Well I am trying to deceide if i should spend the extra dough on the mufflex 4" exhaust. What do u guys think? Here is my engine set-up:

406ci
10.5 compression
AFR 195cc heads
solid roller cam 242/248 5.71/.577 @ 0.50
Hooker LT's
T-56
12-bolt with 4.10's

In the very close future i am going to put a 150/175 shot of nitrous on it. Is the 4" going to be worth is to me? Or should i get one of the better 3" kits like that one that says it flows with-in 99.9% of a straight pipe? The car is a week-end car with some track duty too. But just for fun. thank you


Shawn

Edit the 99.9% cat-back I am talking about is the STR one.

 

spend the extra dough and get the 4".

 

A good 3" will be fine.

 

properly done dual 3" will do it IMO

 

A single mandrel bent 3" system with a mufflex or equivelent y pipe and a straight thru free flowing muffler is all he needs. I have a similar set up to him only a 383 and a slightly larger cam. I use a mufflex y pipe with a single bullet in the intermediate pipe then the axel pipe and tail pipe. I pick up only 1 mph going open exhaust.I also originally had this motor in a 1980 z28 with dual 3" and an x pipe and went the same as this current firebird with open exhaust.

 

What kind of fwhp do you think the car is going to make?

 

A strong 406 needs a 4" exhaust - no 3" is gonna cut it. If you want to save $ and weight, you can go with a 3-1/2".

 

My question is how much are we talking to lose? I mean is it 8hp or 40? I know the ATR is one of the best 3" cat-backs out there. The car may be a weekend car but i don't want it to be over the top in terms of loudness.

 

I used to think the same way until I actually took my car to the track and found out it was still very close to my old car with the dual 3" system. If I can run hi 11's @ almost 120 thru a single 3" pipe so can he.Its all in the y pipe and muffler.

 

well i love my 4 inch mufflex with a spintech muffler... i have a mild 355 dont know hp numbers but flow's great and sounds awsome

 

I have a similar setup as you and went with the 4" mufflex kit with dual tip spintech muffler. You will not be dissapointed. Please don't believe the 3" single pipe is good enough for a 406 and nitrous. With my old 350 it went 8.52 through the 3" kit and when I uncapped it the car went 8.06. Backed this up twice. The 3" kit on my car wasn't even optimum for the 350 much less the 406. I went 6.95@100.82mph with my 406 and a 125 shot on dot tires and through the mufflex exhaust. I don't have as much cam or gear as you either. These are 1/8th mile times. This is actual experience not just an opinion.

 

Yea this seems to be a very divided topic, my next question is: I smufflex the only company that makes 4" exhausts for our cars?

 

Its not the 3" pipe that was holding you back . Most likely it was the muffler. I picked up about .3 taking off my flowmaster and putting on the bullet.

Yes I think mufflex is only company with a 4"system.

Mine too.

 

I was looking at the magnaflow cat-back with the single in dual outs on one end muffler and one tail-pipe loops around. Do you think that will be a pretty good muffler?

 

I believe thats the muffler that TRAXION had on his old iroc and it worked very well. I think he was running 11.6@117 on street tires.Its advertised as a straight thru muffler so I think it would work out real good. I was even thinking of giving it a try.

 

I too had the flowmaster. I agree that some must have been the muffler because flowmaster just doesn't flow. Bottom line is that if he has a 406 and nitrous the 3" just won't let all of the potential power be unleashed. He definitely won't get hurt by getting 4". On the other hand if he does go ahead and get the 3" system and it doesn't perform as expected then disappointment will set in and he will eventually upgrade to a 4" system. Why not just do it right the first time and be done with it?

 

I agree that a 4" system would work for him , but the mufflers that come woth the kit are still chambered.There was a thread a long while back about this topic and one of the posters had a 600+ hp motor that dyno'd better with a single 3" borla system than the 4" mufflex system. I think with a straight thru 4" muffler it would have been different, but also annoyingly loud since the only 4" straight thru desing mufflers I've seen are race only and don't really do much muffling.

 

Yes I have been talking to someone on camaroz28.com and is running the magnaflow cat-back and a cut-out. He said he gained no RWHP with the cut-out open. His car dynoed 574 RWHP BTW.

 

3" dual or 4", it's not going to be a very noticeable difference. In fact, too little backpressure *may* effect power. The engine's power is from heat. Not fire, not gasoline, not oxygen, not an explosion (because it burns, it doesn't explode).. Heat. A certain level of backpressure is actually good because it helps keep heat in the combustion chamber. I'm not saying 4" is going to be overkill, but in a 406 it's not going to be a token either.

 

AHHHH! BACKPRESSURE IS ALWAYS BAD!!!!! what your thinking of is scavaging. scavaging helps pull the air out of the cylindar, and increases velocity.

 

I just wat to point out that at tracks like Englishtown that monitor noise (on certiain days), they look under your car. If the muffler is chambered, you race, if its a bullet type or glasspacks, you don't race.

 

The magnaflow is not a bullet or glaspack type of muffler

 

except it looks like one...


go with the 4"....