The Stovebolt Site Forums The Shop Area General Truck Talk Need Advice: 6cyl Dual Exaust (mufflers)

Hi all,
I have a '57 3200 with a 235cui. I'm putting on Fenton dual intake with Fenton headers.
I would like to have a little sound coming from the tailpipes. Nothing to loud, just a nice sound. I'm unsure of the muffler to use. Any advice? Suggestions? (any sound clips are a plus!) rocklein@verizon.net THANKS!

With that setup I would want to use glasspack mufflers,maybe CherryBombs. they might be a little loud,depending on what level of exhaust noise you want.Also a set of turbo mufflers would be a little more quiet and give you a nice rumble.On my 65 with the Caddy engine I am running turbos and they just give the truck a nice powerful sound.On my 55 with a 350 SB I am running flowmasters ,also not too loud but a nice rumble,especially at idle.

Since the exhaust pulses alternate from one pipe to the other on an I-6 with a split manifold, some very irritating harmonics can be generated if a straight-through design muffler like a glasspack or a steelpack is used. You need a design that makes a couple of 180-degree turns with the gas flow inside the muffler. Putting a slightly larger-than-normal pipe diameter on the system like 2 1/2" in and out for both mufflers will take care of the back pressure, and stock-design baffled mufflers will control the noise. The low-restriction pipes will let a little sound escape without being annoying. I like to use two mid-1970's Cadillac mufflers, designed for enough capacity to carry the exhaust of a 500 cubic inch engine through one muffler. They've got 2 1/2" pipes in and out.
Jerry

I'd also suggest a crossover pipe. Without one you've got three cylinders exhausting from each of two pipes. I'm sure you've heard plenty of V-8s without crossover pipes, They sound like crap, and give up a significant amount of performance.

Remember the sound that the 1950's Formula 1 cars with straight sixes made? That's what I'd go for. Note that all of those exhausted into one manifold. A crossover pipe will give pretty much the same effect.

Well, exhaust sound is a subjective thing, each one has his/her own preference. Personally, I'm one old-timer that loves the sound of a Chevy or GMC 6 rappin' out through the gears. I liked it back in the 50's and I still like it.

I prefer old school when it comes to modifications. Old school (in CA where I grew up) was Fenton's or a split manifold, Smitty glasspacks (still available) and 2" or less piping. The longer the Smitty, the quieter the sound. And no one ran a crossover.
Run the tailpipes all the way out the back. Just my opinion.

CJ 7 mufflers have worked well for me, give a nice rumble.

On my 52 235 with Fenton's and Offy intake I run 2in pipe and 18in resonators and no cross over. The sound is awesome, nice blattt on acceleration and gurgle on deceleration. Very happy with it

I have Fentons on my GMC 248 with Turbo mufflers. Nice mellow sound and when you floor it there is a little noise. I like it.

Smitthys all day, 2" pipe, engine needs backpressure to run best. My 2 cents, Smitty

I am running stock mufflers and a split manifold on my 54 Bel Air. Has a nice subdued mellow sound.
Cleon

I'm a little surprised about your comment on backpressure making the engine run better. I'd always thought that negative backpressure would give best performance, another reason why I use crossover pipes.

Can you explain, please?

Was talking to an old timer about this very subject just the other day, and he said the best sound and performance would be with a set of glasspacks, or Smitty's, but the difference would be one would be just a tad bit shorter than the other. Makes for a very distinct bark from the 6 banger. I figure he knows what he's talking about. He's forgotten more about these old cars and trucks than I'll ever know. Been involved with racing since forever, both as a builder and a driver. Presently helping his son with an IMCA racer, and over the years they've enjoyed over 100 feature wins.

Waldo53 hit the nail on the head, with exhaust sounds being a subjective thing. I happen to run a pair of Cherry Bombs on my 235 using the stock ID 1-7/8" pipe so I didn't gut my low-end torque. My mufflers are mounted back under the bed and I can cruise in relative comfort without a lot of noise in the cab. But wait....I'm running a T5 and cruise at 2000 rpms at 70 mph. The problem is that if you are cruising at more than 2300 RPMs the Cherry Bombs will start their "BLATTT" and you'll be an unhappy cruiser.

I'm not saying that Cherry Bombs might not work well for you...just that what you use depends on some more factors than just what makes us happy with our particular setups. When the 235 gets to 2300+ rpms, in any gear, the straight-through Cherry Bomb is going to wake the dead. In the lower gears and in traffic you're going to have to light pedal it to avoid creating too much of a racket.

I've tried the Cherry Bomb Turbos, which like the Glass Packs had a great idle, but seemed to be a little too restrictive in the upper range, and also necked down some flowmaster 40's for the 2" OD pipe. They had a good idle sound but went back to the CB Glass packs.

If you're running stock gearing and will be cruising above 2300 rpms I'd suggest you consider try some CB Turbos and mount them as far to the rear of the cab/box as possible. They're about the least expensive muffler on the market and might be just the ticket.

Dave

Starkweather, My comment about backpressure relates to a low compression street engine. Back pressure is necessary for the best flow of incoming charge, exhaust cycle on a 4 cycle engine. A stock or mild engine is designed with cam, valve lift and timing to run with some back pressure. Of course, too much back pressure would be bad,like a plugged muffler etc. A more radical engine with higher compression ,big cam lobes, bigger valves, etc can benefit from headers, big pipes to scavenge exhaust. I was just reading in Street Rod mag about the ford Y block running best with 2 inch pipes and glasspacks vs full flow mufflers and big pipes. Hope this makes sense, there is alot of info on this subject out there!!

My front 3 cylinders on my 261 run though an ordinary stock manifold (including heat riser) which is cut off between the 2-3 and 4-5 exhaust ports. The rear manifold came from a cabover truck and this manifold exhausts just ahead of the bell housing, exhausting cylinders 4, 5, and 6. I am running a straight pipe from the front manifold in the stock location down the left framerail. The rear manifold makes a bend just behind the transmission and another bend to run down the right framerail. I temporarily ran straight pipes which stopped just behind the cab and that was WAY too loud. I had a couple flowmasters sitting around so I stuck them on the ends of the straight pipes and made some 'tips' that direct the exhaust down just ahead of the rear axle. This really quieted things down--almost too much. You can just start to hear it cackle a little about 2700 rpm, and I normally don't push it that hard. When the flowmasters die I think I'll go with glasspacks and get the pipes clear out to the rear. I wanted to wait on mounting exhaust pipes until I figure out a way to mount a spare under the bed, which means figuring out which wheel bolt pattern I decide to use (5X5 or 5X4.75)

I too am old school and prefer the sound of glasspacks and small pipes or no mufflers at all with dual on a six. Dual 1 3/4 pipes all the way out the back even without muffs is fairly quiet at idle, and stays that way until you open it up.

Devin

flowmaster 40's.

I'd read somewhere that a little back pressure would force some of the burnt gases from the exhaust back into the cylinder. I suspect this would have two effects. 1. Help heat the incoming charge, and 2. reduce the burn temperature of the new charge, since the exhaust gas has already had all of the fuel burnt out of it and would just act like inert gas.

Is this what you are talking about?

Yeah,, that says it better than I was able to !! There is alot of physics here, and it can get pretty complicated. The engineers who designed these things are way smarter than I will ever be, so I just try tokeep things simple.

I put glasspacks on my truck with 1 7/8" pipes. I thought it was too loud. I replaced the packs with Flowmaster 40's and it has a nice sound. But as has been said, each person's ear is a little different. Listen to what others have done until you find something you like. I had a guy recently that was shocked when he opened the hood and saw a 235. He swore it was a 283 as I pulled away from him last time he saw the truck.

Patrick's stainless steel exhaust system (if you can get it). Sounds mellow, fit great and looks super. Some pics are in my webshots albums.