Forum: I tried a search on muffler upgrades only. Seems most people change everything when they change mufflers.
I have the usual crappy stk/cheap mufflers on my 74 w/duals.
Any ideas of how much I would pick up w/better mufflers?
No Flomasters or anything real loud please! LOL


R

 

Not enough to justify the additional expense. Order a pair of reproduction stockers.

 

True Dual Muffler flow and dB comparison. These are 2.5 inch in and out. This was also Rear wheel HP on a modded LS motor. So this was like a 450 hp at the crank motor. An H or X pipe would probably knock 10 -15 db off of these numbers. My 3 inch muffler are not listed on here. They are quiet at idle and loud at WOT. No idea on the true DB

The results in HP order:

1.Flowtech Warlock (open) 374.2 hp/ 333.1 tq
2.Bassani Real Street 373.7 hp/ 333.8 tq
3.Hooker Maxflow 373.5 hp/ 333 tq
4.Borla XS 373.3 hp/ 332.6 tq
5.Magnaflow 372.8 / 332.5 tq
6.MAC 372.3 hp / 331.5 tq
7.Flowtech Afterburner 372.3 hp/ 330.1 tq
8.Hooker Aerochamber 372.1 hp/ 330.4 tq
9.Bassani 372 hp/ 333.5 tq
10.Spintech 371.6 hp/ 332.2 tq
11.Edelbrock Performer RPM 370.9 hp / 331.3 tq
12.Borla XR1 370 hp/ 334 tq
13.Flowtech Terminator 369.5 hp / 331.3 tq
14.Dynomax Ultra Flo 369.4 / 333.2 tq
15.Flowmaster 369.4 hp / 331.8 tq
16.Flowtech Warlock 366.3 hp / 325.3 tq
17.No muffs 365.2 hp / 330.1 tq

Sound Off in Quietest to Loudest (Decibels):

1.Borla XS, 80db at idle, 90db at 2,000 rpm, 110db at WOT.
2.Hooker Maxflow, 80db at idle, 90db at 2,000 rpm, 120db at WOT.
3.Magnaflow, 82db at idle, 91 at 2,000 rpm, 114db at WOT.
4.Flowmaster, 82db at idle, 93 at 2,000 rpm, 115db at WOT.
5.Flowtech Warlock, 83db at idle, 92 at 2,000 rpm, 112db at WOT.
6.Dynomax UltraFlo, 83db at idle, 94 at 2,000 rpm, 113db at WOT.
7.Borla XR1, 83db at idle, 96db at 2,000 rpm, 118db at WOT.
8.Bassani Street, 83db at idle, 96db at 2,000 rpm, 120db at WOT.
9.Edelbrock RPM, 84db at idle, 93db at 2,000 rpm, 118db at WOT.
10.Bassani Real Street, 84db at idle, 96db at 2,000 rpm, MAX. (120+db).
11.Flowtech Afterburner, 86db at idle, 94db at 2,000 rpm, 115db at WOT.
12.Flowtech Terminator, 86db at idle, 94db at 2,000 rpm, 119db at WOT.
13.Hooker Aerochamber, 87db at idle, 94db at 2,000 rpm, 114db at WOT.
14.SpinTech, 87db at idle, 97db at 2,000 rpm, 116db at WOT.
15.MAC, 87db at idle, 98db at 2,000 rpm, 119db at WOT.
16.No Muffler, 91db at idle, 103db at 2,000 rpm, MAX. (120+db).


The Hooker Maxflow made the best power while still being very quiet at idle/2000rpm, but nice and loud at WOT. The Bassani Real Street also made nice power without being too loud.

 

Geroge: I still feel that I am leaving something on the table.
My combo:
355 w/TFS heads, 218-224 HR w/1.6 RRs
650 Demon and Air Gap
Stk RHs dual 2.25" ex w/H pipe and Stk mufflers

280 rwhp
315 rwtq
I know the RHs are holding me back. I am concerned about ground clearance and fitment of LT headers.
Somehow I think that I should be making over 300 rwhp?
Where am I wrong, what am I missing?

TIA

R

 

you would be better off with stock mufflers and upgrading the exhaust in other areas. but both parts being upgraded would be best. a balance pipe i beleive gives a nicer tone, some think an x pipe makes more power but i am not totally convinced on that.

 

Yea buy some Borlas.

 

As HP rises the need for long tube headers is a must. The 218 cam timing is holding you back. Free flowing mufflers are only needed when the HP is high enough to warrant them.

 

The fact that my HP drops off at 5K tells me that something is plugged!
The HR cam has .535 in and .539 ex should move some air w/TFS heads.
Will some LT headers get me to 300 rwhp?
I'm thinking that I SHOULD have about the same HP/TQ?
Since I have 315 rwtq, should I expect the same in HP?

TIA

R

 

What intake manifold are you running?

Is the ignition system keeping up?

Have you verified full throttle linkage operation?

 

In addition to the above. 218@50 is very mild. That will act like a rev limiter because the valves are not open long enough to continue to rev higher.

 

I know my cam is "mild", I wanted BB mid range and I got it!
In looking at dyno charts for similar builds to mine, they usually rev to
peak @ 5400 rpm. I am way short of that.

On top of everything else, I have the small RHs w/smog.
I know I need to open up ex, but how and how much?

R

 

1 5/8" headers, dual 2.5 and any kind of muffler will be *more* than enough for your setup.

 

I suggest targeting the point of highest restriction. I would do a pair of cheapo muffler shop turbos. I bet it helps and would sound great. Spend a little more and get Walkers if you wish...

 

Yes, get low restriction mufflers for your duals. Headers rec.!

 

Forum: The local hot rod muffler shop guy told me $350 for 2.5" ex
and an X pipe and Magnaflows.
The condition was that the headers go straight through the cross member.
How many off the shelf headers are a straight shot through the cross member?
I'm thinking the Dynomax 1 5/8 or Hooker SC?
Suggestions please?

TIA

R

 

None of them do. that is why all the people here on the forum have these really otherwise nice systems with all these bends and contortions. That is why I concluded 20 some years ago that the guys who first created the cross member were D.S's it makes for an overcomplicated system. That is why I modded my crossM for a straight back pass under system

 

George: Since easy is not happening, what are my options and how much will it cost?


R

 

If it's a 350ci motor 300 at the wheels is not as easy as you might think. Magnaflows flow good and sound good. My old 355ci missed the 300rwhp mark by 4 ponies and it had some pretty good HP parts in it.

Holy shnit my last exhaust system cost $1500 and that is without counting the headers

If you have angle plug heads go for the Dynomax, not end of problems with the SC, Nothing off the rack goes straight through the crossmember, take it to a shop and have them do it

 

Id go with FLowMasters and an 'x' crossover put as close as possible to the engine ; the 'x' alone on mine reduced the db's especially above 2500 rpms.

 

Forum: As I see it, I can buy headers and spend the money to get them through the cross member.
Or I can do the Brezenski/ McJacks thing and get some modded up stockers that fit properly?

Any thoughts?

R