TORN

iTrader: (17)

So I got a 421 ci motor.

I know its making north of 500 HP (never ran on dyno) but some day I will confirm. Tuning is coming along and its getting more and more fun to drive. So here's my question to the people in my neck of the woods CI wise, did you move to 4 inch sigle exhaust and have regets? As in was it too loud? I am not looking for Max numbers but I want a good sound but not red neck no muffler sound. I hear the videos on you tube and many are a touch to loud for my taste. I am running Hooker long tubes into 2.5 pipes into a 3 inch magnaflow cat back atm but I want to go bigger.

I know, I know can't have big and not loud.

I am looking at running the 2.5 off the long tubes into a 4 inch collector and all the way back single in single out muffler. Looking at Hawks setup specically and pick out my own muffler to suit my needs.

I am not against loud at WOT just don't want highway drone and upset neighbors when I fire this beast up. Moving out of town soon so I can fix the second part myself lol.

Orr89RocZ

iTrader: (20)

Whats the compression?
What cam?

I had a 4" on my 383 with a 6" case ultraflo round muffler. It was very loud lol only way to keep it relatively quiet is to add a few mufflers. One bullet in the I pipe region, and then a big one in the stock muffler location.

TORN

iTrader: (17)

Mike Jones custom cam:
Intake lift: .582
Exhaust lift: .589

Duration:
intake: 240
Exhaust: 242

110 centerline

I am not totally sure of compression but memory says north of 10 to 1 but not by much. I run it on 93 octane with no problems

Orr89RocZ

iTrader: (20)

Yeah it will be abit loud but it will depend on the muffler. A big truck muffler may do it

paulo57509

Totally off-topic, but when ever I see "421 ci" I automatically think Pontiac Super Duty. Like this:

midias

If you like your magnaflow I would get this one 4" in dual 3" out magnaflow muffler. I have heard them they are not crazy loud and sound really good. You can also add a 4"

https://www.summitracing.com/parts/mpe-12594/overview/


You can also add a 4" bullet like this one after the merger to quiet it a little more


https://www.summitracing.com/parts/wlk-24217/overview/

TORN

iTrader: (17)

Midias that's a great idea, I never thought to use 1 into 2 to help with noise. Anyone got any pics? I want to see how well it fits.

midias

I think the best bet would be to measure the stock magnaflow and see how it compares to the dimensions listed. See if you think it will fit. Might look similar tot he old SLP exhaust systems


Case Exterior Length (in.): 22.000 in.

Overall Length (in): 28.000 in.

Thickness (in): 5.000 in.

Width (in): 11.000 in.

skinny z

Based on that statement alone, have you considered Holley's dual 2.5" system?
At 4" vs 2 x 2.5" you have about 80% less cross sectional area but at almost 10 sq/in (2 x 2.5") that may be more than enough to support your estimated 500 HP. The easier part is in the choice of muffler. 500 HP needs more than 1000 CFM before the exhaust starts to erode output. And 1000 CFM mufflers are rarely on the quiet side. Two 500 CFM mufflers on the other hand, can easily be found in just about any style/shape/ sound that you need.

TORN

iTrader: (17)

I know the magnaflow 14153 is a popular 4 inch muffler and it is much smaller

Overall Length (in): 20.000 in.
Thickness (in): 5.000 in.
Width (in): 8.000 in.

TORN

iTrader: (17)

Yes skinny Z I have but $800 and the fact I will have to rebuild my y pipe is why I am looking at 4 inch single. I can use my already built Y pipe with the 4 inch single from Hawks is $450 add $200 for mufflers and I can save alot of money. I wish they would hurry and release a steel version.

Orr89RocZ

iTrader: (20)

Spintech makes a 4" inlet dual 3" out like stock crossflow style i believe

skinny z

Understood. I'd like to see a steel version myself.

25thannivZ28

When I put my 406 in, I kept my 3" Flowmaster exhaust on, my SLP Shorties w/ 1-5/8" primaries.

Ran between 12.9 & 13.1 @ around 106. I had 308 rwhp. I thought it was weak, then I invested in the Hooker LT Headers, 1-3/4" Primaries, 3" collectors into the single 4" Magnaflow muffler. Similar cam, now run 437 rwhp & 11.9 @ 117.

I'm not sure I didn't catch your Carb size (or TB capacity) relative to CFM. I've got 850, I should probably go a bit more.

I went with 4" because its unique, I've gotten several compliments on it. On how it sounds and how it looks. Though I've had some people wonder "WHY ONLY THE SINGLE EXHAUST, I WOULD HAVE GONE TRUE DUALS"

Well, that's their preference, I really don't care. I have absolutely no regrets.

Its got an awesome idle, I've never heard the WOT because I've never been behind it to know if its too loud. I recommend it!

TORN

iTrader: (17)

Are you running the magnaflow muffler part number I posted?

TORN

iTrader: (17)

My throttle body is in the 850 CFM flow range. I had a bigger 1050 CFM TB and just put the smaller one back on to fix some tip in issues I was having. No fun with a stick car.

25thannivZ28

I don't know the individual part number of my muffler that came wth my kit. But it is a single-in-single out 4" Magnaflow. See straight through it.

This is the kit I have...

https://www.mufflex-performance.com/...lowmaster.html

25thannivZ28

Wouldn't hurt to plug the 1050 back in if you got the 4". I'm tempted to get a Dominator 1050 or something of the sort to see if I find any gains (or lose streetability)

skinny z

Very significant improvement. How similar a cam though? The exhaust upgrades are on my radar and I expect an increase about half of what you've posted.

25thannivZ28

Ok, i guess not extremely similar, but ive got..

Intake lift: .565 with 1.5
Exhaust lift: .580 with 1.5

Duration:
intake: 247
Exhaust: 253

110 centerline

25thannivZ28

I think a key to my improvement was the headers. Shorties with 1-5/8 primaries were good for my 350 but a bit small for the 406 and AFR 1054 heads. 1-3/4 Hooker LTs probably a huge increase

QwkTrip

iTrader: (22)

4" exhaust is loud. Real loud.

3.5" exhaust is more than adequate for your power level. Hawks (Stainless Works) sells 3.5" kits and it fits very well. I bought mine with a hidden turndown tailpipe because showing exhaust under the bumper is sooooo 1980's.

skinny z

Absolutely. An engine has to breath. As an example, back to back testing at the track showed that with my mid 12 second 355, uncapping the muffler (I've a cut out placed right at the turn before the muffler) in the 1/8 mile, there was a 1 1/2 MPH improvement in trap speed. No tuning or other changes. That says something there. (Mostly that my muffler is a total cork)

skinny z

Hmm. That might be an alternative for me.
As for the hidden tailpipe, I had to rotate my exhaust tip down to make room for the trailer hitch (yes, a trailer hitch). After the hitch was removed, the tailpipe was more or less frozen in the turned down position. That's why my racing buddy nicknamed my car "the leaf blower". (and it's true).
That's the one thing about the BlackHeart arrangement I don't care for. The exhaust tips.

midias

Just for reference the magnaflow muffler on the kit for our cars is

MagnaFlow 16829 has a muffler that is 5 in. x 8 in. x 18 in.

1badmaro

4" is not that loud cruising but WOT is. my 355 with afr 1054 big solid roller and just under 11-1 comp hooker super comps with a mufflex Ypipe 3" to 4" and a maganaflow muffler https://www.youtube.com/watch?v=oTDO0vNQjMM https://www.youtube.com/watch?v=Rs182oyqM0o