Mufflers for side pipes

[Cobra #3170]

Originally Posted by Gunner

I don't think you'd need to lose that much power. Exactly what are you running right now? Are they straight-throughs (cherry bombs)? And what engine and general build?

Current mufflers are Stainless Specialties ,straight through large ID about 2.75 but am not sure.

Engine: Shelby Aluminum Block, 14.7 to 1, raised port Blue thunder heads w/offset TD rockers. 498 CID, roller cam 287/292@.050 .780 lift, 2 1/8 primaries 3 1/2" collector, peak power 7600, peak torque 5500. I think the cam and compression are responsible for a majority of the noise. Flowmaster said I would lose power but could not give me a %. I thought someone might have tried them since they were developed for this market.

[Gunner]

Originally Posted by Cobra #3170

Current mufflers are Stainless Specialties ,straight through large ID about 2.75 but am not sure.

Straight-throughs are always going to be somewhere between WOW! and TOO DAMN LOUD, I SAID, TOO DAMN LOUD! They'll kill all the really irritating high-frequency noise but not much else.

You need at least some baffling or foldback to hold in the lower-freq engine noise. As noted, a little backpressure is a good thing.

You might be able to have a good muffler shop insert new cores in your existing pipes for a lot less than a full replacement of the muffler sections. A simple glass-packed single fold/baffle will reduce even that monster mill's noise to something well into WOW range.

You will likely need to retune the carb after the change. The backpressure will change airflow a bit.

[DanEC]

Originally Posted by Cobra #3170

I think the cam and compression are responsible for a majority of the noise.

You got that exactly right. Trying to quiet down that type of compression and a cam that peaks over 7000 rpm will be tough without strangling the motor to at least some degree.

[Stentor]

You might want to speak with Tom from Tom's Motorsports in Las Vegas regarding some of the pipes that he has fabricated for Cobras that are raced (reduce noise levels without losing too much power).

http://www.tomsmotorsportsinc.com/

[RICK LAKE]

Cobra #3170 You built an animal that will not like being contained. The high compression is a big part of the noise issue. you are about 150-175 pounds higher than motor with 10.0 compression. I only thing that might help is going to a under car exhaust system with 2 sets of mufflers on each side of the car. hemi mufflers where big in the old days, great flow but quiet to drive. I think it will be hard for you to find a side pipe setup to quiet El Monster down. If worst comes to worst, I would be happy to swap you a nice shelby motor for yours, with side pipes for the street. An Oval system will give you a little more ground clearance, just a thought. Rick L. Ps didn't you just take a cannon to a gun fight? That's the rumor, sound more like the truth.

[Ant]

I have seen multiple small diameter perf cores welded into a group fitted to race cars eg. if you have a 3" internal diameter muffler you can fit inside a group of 4 x 1.25" cores which run the length the muffler, a leading motorsport team claims this can reduce noise significantly and possibly up to 60% but I guess that varies and as mentioned in this post high compression is very hard to muffle!

I am going through a similar scenario with my 373 based cup engine and deciding on either 4 or 4.5" diameter outer case, and whether to use 3" or larger 3-1/2" internal perf core, I have the stainless screen material to make my own extra muffling cores. I notice on Vintage Motorsports cobras they use 3" turnouts which I think look better than the 3.5" drainpipes most people use, but I guess if you need a large core you dont need to restrict the end of the pipe.............!

[601HP]

I gotsda know; what are the HP and TQ numbers for that engine? I'd like to hear it bark!

David