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'72 K5 - Greg's @MightAsWellK5 Build

This is the build description. I will improve this later. (GB)
Overview Gallery Discussion
JoshHefnerX said:
Most factory systems have resonators, to help keep them quiet. You did want quiet didn't you?

Also, resonators if big enough can change the tuning of the system.
Click to expand...


Yeah, I want quiet.

The two variables I'm not sure of

1. The Walker QuietFlow3's are reported to be AS quiet as an OEM-style muffler. They are enormous canisters (at least one of them is) so assuming it flows well enough not to kill power, it MIGHT be quiet enough on it's own that resonators aren't necessary.

2. The other one that looks interesting is the Dynomax VT which has an internal spring-loaded flap that opens up under WOT to let the engine make some noise. Allegedly, under part-throttle cruise or light around-town driving the muffler is nice and quiet and polite. This sounds like the mechanical equivalent of the "electric cutouts" idea I wanted to do... I can make noise and be rowdy if I want to, but I don't have to punish my eardrums ALL the time.


I'm listening to sound clips on YouTube to try to figure it out, but that's just about useless to get a true sense of how anything is going to sound in real life.



-G
 
Personally unless the engine is running trying to pick a muffler is a waste. I think aside getting the routing done and reserving the space for a planned system are great especially if you make it "tweak able" so when you do have it running you can adjust it how ever you want to suit your tastes, but trying to see how a muffler is going to sound is almost impossible, I've tried to do this a million times and they always sound different.

Heck I swapped engines once in my 72 and the truck got twice as loud.. It went from pretty quiet to holy crap that's almost too loud.. Inside it wasn't but outside it was stupid.
That motor only made 240 horse, 2.5 straight back as duals with a balance pipe 1.5 in to dual flowmaster 40s kicked out before the rear tires at an angle away from the cab.
Dumped it was so bad it would rattle the dash.
I've used the dynomax race bullets before and they clean up the sound but on a minimal level, I'm not sure what you are expecting that small of a resonator to do but if you are searching for reduction in total volume id be looking for a resonator with a larger case. Almost like the size of a 10 series flowmaster.
 
sreidmx said:
Personally unless the engine is running trying to pick a muffler is a waste. I think aside getting the routing done and reserving the space for a planned system are great especially if you make it "tweak able" so when you do have it running you can adjust it how ever you want to suit your tastes, but trying to see how a muffler is going to sound is almost impossible, I've tried to do this a million times and they always sound different.

Heck I swapped engines once in my 72 and the truck got twice as loud.. It went from pretty quiet to holy crap that's almost too loud.. Inside it wasn't but outside it was stupid.
That motor only made 240 horse, 2.5 straight back as duals with a balance pipe 1.5 in to dual flowmaster 40s kicked out before the rear tires at an angle away from the cab.
Dumped it was so bad it would rattle the dash.
I've used the dynomax race bullets before and they clean up the sound but on a minimal level, I'm not sure what you are expecting that small of a resonator to do but if you are searching for reduction in total volume id be looking for a resonator with a larger case. Almost like the size of a 10 series flowmaster.
Click to expand...


I know that typically people add a 3" resonator to a 3" exhaust (3" resonator is usually a 4" case)... But there's no reason why I couldn't dump the 3" exhaust from the header collector into a larger 4" (or larger) resonator by using a concentric tapered SS adapter (saw those today while shopping). That would give me more volume inside the resonator and might make it more effective? :dunno:

Anyway, the idea of making the exhaust system modular means I can experiment and try different combos until I find something I like......or my wallet finally gives out! :haha:


-G
 
If you think theres any possibility you'll end up changing mufflers or resonators, build the whole system so you can replace short sections. You can get the piping done and swap in parts to your hearts content.
 
JoshHefnerX said:
If you think theres any possibility you'll end up changing mufflers or resonators, build the whole system so you can replace short sections. You can get the piping done and swap in parts to your hearts content.
Click to expand...

That's the idea.... A v-band clamp on either side of the resonator and a v-band clamp on either side of the muffler.... :waytogo:

As long as I build the system for the "longest" possible resonator / muffler, I can swap in smaller units (with small sections of 3" welded to the ends to make them identically long (from clamp to clamp)... Literally, just loosen two clamp bolts, drop out the muffler...swap on the new muffler....slide the clamps back over and tighten two nuts back down.

-G
 
I was going to suggest to stepping the exhaust because the expansion causes cooling but promotes flow, I just wonder if the outgoing 4-3 inch side would cause problems for you. I would think using a 4 inch system would bet you the flow you are seeking and require but not kill it so much in the search of it being quiet.
 
V-bands are fantastic.

Id build it with resonators from the beginning. Can always make it louder, harder to get quiet, 3" will be hard to get quiet. I have a stainless 2.5 system on my caddie with a Traditional muffler, and I can hear my wife drive down the street and that's a super charged 6.2l small block.
 
ClassicStyle said:
V-bands are fantastic.

Id build it with resonators from the beginning. Can always make it louder, harder to get quiet, 3" will be hard to get quiet. I have a stainless 2.5 system on my caddie with a Traditional muffler, and I can hear my wife drive down the street and that's a super charged 6.2l small block.
Click to expand...

CTS-V? :bow:

-G
 
Greg72 said:
That's the idea.... A v-band clamp on either side of the resonator and a v-band clamp on either side of the muffler.... :waytogo:

As long as I build the system for the "longest" possible resonator / muffler, I can swap in smaller units (with small sections of 3" welded to the ends to make them identically long (from clamp to clamp)... Literally, just loosen two clamp bolts, drop out the muffler...swap on the new muffler....slide the clamps back over and tighten two nuts back down.

-G
Click to expand...
Sounds like how I need to do transmissions. :haha:
 
Greg72 said:
@folkenheath
@ClassicStyle
@EveryoneElseInterested

Here's my research thus far for mufflers and resonators:

Mufflers.jpg



The top line is the current placeholder in my framerails (Flowmaster 70-series). It a huge mother, and since it fits...pretty much anything else I choose should fit also.

I'm trying to stay focused on 3" (center in / center out) mufflers since those will be the simplest to connect to other exhaust tubing and if I end up building flanged connectors for everything it will make "swaps" between different muffler types a cinch!!! :waytogo:

I think I've captured the majority of stuff that is supposed to be "QUIET" and relatively free-flowing, but if I'm missing something let me know.

Since I've got all the tubing to build the entire exhaust system (front to back) I want to select a resonator first....then graft that in as far away from the header collector as I can fit it (while still staying inside the torsion box area)... then I need to make a crazy 90-degree turn to get to the inside of the framerails, and another 90-degree turn to hit the inlet side of the mufflers... I'm using 3" tubing throughout with a 6" CLR bend, so I'm hoping the restriction will be minimized. Throwing a few turns into the mix will probably help to quiet things down a bit so that's a nice side-effect. :)



-G
Click to expand...


I didn't realize the XS isn't made in center in/out 3", they do make the XR-1 in that configuration, it has the stainless packing...

https://www.borla.com/products/xr1_...er_16x45x788__racing_muffler_part__40944.html

If you want it real quiet, can you fit more than one muffler in? My father cut two mufflers apart and welded tthem together on each side back in the 70s to make it quieter. That wouldn't be necessary, could be two mufflers in two different locations if you are really trying to quiet it down. Maybe one oval and one round to make them fit. Like one of the above and one of these...

https://www.borla.com/products/xr1_..._15x5_round___racing_muffler_part__40085.html

The larger volume the case the more sound you can absorb, so running two mufflers might be what you need.

Or if you have a lot of room and a big wallet you could run a pair of these behemoths, ha ha....

https://www.borla.com/products/xr1_...er_34x85x55__racing_muffler_part__400115.html

You may have to make a tradeoff (just like everything else). The fiberglass packing is slightly quieter when new compared to stainless packing, however, the fiberglass packing will wear out and get louder with time. The stainles packing will still be quieter than chambered most likely (assuming equal case size), but will not wear out. Stainless chambered should never wear out and won't change with time, and I think it sounds the best, but it will not be as high of flow like a straight thru borla. Most packing style mufflers use fiberglass, Borla uses stainless in some of its mufflers, like the XR-1.

Those walker mufflers will be quiet, but they will not flow as much as you want because it redirects the flow back through the muffler several times before exiting. I would not consider them a straigh thru design like the borla or ultraflow or hooker max flow.
 
folkenheath said:
I didn't realize the XS isn't made in center in/out 3", they do make the XR-1 in that configuration, it has the stainless packing...

https://www.borla.com/products/xr1_...er_16x45x788__racing_muffler_part__40944.html

If you want it real quiet, can you fit more than one muffler in? My father cut two mufflers apart and welded tthem together on each side back in the 70s to make it quieter. That wouldn't be necessary, could be two mufflers in two different locations if you are really trying to quiet it down. Maybe one oval and one round to make them fit. Like one of the above and one of these...

https://www.borla.com/products/xr1_..._15x5_round___racing_muffler_part__40085.html

The larger volume the case the more sound you can absorb, so running two mufflers might be what you need.

Or if you have a lot of room and a big wallet you could run a pair of these behemoths, ha ha....

https://www.borla.com/products/xr1_...er_34x85x55__racing_muffler_part__400115.html

You may have to make a tradeoff (just like everything else). The fiberglass packing is slightly quieter when new compared to stainless packing, however, the fiberglass packing will wear out and get louder with time. The stainles packing will still be quieter than chambered most likely (assuming equal case size), but will not wear out. Stainless chambered should never wear out and won't change with time, and I think it sounds the best, but it will not be as high of flow like a straight thru borla. Most packing style mufflers use fiberglass, Borla uses stainless in some of its mufflers, like the XR-1.

Those walker mufflers will be quiet, but they will not flow as much as you want because it redirects the flow back through the muffler several times before exiting. I would not consider them a straigh thru design like the borla or ultraflow or hooker max flow.
Click to expand...


Interesting!

So here's the deal: I can TOTALLY fit a full-size oval muffler in two different places on both sides of the truck.... The Flowmaster that I have now (#52571 22" x 10" x 5") will fit in the torsion box area and also fits between the rear framerails just ahead of the new fuel tank. So I can run a total of 4 mufflers if that's a better way to go. The tradeoff is that I can't get any resonators in there with the 4 mufflers....so the 1st set of mufflers would presumably be taking on those duties? The other catch is that the torsion-box muffler ends up pretty close to the header collector (where the gasses are still pretty damn hot) and I know you warned me that it not ideal. I "might" be able to squeak an 18" header extension between the header and that first muffler...but that's about the limit for collector extension length given my packaging constraints.

I like the idea of stainless packing material over fiberglass for sure, and I also prefer getting full-stainless mufflers as opposed to an aluminized steel.

Would a set of four Borla #40944 (16" x 4.5" x 7.88") mufflers be the right approach, or is there a different combination that would make more sense? I can definitely fit a 22" long canister if necessary....and it seems like I really need to focus on maximizing case size to get as much quiet as I can.


-G
 
Anyone know the difference between the following Borla types:

Multi-core (ie: #40575) 3" Oval / 16" x 4.25" x 7.88" $316 <- For "Full Bodied Cars"
Sportsman (ie: #40944) 3" Oval / 16" x 4.5" x 7.88" $174
Heavy Duty (ie. #400436) 3" Round / 24" x 6.75" <- Listed under their "Specialty" section. May be a good choice as a resonator depending on the internal construction / packing materials? :thinking:

What makes a Multi-Core version a "Rotary Engine" part number (ie. #400371) - I assume it's because rotary engines have a sh1tload of high-frequency raspiness that needs to be dampened out? :dunno:

Also.... Borla puts the "sound" of their mufflers into three categories:

  • Touring - Mild, Aggressive Growl
  • S-Type - Agressive Plus
  • ATAK - Super Aggressive
Unfortunately these ratings only seem to be used to describe their Pre-packaged "kit" solutions, and they don't attach these same ratings for the standalone mufflers that I'm looking at above. I've listened to the sound files (Borla actually does a nice job of recording idle, launch, interior acceleration , interior steady throttle, and fly-by) and the Touring is definitely the one I like the best. It's got a nice rumble but almost none of that really raspy high-RPM or lift-throttle crackling that the aggressive systems do.



-G
 
Although not ideal, I think if its a full flow muffler it won't hurt you much being closer to the collector. A full flow borla may actually out flow a resonator if its just a chamber that gets larger and smaller as the steps create turbulence. Because the borla has a peforated tube inside the same diameter as the pipe, it creates a kind of boundary layer to keep the gases flowing in the same direction while letting some of the sound and hot gas be absorbed through the holes into the packing. And two mufflers is going to be quieter than a muffler and a resonator, because the total absorption volume is higher.

Borlas are not super quiet like a stock muffler, but they are quieter on many dB tests compared to other performance mufflers. As far as flow/dB goes, they are usually one of the top performers. In order to get significantly quieter you would need to reduce flow.

As far as the borlas, I would call the company and ask them. Which are the quietest, which are stainless packing vs fiberglass, what is multicore, etc. The ATAK are pretty loud, I think they split the flow into 4 smaller pipes and back into one large again, and they seem pretty loud. I don't think you will like the ATAK dB level, I don't like the way they sound either, too raspy for me, I like it more crisp and deep.

Also, they do offer 3" resonators in some of their kits, you might want to ask for part numbers just to check them out. But the larger volume muffler of the same size is going to be slighlty more effective. Four total mufflers definitely won't be half the noise, but it will be quieter than one muffler per side and quieter than one muffler plus resonator. It's also more expensive and more space.

Also, Greg, keep in mind if you are just cruising around at light throttle it will be relatively low volume compared to when you get on the go pedal. The go pedal will be like a volume knob with the big block, you can't contain the beast when you get on it. Just know it will get loud unless you choke it to death. But for just cruising around it can be mild.

So in a way its kind of like a built in valve, its just before the intake instead of in the exhaust like one of those valved muffler gimmick deals. An automatic flow activated exhaust valve requires some sort of backpressure to open or it would be open all the time. And if it had a light enough spring to be very high flow it would probably rattle. Reminds me of the old gravity rain blocking flappers on tractors that would open when they are running and rattle at low engine loads.

Did you know the UPS trucks run borla mufflers because they pay for themselves with fuel savings vs the stock mufflers on the big brown trucks? Next time the UPS guy is there you will probably be listening now. Although the turbo between the diesel and the muffler helps too. Maybe thats the solution Greg. Twin turbos would definitely help quiet it down!
 
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OK....

Here's a quick revision of the previous list. I added some extra details and highlighted some particularly noteworthy items in either red (bad) or green (good)...

The objective on this one was to start trying to compare the mufflers based on how much case volume (displacement not noise) each one has, since it appears that maximizing this attribute is where you're going to get quietness more than almost anything else. The list is sorted from the largest value to the smallest (volume in in^3)


MufflerSort.jpg



A couple of noteworthy items popped out of this analysis.

  • If the MagnaFlow is considered to be a "Good" flowing muffler, than it appears to offer good value for money.
  • The Walker QuietFlow3 would have been a stellar choice for getting a large case volume, but they appear to be too restrictive and will kill power.
  • The Borla Multicore option is a crap-ton of money but in a relatively small space. However, if there is some "magic" that allows the 4-core internal design to create quietness in the small package, this could be forgiven
  • Using "Race Bullets" as resonators seems to be a waste of time.... they are inexpensive, but also offer almost no case volume... so they are unlikely to quiet down the exhaust in any meaningful way.


-G
 
I personally only run magnaflows. They're aren't the quietest of what's out there. But they offer a good sound and reasonable price. Seems to hold up very well and are a straight through design
 
I ran a very large case magnaflow on my k5 and it was very quiet, 3 inch and I think mine was offset inlet, but you couldnt hear the exhaust over the tires at cruise. Had a nice tone but idling it was very very quiet(exterior) you could hear the engine because of the intake noise.. which is why I am not using it in my blazer now.
Ill get some measurements to see if its what you already have on the list.
 
I have run the bullet mufflers on quite a few things.
They don't quiet much...
 
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