Exhaust Sound

Marc Wulf · #1 (**permalink**) 03-02-2014, 12:37 PM

Hi all got one of pop up messages that reminded me I haven't posted in a while so why don't ask a question or something. Well here it goes.I have a 351w crate motor with what I would describe as a mild cam and not very loud side pipes.When I accelerate It sounds great! When at idle it's disappointing.What Im specifically concerned with is,there is a very distinct puffing sound coming out of one side. What if anything,could it be?

G-Pete · #2 (**permalink**) 03-02-2014, 12:52 PM

here...

Marc Wulf · #3 (**permalink**) 03-02-2014, 12:56 PM

Thanks Pete

blown871 · #4 (**permalink**) 03-02-2014, 02:18 PM

... I have about the same motor.
And I am not nuts.. but I did put in Synthetic the last time I changed the oil. (have a lot sitting the shelf for another motor that loves it) ..
The cobra the motor does NOT like it.. and it smokes. (Yes this sounds nutso.. but i will be changing it back to regular oil)

Dirty Harry · #5 (**permalink**) 03-02-2014, 03:23 PM

I also had a great sound at speed, but a disappointing sound at idle. I also had a huffing or puffing sound, more noticeable on one side. Last winter, I pulled the iron heads off, had them completely rebuilt and put it back together. The mid-range sound is the same, but the sound at idle is much better, even with my mild cam. Trouble was that I had a lot of recession of valve seats and wearing away of the valve faces to where there was almost no margin. New seats and several new valves helped. In the end, I probably could have gotten about the same results for a little more money with new heads, but I wanted to keep the ones I had.

Dwight · #6 (**permalink**) 03-02-2014, 08:41 PM

hard hit at idle is all in the cam and sidepipes.

I installed the Classic Cobra Pack on my Cobra. My small block sounds like a big block.

Classic Chambered Exhaust Inc. - Cobra
Dwight

DanEC · #7 (**permalink**) 03-03-2014, 04:48 AM

Quote:

Originally Posted by Dwight

hard hit at idle is all in the cam and sidepipes.

Dwight

And compression:

A lot of cam "and compression" together, will really make your engine hit hard at idle. You may not like some of the other attributes entirely, however.

Dwight · #8 (**permalink**) 03-03-2014, 06:55 AM

Yes I forgot about compression.
I think you can run more lobe separation and less compression and still get a hard hit at idle. Best to check with someone who understands cams.

I run Comp cam in my 354 (347) Cobra motor with .590 / .595 lift and a lobe separation of 112. Compression 10.67.
My stock Ford computer with a piggy back SCT chip makes it all work.
350 rwtq at 2500 rpm
great street motor but rough on the rear tires

Dwight

Mike I · #9 (**permalink**) 03-03-2014, 09:39 AM

Quote:

Originally Posted by DanEC

And compression:

A lot of cam "and compression" together, will really make your engine hit hard at idle. You may not like some of the other attributes entirely, however.

Agree totally with Dan's comments, the best sounding idle I ever had was a SBC in a '63 Vette with 12.5:1 CR, an off-road mechanical lifter cam and very minimal exhaust...but, as Dan states, it only made power above 6k and was a bear to drive on the street...

buddyg · #10 (**permalink**) 03-03-2014, 09:00 AM

Quote:

Originally Posted by Dwight

hard hit at idle is all in the cam and sidepipes.

I installed the Classic Cobra Pack on my Cobra. My small block sounds like a big block.

Classic Chambered Exhaust Inc. - Cobra
Dwight

These guys are saying 100hp and 100tq increase by just changing these??

Seems very optimistic?

mdross1 · #11 (**permalink**) 03-05-2014, 06:02 AM

Quote:

Originally Posted by Dwight

hard hit at idle is all in the cam and sidepipes.

I installed the Classic Cobra Pack on my Cobra. My small block sounds like a big block.

Classic Chambered Exhaust Inc. - Cobra
Dwight

This muffler design is the cats. I had a custom set of stainless mufflers made for our 155" Harley they are everything advertised especially the sound. Run them one way for performance and sound turn them 180 degrees they are a little quieter and flow a tad less.

Marc Wulf · #12 (**permalink**) 03-03-2014, 07:49 AM

Thanks Dwight
Checked out Classic Chambered Exhaust.
That's what I need.

Dwight · #13 (**permalink**) 03-03-2014, 08:19 AM

With my old side pipes I could be heard a mile and half away when I rev'ed to 6000. Got pics to prove this.
Very loud pipes.
I changed to the Cobra Packs but I bought 28" (4" longer) and 3" I.D. My old pipes were 24" x 2 1/2" I.D.
I wanted them to breath easy at 6000 but have a good sound at idle.

The longer pipe is quieter at idle. Not a tested theory but with 6 or 8 of my Cobra buddies who are around me every week, we all agreed.
Sounds like a big block at idle and good mellow sound at 2000 rpm cruising speed. I can talk to my passenger without screaming. Best of everything.
I also install a pair on a KC 408 and a KC 427/487. Great sound for Cobra!
Dwight
you can not see the large chunk of my butt that is missing. He was four blocks away and heard me. No ticket.

MaSnaka · #14 (**permalink**) 03-03-2014, 10:59 AM

I picked up 80 HP by changing to classic chambered 2 1/2" muffler. I also changed intake manifolds at the same time from a 390 performer to the RPM performer on my 390fe. I dynod before and after and was pleased with results. Classic chamber was great to deal with as well. My stock mufflers were very restrictive.

John

CzyCobra · #15 (**permalink**) 03-03-2014, 12:24 PM

Looks like I'll be picking up a set of these before summer

Dwight · #16 (**permalink**) 03-03-2014, 03:31 PM

I don't think I picked up 80 or 100 hp maybe 15 or 20. But I'm running a small block and I had 2 1/2" I.D. pipes with equal lenght headers and the correct lenght pipes for my motor / hp. So my HP/TQ gain was smaller.

Dwight

buddyg · #17 (**permalink**) 03-05-2014, 06:24 AM

Definitely on the list of mods if you can even pick up 20hp, more than that would be icing.