alright, i just bought a set of hooker 2460's from ACS, coated, and they are freakin' nice! i want to run shorties for maximum ground clearance. i also want the highest flowing exhaust for the car, looking at the mufflex 4". my problem is that i can not seem to find a y that has 2 1/2" in 4" out. flowmaster has the one with a 3 1/2" out but that's it. would the 3 1/2" mufflex system flow enough? i know i only have a 305, but for those who have followed my project know that i don't play around when it comes to making power. the true duals are just too loud, so this is why i want to go back to a single. keep in mind that this motor will see boost by next spring, and i would like to run on that fine line of 11.99/12.00 (don't have the equipment currently to put in a bar).

 

the 3 1/2 inch would flow plenty for a 305 actually it would flow plenty for a 350

 

My Mufflex originally was designed for a stock LS1 y-pipe, and had the reducer built in to connect the 3" y-pipe exit to the 4" intermediate pipe. However, the SLP y-pipe sucks. Too small. I custom made mine from piping I bought from Jegs. Collectors flanges are now a true 2.5" (instead of 2.25"), and merge into a 4" pipe that I bought from a local semi-truck supply store. I cut off the reducer on the intermediate pipe and connected it with a 4" flange.

Total cost of $40.

And a word of caution. If you're looking for quiet, the Flowmaster equipped Mufflex is not for you The Spintech is a good bit quieter.

 

Marc 85Z28,

I think we talked about this before but I need to make sure
about this. I will be getting the 1 3/4" SLP headers with
Y pipe, connecting to a high flow 3" converter, then to
a 3.5" Mufflex system with Spintech muffler.

To me this setup is plenty good for a modest 350hp/400 ft. lb.
350 SBC. The ONLY thing worrying me is the Y pipe. Some
guys at work are telling me "why are you even using a Y pipe?
You should go with true dual!" Y pipes will choke your motor!"
I think these guys are stupid and thick headed! Honestly,
with the right size Y pipe, I think this system can hold up
to 400+ hp if I wanted it to! My question is, will this SLP
y pipe really kill my exhaust flow badly? Should I just say
F' it and put it on and drive it when it's done? Or should I
just get a Y pipe made bigger for more flow? Can I go 3",
or is that going to kill clearance? Any help appreciated.
Thanks!

 

This is very true! BUT, if you know this guy's motor, it
flows like a freakin big block! Read his post again!
Mufflex suggests using the 3.5" on any motor with 350-390hp
or LESS. The 4" is for motors with 400hp or MORE.

If he plans on doing flat 12s, it's obvious that the 4" Mufflex
is perfect for that motor.

 

true very true i couldnt agree more sorry bout that i didnt read it all i guess ....my bad
im also used to my older cars where we ran true duals on em too...

 

The SLP y-pipe has been proven time and time again on cars well over 500HP. There have been several people with the 1 3/4" shorties, SLP y-pipe and a 3" or large catback that have gone well into the 11s, and faster. There was a full weight 89 Firebird with a healthy 383 that was running 11 flat at around 123mph on drag radials in the classifieds not too long ago. He was running SLPs.

I was just unhappy with the small size of the pipe, and the alignment problems. So I made a new one.

Many cases a true dual will work better. However a well thought out single exhaust can perform almost as well, but at a greater expense.

We have talked about this before I believe, and my mild 355 saw gains just from the Edelbrock to SLP swap, and again later with the 3" Hooker to 4" Mufflex swap. The SLPs with a 3.5" system is definately NOT overkill for a 400HP engine.

 

i know it will be loud outside the car, but it will be a lot quiter inside then with duals dumping under the car cause it's carried all the way out to the edge of the car. you guys have been a big help, i am seriously looking at the 4" system again. next stop, finding a truck supply place to get big tubing.

 

Hey no problem! Of course, if he had his original stock form
305 that was only pushing like 175hp, THEN the 3.5" or
4" exhaust would be overkill.

 

Ok, cool! Thanks for the help! You made me have no worrys now
about my exhaust set up. Since I am only hitting around 350-
360hp, then my system I listed above is plenty good for it.

One more thing, what alignment issues are you having
with the Y pipe?

 

.

 

I had this custom built for my car using SLP headers, 2-1/2 X 3-1/2
Y-pipe using a Flowmaster Y collector. It is "Noisy" but supports my setup nicely.

 

here is another pic during Fabrication.

 

And one last pic of the muffler (DynaTech Sprint car 6"L x 3-1/2" ID)

 

i bet that sounds good man

 

OMG Verrrry nice clean looking setup ......... if I don't like that SLP y pipe ..... I would definately go for this setup

 

that is nice, but looks like it would really loud inside the car, like mine is now, i want to go with something that is going to exit outside the car, not underneath it, like the mufflex does.

 

There are other round 3-1/2 ID mufflers made by Magnaflow and Walker dynomax that would fit just as well and be quieter. I may go to one of those eventually. But since the car is trailored I am in no rush.

 

Why go with a 3 inch y pipe and then a 3.5 or 4 inch catback. Pretty much pointless to do that.

 

ummm.....who said anything about a 3" y-pipe? i want to run dual 2 1/2" in/3 1/2"(or 4") out

 

would the hooker catback support enough horsepower to go 12's? i am just trying to save as much money as possible. i had some stuff come up that is going to cost some serious bucks, but i have to quiet this car down.

 

Marc 85Z28 wrote this to me:

"The SLP y-pipe has been proven time and time again on cars well over 500HP. There have been several people with the 1 3/4" shorties, SLP y-pipe and a 3" or large catback that have gone well into the 11s, and faster. There was a full weight 89 Firebird with a healthy 383 that was running 11 flat at around 123mph on drag radials in the classifieds not too long ago. He was running SLPs."


Is it "pointless" now? I DON'T THINK SO. That SLP Y pipe
only has a 2-1/4" inch diameter! It all depends on your
motor displacement, big block or small block, 100hp
or 1000hp, etc. A lot of variables. Now, for a 12 second
car, a 3" inch y pipe into a 3.5" or 4" cat back is excellent!

 

An exhaust system is only as good as it's smallest point. Having a section of 3 inch tubing run into a section of 4 inch tubing is absolutely pointless. If you had a 4 inch y pipe then the 4 inch catback would make sense, but otherwise no. All Mark's statement proved was that you can run those times with a single 3 inch pipe.

 

I used to jave the flowmaster 3in catback with the one driverside outlet and I was running low 11's all motor and touching the 9's with it....

 

really? i was just looking at this system about an hour ago, i guess that is the system i am going with! thanks for some real numbers finally!