough to remove it easily though) will also help.

Short to long headers won't do anything IMO.

Something like dynamat + dynapad will help a lot.

The exhaust is all welded except where it meets the headers where it has band clamps, no leaks and exits to the sides just in front of the rear bumper. I installed the Dynamat but haven't test driven it yet.

Originally Posted by MARKDTN

Why do you still have cats? I would think you would have had them tuned out of the ECM when you had it done? Stock engine=no need for headers. Stock cast manifolds will be more than adequate for a 4.8 IMHO.

I had the headers from another vehicle. The engine I got didn't have exhaust manifolds so I decided to use the headers. I agree they don't add much power but they look cool. I have to run the cats because of environmental laws. If this was a factory stock truck I wouldn't need any smog equipment but it's modified and classed as a hot rod so It has to meet the emission laws at the time it was modified. It has a 2002 GMC engine in it so it has to meet 2002 rules. It also has a closed fuel system and evap cannister. I don't have to smog test it but It has to have the equipment.

Originally Posted by Custom 68

I was gonna ask this as well. I kind assumed since you mentioned an exhaust "kit" it didn't just dump. If it doesn't exit somewhere behind he rear tires it will have even more chance to drone. I had mine exit right in front of the rear tire and it had a drone with my magnaflow muffler. I added a resonator it helped. Ultimately I ran it to the rear and that fixed it.

It doesn't drone, It's just loud. A drone is a low tone but this sounds more like a roaring engine but is't running at 2100 at 70 mph. The sound is difficult to explain. Thanks for all the suggestions, I hope the Dynamat helps.

[ChevyRacefan]

Originally Posted by GMJimmy

The exhaust is all welded except where it meets the headers where it has band clamps, no leaks and exits to the sides just in front of the rear bumper. I installed the Dynamat but haven't test driven it yet.



I had the headers from another vehicle. The engine I got didn't have exhaust manifolds so I decided to use the headers. I agree they don't add much power but they look cool. I have to run the cats because of environmental laws. If this was a factory stock truck I wouldn't need any smog equipment but it's modified and classed as a hot rod so It has to meet the emission laws at the time it was modified. It has a 2002 GMC engine in it so it has to meet 2002 rules. It also has a closed fuel system and evap cannister. I don't have to smog test it but It has to have the equipment.


It doesn't drone, It's just loud. A drone is a low tone but this sounds more like a roaring engine but is't running at 2100 at 70 mph. The sound is difficult to explain. Thanks for all the suggestions, I hope the Dynamat helps.

Where is the Air intake for the engine.
Remember the oem used an air filter box with a muffler for a reason on the new donor truck
And newer trucks have more sound deadner than these old trucks.

[BRL]

...um...apparently you all didn't check out my serious killer stereo system...

...the dang thing ROCKS!

[Custom 68]

Since it is just loud I would say a muffler change would be in order. I googled your setup and it said "aggressive sound" so I would say it lives up to its name. Sound and loudness are so subjective. You may need a little modification to fit a different muffler in but it should be minimal. Magnaflow was and is ok, (IMO) but I swapped mine to Borla and really like it. Again it is a subjective.
Dave

[Myself]

-Trucks and SUV's tend to 'drone' in the first place.
-Dynamat or similar product in the cab helps a TON!
-Before spending a bunch of money try installing RESONATORS right BEFORE the mufflers. I've done custom exhaust on a 4cyl and two 6 cylinder rigs of ours. Do you know what a Jeep straight six with a stainless longtube header, no cat, and flowmaster muffler sounds like?!!? Put a resonator BEFORE the muffler and it's a completely different sound....smoother note (not crackly) and half the decibels....no joke! My Nissan Xterra with a 3.3 V6 has stainless mid length headers, one pair of high flow cats, 2.5" pipe, a stainless resonator (just like thesehttps://www.ebay.com/itm/2pcs-Mufflers-Exhaust-2-5-Inlet-Outlet-20-Long-Resonator-Stainless-Silencer/192787047257?hash=item2ce300e359:g:xjkAAOSwmepcCeBU), and a Flowmaster FlowFX muffler! It has a nice smooth, deepish, sound. Not fart canish at all. The guy at the muffler shop said he would NOT have believed it would sound this good if he'd not heard it himself! Also stated he will remember this little trick for smoothing or toning down a raspy exhaust.

[Tomchev]

I have knock off flowmasters on mine with stock manifolds and it's not loud. 71c10 5.3 with mild cam. 2 1/4 inch all the way to the back behind the rear wheels.

[GMJimmy]

Originally Posted by Custom 68

Since it is just loud I would say a muffler change would be in order. I googled your setup and it said "aggressive sound" so I would say it lives up to its name. Sound and loudness are so subjective. You may need a little modification to fit a different muffler in but it should be minimal. Magnaflow was and is ok, (IMO) but I swapped mine to Borla and really like it. Again it is a subjective.
Dave

I bought the truck with the existing exhaust system and who ever installed it welded it in at every joint. The only way to change the mufflers would be to cut them out. I don't really like the system and was thinking of replacing it because at one point it ducks under the cross member the trailing arms are attached to. I wanted to C notch it too but the exhaust is in the way and won't allow the extra travel the C notch provides. I would have to do something with the bed for clearance too. I'm a mechanic and have all the tools and welding equipment to do it but the cost far out weighs the benefits.

Originally Posted by Myself

-Trucks and SUV's tend to 'drone' in the first place.
-Dynamat or similar product in the cab helps a TON!
-Before spending a bunch of money try installing RESONATORS right BEFORE the mufflers. I've done custom exhaust on a 4cyl and two 6 cylinder rigs of ours. Do you know what a Jeep straight six with a stainless longtube header, no cat, and flowmaster muffler sounds like?!!? Put a resonator BEFORE the muffler and it's a completely different sound....smoother note (not crackly) and half the decibels....no joke! My Nissan Xterra with a 3.3 V6 has stainless mid length headers, one pair of high flow cats, 2.5" pipe, a stainless resonator (just like thesehttps://www.ebay.com/itm/2pcs-Mufflers-Exhaust-2-5-Inlet-Outlet-20-Long-Resonator-Stainless-Silencer/192787047257?hash=item2ce300e359:g:xjkAAOSwmepcCeBU), and a Flowmaster FlowFX muffler! It has a nice smooth, deepish, sound. Not fart canish at all. The guy at the muffler shop said he would NOT have believed it would sound this good if he'd not heard it himself! Also stated he will remember this little trick for smoothing or toning down a raspy exhaust.

Thanks for the suggestions but there isn't any room for resonators.

[GMJimmy]

Originally Posted by ChevyRacefan

Where is the Air intake for the engine.
Remember the oem used an air filter box with a muffler for a reason on the new donor truck
And newer trucks have more sound deadner than these old trucks.

The only issue I have there is a whistle at part throttle. I've been meaning to see if the factory filter box will fit under the hood without moving other things out of the way. Right now it has a 5 inch aluminum intake about 2 feet long with a mass air flow sensor and a K&N filter on the end over the left hand inner fender behind the headlight.
Thanks