Got some SFC welded on today, since I was at muffler shop, asked about upgrading my well-flowing (awesome really), yet ugly as hell cat back area.

I have no cats, and what was there was the SLP LT, SLP ORY, then reduced to 2.5 back to a Hooker muffler, and huge exits out the back. Crooked and muffler + exits very visible from back end.....

So, had some mandrel bent 3" put on the Y-pipe, and, 3" into a Flowmaster 80 series , with 2.5" exits, turndown just barely after bumper, slash cut chrome tips. Looks awesome, sounds quieter (old setup was loud as hell), BUT I swear to hell, I have shittier flow. I think that, based on when I put it to the floor, I was wondering where the kick in the face pull went.... it felt like it was choked.

Should I ... get cutout ? Hooker muffler back (a single in/single out), or ... ?

I am very surprised at the difference I feel in driving the car, it just feels like it is choked now.

Chewie

 

Switch back to the Hooker. No sense in putting in a cut out if you are going to want to leave it open all the time.

 

Update : Muffler was a single in/single out Hooker. Don't know the model. Pipes (ORY was and still is 3") were 2 3/4" in, and 2 3/4 " out. After the exit, a Y of same diameter was welded in, and both pipes had huge , like 4" tips. It flowed so much, when I got off it after a hard run, I heard the air stop flowing as much, if that makes sense.. (cup your hands up to your mouth, then give a sharp deep inhale.. is appx what it sounded like backing off throttle after hard run of WOT up to 125 in OD.

What there is now, after the ORY : 3" mandrel bent back to the Flowmaster Series 80, with 3" in and 2 x 2 1/2" outs. And it is solid, good looking work. Sounds alot cleaner, herein lies the rub, I felt a definite loss of power on the way home.

That being said I have spoken to the shop, talked to the guy that did most of the work, and he is willing to work with me somewhat, but, he thinks the problem is now I have TOO MUCH flow, and I have lost some bottom end (the power loss I feel). He has been doing this for years, and says as far as what I had VS what is on the car now, that there is no way the 3" setup with the flowmaster is flowing LESS than the 2 3/4 homebrew with the Hooker.

I am inclined to beleive him, should I not be so ?

To that end, he recommends against putting in cutouts (even less restrictive).

I drove home in traffic, so I have not been able to verify if the issue is more of a powerband shift, that maybe could be tuned (thinking there was a torque shift towards top end)

He is willing to work with me, but at this point I don't know what I should ask to be done ? I need some expertise here. Could it even be the tune not working with new flow setup ? My ideas to ask for are :

Get old Hooker rehung, somehow (yeah even I am lol'ing at how that sounds)
Different single in/dual out muffler
Different Single in/Single out muffler
Cutouts

Apologies for such a long drawn out post, I did do some research first, but not directly on the Flowmaster series 80, and I never thought going from 2 3/4" to 3" after the ORY, would be a problem.

Looking for some tech advice here, please spare me the "LOLZ NEWB BLOWmaster suxx". I read those, I get it that some dont like them, I also get it, that some only lose 8hp and 9tq from the FM to a cutout.

So confused.

Chewie

 

I would recommend putting your old muffler back on. From what we have seen on the dyno the flowmaster mufflers are typically not much better then stock. They sound pretty nice but don't do so well on performance. I don't think you have too much flow, these cars don't require as much back pressure to make good power. We have had some pretty good numbers from hooker cat backs so that would be they I would recommend going.

 

That is an option. It really did look like hell though. So, would you say keep 3" pipe, go into the Hooker, and, I guess I could have him try to hang and use the pipes and tips that were done up for the Flowmaster ?

I made some edits to posts above with more accurate info. I'd like to invite further responses please. This car is a daily driver, with plans to take it to the strip in the future, if that is pointless to what I am asking about, please disregard.

I did read that, no matter what, a single in, single out, will always outflow a single in dual out ? Is that truth ? Or, is there a single in/dual out that is actually awesome. I could bargain for that as well.

Chewie

 

Solved. The muffler was a Hooker Maxflow. Just talked to previous owner. He says go get your old parts come see me, and he'll weld it back.

Chewie

 

screw the bs!!!

put a bullet muffler on back of y-pipe, turndown on back of bullet.

minus 25 lbs for catback, no more tips, and nice loud sound

 

Damn it, I hate people at muffler shops. His answer sounds just like all the f#%king "advice" that I have ever recieved at a muffler shop reguarding my exhaust. "3 inch is too big." Thats all they ever want to tell you. They flip **** when you tell them about the mass produced true dual 3" kits, or the 4" kits. "Oh but you need back pressure. Those headers of yours with 1 3/4 primaries are killing your performance." And thus starts my speech about how this game isnt the same game played with their 350s that they have been welding up 2.5" exhausts for, for the last 30 years... and btw just because its a 5.7 doesnt mean its a 350... sorry. I tend to get a little pissed off when muffler people tell me that 3" exhaust is too much in reference to my car. LS What? Aluminum? 346? Dude, look at EVERY cat back kit for our cars. They all (to my knowledge) use at least 3" pipes. Some use 3.5" and one uses 4". Corvettes do use mainly 2.5" kits (although plenty of manufactures make 3") but they are TRUE DUAL. So no, the 3" isnt the problem. Its the muffler. Flowmasters are KNOWN for their inability to flow for LS1s. Keep the pipe, get a different muffler. Do not listen to the advice of muffler shops unless they custom build LS1 exhausts. If he doesnt know what cubic inch and LS1 is, then he doesnt know anything about the gen III world, and therefore everything else out of his mouth is based on traditional small block practices. Thousands of $ have been invested in finding the optimum size tubing for our cars, and 2.5 inch or 2.75 inch piping wasnt found to be optimal for anything but stock cars. To my knowledge the SLP 2OTL that came on the early SS's actually has a 3.5" inlet on the muffler FYI (cant remember the source of that info though). Hope this helps.

 

Helps alot actually. Prev owner basically broke it down the way you did as well. Turns out he is a welder (that part I knew), and specializes in making custom tuned exhausts. Built headers for his pops autox car. He says "Dude, I TOLD you to call me when you wanted to do up the exhaust." He knew it was ugly, he just did it up for personal use, and wasn't ready to sell, I came up with $$$ fast, and so on and on.....

Too much time in town, on the city streets, to do bullet(s) and a turndown, imho. I asked him if he could do just that (keep the new 3" and use the Hooker Maxflow that was on it. He looked at me like I asked him if he could tie his shoes.

I have zero complaints about the workmanship or any complaints at all about the Meineke place. I could have (should have) known better and said "no, use the muffler thats on it". Since he is selling a restored Chevelle, and a Cuda (340in), 100% agree with your analysis of how he ended up reccomending the Flowmaster.

I would even do a dyno before and after (FM series 80 vs Hooker Maximum Flow) except only dyno I know of in Rockledge is at a place where owner charges 100 bucks for 1 hr, and u get as many pulls as you get.

I am interested in the hard data, just to see it, but cannot afford 100x2 just to find out. If anyone is in Brevard County, or close, and is interested in subsidizing (meeting me 1/2 way ? on $$), OR you can offer better for a before and after, shoot me a PM. I think it would make a great example. Alot of Fbodys out there, exactly like mine. (See mods in sig) Should be able to do same day, will verify with welder.

Thanks for all the info,

Chewie

 

just get the other one installed. flowmaster is a proven bottleneck

 

yea get your old one back. the maxflows flow just as much as a straight piece of pipe. the 80 series for our cars is like installing a 1/2" piece of tubing back there.

 

do you have any 1/4 times to use as comparison? i had a bolt-on a4 z28 that trapped 109-110 in the 1/4, it had headers, true duals, x and magnaflow 4x9 mufflers. it had a noticeable pull and felt good. my wife bought a 99 ws6 that had a flowmaster muffler on it. we put a lid on it and drove it around for awhile and it felt dead compared to my bolt-on car. took them both to the track and they both trapped 109 haha. her car was much quieter, but for some reason felt much slower...when in reality it was not.

sound has a lot to do with how a car "feels" in terms of performance. same can be said for my buddy's bolt-on 01 z28. car "felt" good with headers, long tubes, x and dumped duals. he then put an ory and stock catback on it because he wanted to quiet it down. car trapped the same. went 108 no matter what.