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Flowmaster single 3" in place of factory dual exhaust?

AJMBLAZER

AJMBLAZER

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So anyone replaced their factory dual exhaust on their K5 (70's, 80's diesel, whatever) with the Flowmaster 3" single exhaust setup meant for the 87-91 TBI trucks?

http://www.summitracing.com/parts/FLO-17161/?rtype=10

Starting to think that rather than making the rusty compromise I have in a box work on my truck I should just start over. Lesson learned. I can have that for $216 shipped and then either a new Y pipe, maybe reuse the rusty Y pipe I have, or maybe if I find a decent shop have them make one of the Y pipes some folks on here have run where the pipes go back to behind the T-case and then join there.

Just wondering if the Flowmaster exhaust "bolts on" to our dual exhaust equipped trucks? Hangars line up and the like. Not much in the way of performance/exhaust fabricating shops here so I'm kind left with the "do it myself" setup and then only having a shop fab a piece to go where the cat would go on a gasser.
 
You dont have just a regular muffler place around?? Here in clinton Iowa (pop. 40,000) we have like 6 or 7. Any one of them will custom bend up a true dual exhaust for under $300. I'm sure single is probably cheaper. I wouldnt see any problem in doing what your saying though. Just curios, but is that the preferred sound that you want? Or is it for space constraints.
 
1 - a well designed single 3" will outflow a dual 2.5" every day, use less pipe, weigh less, and yes, look better. Duals belong on muscle cars. Besides, if I wanted duals I could buy a mandrel bent kit out of JCWhitney or Summit for under $300 and it'd bolt right in place of my factory setup.

2 - There are plenty of muffler places around. Finding one that knows what mandrel bending is and true custom fab work from a hole in the ground...not so much luck so far. If I do find a place like that I will probably go that route.

3 - if I can't find a custom place I can piece together 90% of what I need rather easily using the Flowmaster setup and a Walker Y pipe. Just need a few feet of 3" pipe.
 
I didnt realize that a 3" would out flow 2 2.5"s. Is that why the new trucks do it that way? I figured it was a sound level thing. :dunno:
dosent make sense really though? 3" cross section area 7.065" and 2 2.5" cross section area 9.8125". 28% increase in diameter.
 
More surface area on the dual pipes. More friction/drag. Been proven time in and time out.
 
Oh, I guess that makes sense. I just like the sound of duals I guess.:rolleyes:
I knew diesels always go single but never knew why.
 
Everything's gone single now. Easier and cheaper to make. Duals are just cosmetic unless you have a mother thumper of an engine where it doesn't matter.
 
AJMBLAZER said:
More surface area on the dual pipes. More friction/drag. Been proven time in and time out.
Click to expand...

That is true, and that does account for some drag, but the differences there are very minimal.

A 3" single or 2.5" dual setup is going to have VERY minimal effect on anything but a very high hp V8.
 
Still less crap under the truck and less complication. Also pretty sure singles have better low end torque.
 
can't you just get the factory '88+ y pipe and use the kit. probably have to fab 2 brackets on the driver side. i'll tell you though....i just put that kit with a Magnaflo cat on mine and i wish i would have been able to use a 70 series muffler....it's louder than i wanted.....cools a hell though, if i was 25 years younger :D i used to use duals with Cherry bombs till i went to a big single in the late '80s
 
Mine's a diesel. No cat.

I can use the 87-91 Y pipe and this kit to make a 3" single system...but I'd need the distance and angles of the factory cat to fill the gap between the two. My main question's if I'd need to fab up some kind of hangar mounts for this or if it works with the factory pipe hangars?

Right now mine's pretty loud. Clattery 6.2L, no interior sound deadening other than 1/8" of Rhino Liner, and dual exhaust with some kind of cheapie turbo mufflers.

You have me thinking about what to fill that gap with...maybe a Cherry Bomb to act as a resonator...Hrmmmmmmm...:thinking:
 
AJMBLAZER said:
Still less crap under the truck and less complication. Also pretty sure singles have better low end torque.
Click to expand...


No the dual setup has better low end torque because of the smaller pipe size valocity, (I knew that but just looked up some test results to back it up before posting) and as my 6.2 will not spin up there I don't need big flow numbers so i will stick with old school duals.
The sound is just better to me (seperation of inpulses) verses the drone of singles. the reason for the singles on new trucks has more to do with a single turbo outlet I think. (yea and weight)
 
AJMBLAZER said:
Mine's a diesel. No cat.

I can use the 87-91 Y pipe and this kit to make a 3" single system...but I'd need the distance and angles of the factory cat to fill the gap between the two. My main question's if I'd need to fab up some kind of hangar mounts for this or if it works with the factory pipe hangars?

Right now mine's pretty loud. Clattery 6.2L, no interior sound deadening other than 1/8" of Rhino Liner, and dual exhaust with some kind of cheapie turbo mufflers.

You have me thinking about what to fill that gap with...maybe a Cherry Bomb to act as a resonator...Hrmmmmmmm...:thinking:
Click to expand...

here's the spec on the direct fit cat, for length......have a shop expand one side of a pice of pipe to slip over the y-pipe....i don't know about the hangers, but i can take some pics of mine if it would help you.

http://www.magnaflow.com/02catalyti...irectfit01.asp?catalogid=3113&directfit=93476
 
Hrmmmm...so it's straight? The Walker catalog looks like it's got an angle on each end. In that case...easy!

Thanks man. Pics of the hangars and stuff would be good. I could at least see what is or isn't there.
 
Yeup the factory cat had angles on it, but the diesel didn't come out with cats, why put one on? If you wanna fill the gap, use some pipe, or like you said earlier, some sort of glasspack as a resonator. Cat's for gas engines are different than diesels, plus if your's isn't running real clean it will clog up in no time.
 
Who said anything about running a cat?

I just wanted to know a little bit about the dimensions and angles of the cat so that I had a better idea what the piece of pipe I'd need would have to be shaped like.
 
ok...i didn't know what the origional cat looked like....the garbage i ripped out was all mismatched to make a system.....factory y to 3" cat in and out necked down to 2 1/2" in/out muffler, back out with 3".....i used a straight universal cat with "add ons" on both sides to the Flowmaster system.....was a straight run for me. i'll get some pics up tomorrow.
 
Cool.

Kind of have to see what I end up with anyway. Might end up a straight run for me as well.

Thanks again.
 
On my truck I bought a exhaust kit, like this one:

http://www.summitracing.com/parts/FLO-17161/

You can search their kits here:

http://www.summitracing.com/search/Year/1991/Make/CHEVROLET/Model/BLAZER/Department/Exhaust/Section/Exhaust-Systems-Kits/Part-Type/Exhaust-Systems/?Ns=Rank|Asc

I then added the following bits to make it all work:

Clamps (2):
http://www.summitracing.com/parts/SUM-G4625/

Band clamps (4) - there are two kinds, straight and larger to smaller, so check similar products and determine what you need for where you are connecting:
http://www.summitracing.com/parts/WLK-33226/

Hangers (2):
http://www.summitracing.com/parts/SUM-630550/

I then went to my local car parts store and bought a 3" OD connector, which is about 6" long. I slid that between the end of my cat and the muffler inlet and used a band clamp. In your case, you could probably pick up a 2' long pipe from your local store and use that to replace the cat, maybe cut it down to size to make it fit.

If you end up doing something custom for the y-pipe, tbichips.com highly recommends this part:
http://www.summitracing.com/parts/FLO-Y250300/

which they describe in detail here (TBI of course, so it may not relate to diesel):
http://www.tbichips.com/truckmods.htm
 
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