mufflers or no mufflers??

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silentj95835

6Valiant6
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I have a 66 valiant that has a rebuilt 360 motor. mild upgrades.I finally got it tuned by a shop and they are telling me I need to open the exhaust up and see if this is causing my performance issues. They checked everything on the motor to make sure it was correct. timing, tdc, timing chain, valves,compression, coil bind, etc... cost me $400 for them to tell me everthing is fine and they cannot figure out the loss of power other than it could be that im S.O.L because I cant put a set of headers on here because of the early A-body unless I re-cut my fenders out again and put headers on or its my msd box. Im going to send my msd in for inspection but im curious about opening up the exhaust. when i got the car running I had the pipes on, no mufflers because I didnt have my welder. It performed really well. After I put the mufflers and new 2 1/2 pipe on my performance decreased. I am running 2 1/2 piping from the factory manifolds to 2 flowmaster delta 40's which exit right b4 the rear axle w/turn downs. I was wondering what is to be gained or could be damaged by having the exhaust shop cut my exhaust off and have 2 1/2 or 3 inch pipe from the manifolds and exit by the front or rear tires with no mufflers. i know its going to be a loud S.O.B but im running out of options. any opinions, criticisms, alternatives would be greatly appreciated. thanks for taking the time to read my long post.
 
Im no expert mechanic by far, but I do know that your current exhaust system sounds pretty good flo wise. 2 1/2" pipe would be ample for a mild 360 I would think, & 40 series mufflers flo descent as well. Not the best flowing muffler in the world, but they are the only thing I will ever run, good flow or not.
Could be your cam. What cam are you running? Some cams dont work well with restrictive manafolds.

The only thing that I can think of that would be bad about running straight pipe is
1: the noise & you already know that.
2: old timers will tell you that running straight pipes will burn up valves over time.

Other guys that know alot more than me will chime in, so be patient.

Welcome to the site!! You will like it here.
 
ah, i unfortunatly dont have an answer from you, but seeing as its your first post, you should introduce yourself in the Welcome Wagon forum, post some pics of your ride or somethin. anyways, welcome!
 
Silent;

First up, welcome aboard.

Next up, would you list the mild upgrades? The reason is, mild has so many levels. Other than that, from reading what you wrote, I'm puzzled. An open exhaust will make max power, but a 2-1/2 pipe should be good for a decently powered engine. A loss in power due to your system should be small unless your engine is a monster 500+ mill.

I don't understand where this loss is so bad.
 
This may not help but a long time ago i herd the flowmasters restricted more airflow than some of the others on the market. It was from an exhaust shop owner. and it may have just been his opinion

anyone else ever herd that?
 
OK here is the scoop. My husband has run extensive dyno tests on his dyno using mufflers on his superstocker, my street car, and almost every engine he dynoes. How much the muffler flows means nothing. If you want flow, then take the entire exhaust system off. It is the speed at which the exhaust flows that counts. My car has stock exhaust manifolds, 38" of 2.5" pipe and supertrapp mufflers with 28 discs each. The dyno said that was optimum for my combo. It made more power over open pipes and more power over flowmaster 40 series mufflers. My engine makes power to 5500rpm and is a very mild street engine. The length of the pipe from the manifold to the muffler is a key point that is always forgotten. Your big power loss is not in the exhaust which is always easy to blame much like carbs. and ignitions. My guess is that it is a little bit of everything that is wrong. Also, open exhaust rapps up fast when you hit the throttle, but doesn't under a load. I have heard thousands of drag cars sound like prostockers in the burnout box but are terds off the line:rolleyes:.
 
flowmasters don't flow well? I was looking into gettin super 44's maybe i'll have to look into that more....what mufflers out there are considered top flowing these days? Also, if the length of the pip from teh manifold to the muffler is crucial to making the most power, what is a good length? shorter or longer?
 
6dart9 said:
This may not help but a long time ago i herd the flowmasters restricted more airflow than some of the others on the market. It was from an exhaust shop owner. and it may have just been his opinion

anyone else ever herd that?
Click to expand...

Well, they dont flow super-duper great like a spintech or an open muffler like a pro bullet but they do flow good enough! I think the best one they have on the market right now is the SUPER 44. It is supposed to out flow all of the other flowmaster mufflers....I think. One of the muffler shops in town really hates flowmasters & he will say anything about them in order for you to get magnaflows. He has even gone as far as telling the kids that flowmasters are bad for your valves. What a crock!!
 
i dont think i would ever go with magnaflows....almost every guy with a v8 around me runs magnaflows and they sound like ****...i would go either flowmaster or dynomax...my friend tells me to go borla xr-1, but i think thats a race muffler lol....if i have to sacrifice 3-5 horsepower for a good sound i dont mind, but anything more than that and im concerned
 
Flow numbers for mufflers is one of the most useless specs out there. All of the performance mufflers flow more than anything but the biggest IHRA prostock mount motors can flow.

As others have stated it is much more important to have the right size pipes and lengths in front of the motor that what muffler is there.

Some time back I read an SAE paper on designing zero loss exhaust systems, that is the motor will make as much power with a full exhaust as it does with open headers.

The interesting thing I took away from that article was that it is easier to design a zero loss system with a chambered muffler than it is with a straight through absorbtion muffler like a magnaflow or ultra flow. The article stated that with the chambered muffler once the exhaust entered the muffler the rest of the system appeared to the engien as though it wasn't there and the the absorbtion type the rest of the exhaust past the muffler appeared as a restriction.
 
mshred said:
i dont think i would ever go with magnaflows....almost every guy with a v8 around me runs magnaflows and they sound like ****...i would go either flowmaster or dynomax...my friend tells me to go borla xr-1, but i think thats a race muffler lol....if i have to sacrifice 3-5 horsepower for a good sound i dont mind, but anything more than that and im concerned
Click to expand...

X2... When they first came out I had a pair put on my 71 F-100 w/a 302. They sounded like a good turbo muffler when new, but now they just sound like burned up glasspacks!
 
mshred said:
i dont think i would ever go with magnaflows....almost every guy with a v8 around me runs magnaflows and they sound like ****...i would go either flowmaster or dynomax...my friend tells me to go borla xr-1, but i think thats a race muffler lol....if i have to sacrifice 3-5 horsepower for a good sound i dont mind, but anything more than that and im concerned
Click to expand...


I run flows because that was on it when I bought it. LOL!

My neighbor was barking about his Magnaflows and how good they are. I stood there and didn't say anything except that I had flows on my car. His car sounds like a slant six when it goes by my house! Its a supercharged thunderbird 302! You wouldn't think it has a V8 in it but it really dose. It has the X-pipe and the whole nine. After hearing that car I will never have a Magnaflow on anything I own.
 
yup...every guy around me with a v8 all run the same exhaust being magnaflow....one guy even tried to tell me flowmaster is **** and that magnaflow outflows them...If my eyes were closed when he started up his firebirn for i swear i would have thought it was a chevy beretta with a whole in the exhaust....the only thing i have ever heard magnaflows sound decent on is some imports like 350z's, but they only sound good because they enhance the import fart sound...ill never go maganflow...sorry mario andretti
 
mshred said:
yup...every guy around me with a v8 all run the same exhaust being magnaflow....one guy even tried to tell me flowmaster is **** and that magnaflow outflows them...If my eyes were closed when he started up his firebirn for i swear i would have thought it was a chevy beretta with a whole in the exhaust....the only thing i have ever heard magnaflows sound decent on is some imports like 350z's, but they only sound good because they enhance the import fart sound...ill never go maganflow...sorry mario andretti
Click to expand...

LOL!

It really does sound like a big a** hole in a exhaust pipe!
 
My69Barracuda said:
OK here is the scoop. My husband has run extensive dyno tests on his dyno using mufflers on his superstocker, my street car, and almost every engine he dynoes. How much the muffler flows means nothing. If you want flow, then take the entire exhaust system off. It is the speed at which the exhaust flows that counts. My car has stock exhaust manifolds, 38" of 2.5" pipe and supertrapp mufflers with 28 discs each. The dyno said that was optimum for my combo. It made more power over open pipes and more power over flowmaster 40 series mufflers. My engine makes power to 5500rpm and is a very mild street engine. The length of the pipe from the manifold to the muffler is a key point that is always forgotten. Your big power loss is not in the exhaust which is always easy to blame much like carbs. and ignitions. My guess is that it is a little bit of everything that is wrong. Also, open exhaust rapps up fast when you hit the throttle, but doesn't under a load. I have heard thousands of drag cars sound like prostockers in the burnout box but are terds off the line:rolleyes:.
Click to expand...


Excellent!!!!!!!! I couldn't have said it better.

dgc333 said:
Flow numbers for mufflers is one of the most useless specs out there. All of the performance mufflers flow more than anything but the biggest IHRA prostock mount motors can flow.

As others have stated it is much more important to have the right size pipes and lengths in front of the motor that what muffler is there.

Some time back I read an SAE paper on designing zero loss exhaust systems, that is the motor will make as much power with a full exhaust as it does with open headers.

The interesting thing I took away from that article was that it is easier to design a zero loss system with a chambered muffler than it is with a straight through absorbtion muffler like a magnaflow or ultra flow. The article stated that with the chambered muffler once the exhaust entered the muffler the rest of the system appeared to the engien as though it wasn't there and the the absorbtion type the rest of the exhaust past the muffler appeared as a restriction.
Click to expand...

Great article. I've read a few write ups and a well designed exhaust isn't just a simple set of pipes.

On street cars, the exhaust system is an overated issue were the most power is lost due to poor design and build. (Leaks, poor weld, etc..)
 
When you installed the new exhaust, did you MIG/TIG/STICK weld at all? If you did, did you disconnect your MSD ignition box?

if not, your MSD box may be damaged. All aftermarket ignition boxes should be disconnected before any electrical welding is done.
 
Unless I missed something I don't see an "X" or "H" pipe mentioned here. The scavenging effect from this will fill in the low end like crazy on a street car as well!
 
In 1989 my uncle returned home after working in California for sometime. He drove his only car since highschool, a 1967 El Camino with a 283. He had Flowmaster mufflers on it which he bought one night at a dirt track race swap-meet. The guy that sold them to him a couple of years befor he returned home, was the founder, Ray Fuller (I think thats his name).. Keep in mind this was 89 & glasspacks were still the big ticket around here. He had the first pair of flowmaster mufflers in town & probably in Oklahoma to boot! People always stopped & asked him what he had done to it to make it sound like it did!
 
thanks for all the replies and info. I dont know why it says my first post because i have had several posts just not in the last 2 months. but ne ways hi to everyone.i have str8 pipes to the muffler on each side right before the rear axle. no x pipe.
100_0167.jpg

parts on the motor:
kb 10:5:1 pistons
balanced motor
melling high flow oil pump
mild port on the heads
roller rockers 1:5 ratio
all new valves etc..
ported elderbrock manifold
demon 750 double pumpr
erson cam 510 lift
solid lifter setup
stock manifolds
electric 112gph fuel pump w 5/8 lines
msd 6al w/pro billet magnetic distributor
 
the muffler shop did the exhaust system and no they did not disconnect the msd or battery. the poor performance has been there since day one. just with no mufflers and 4 ft of piping from the manifolds the car seemed way faster. once the exhuast was re-done it performed worse. the car wont rev out past 5k with the mufflers off i was able to rev to 5800 before it felt flat and that was before i paid someone to re-inspect everything i put together. after the tuning at a shop and switching out to a 8k rpm pill it revs to 6k no load but then when i drive it down the street it cuts out like the rev limiter cuts in at 5k. the shop said open the exhuast up and see if that helps. before i hack up my exhaust i want opinions on if pipe right off the manifold is a bad idea since i cannot run headers without cutting my fender well holes back open.
 
could it possibly be a fuel feed problem- I know befor I redid my car I was ginving a old skool guy a ride and it kind of "hit a wall" in the higher RPMs and he asked if I put bigger fuel lines when I changed to a V8- he said thats what it felt like to him. just another option?
 
Those look like the early 273-318 manifolds. I'm far from an expert but I think those are just to small to flow well at anything over 5000 on a 360 size motor.
I had a 383 rr motor in a cuda with C-body manifolds and it was a turd above 4500 but when i put headers on it would pull hard right past 6000. dosent tti make headers for the early "A"s now. I know there pricy but u spent half of a set on a glorified tune up and got nowhere. Just 1 opinion.
 
Silent,

What do your plugs look like? Are you running rich or lean? I have my theories on each, but lets take a look first.
 
Here are my thoughts.

510 lift cam with 273-318 manifolds. Not good,will run out of breath quick.

Was the cam degreed?

Like the flowmaster's.....Straight exhaust,Not good.

5/16" fuel line....3/8" would be much better.

MSD boxes can be as much a headache as they are worth.
Factory Mopar Performance electronic ignition works fine for a street car.
 
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